Research Connections

Addressing tomato fruit susceptibility and fungicide timing to improve the management of target spot, caused by Corynespora cassiicola: Part 1

Problem
Target spot, caused by the fungus Corynespora cassiicola, is one of the costliest to the industry due to its impact on marketable yield at harvest and potential to cause additional losses during post-harvest packing operations. No commercially available host resistance exists for target spot. Tomato production relies on fungicide applications for disease control, which raises concerns over the development of fungicide resistance.

Prior studies evaluated 117 C. cassiicola tomato isolates collected from tomato production fields in Florida and identified >90% of the isolates were resistant to QoI fungicides (FRAC 11) and 75% were resistant to one or more SDHI fungicides (FRAC 7), while approximately three-quarters of the conventional fungicides labeled for target spot are QoI or SDHI fungicides.

Increased selection of resistance to the respiration inhibitors threatens the effectiveness of many fungicides available for target spot control. In addition, label changes proposed by the EPA for chlorothalonil would greatly limit the use of this contact fungicide for many crops produced in Florida (Docket EPA-HQ-OPP-2011-0840). The loss of contact fungicides like chlorothalonil and mancozeb would pose a challenge for many vegetable crops, since these economical products are commonly used early in the crop cycle as general maintenance sprays and as either a tank-mix or rotational partner for managing fungicide resistance against site-specific fungicides like the respiration inhibitors.

Trial 1. Determining tomato fruit susceptibility to infection by C. cassiicola during fruit development

Field trials at GCREC were established to determine susceptibility of tomato fruit to C. cassiicola at different stages of fruit development.

The results demonstrate that regardless of inoculation date, fruit became progressively more susceptible as they develop and ripen (Figure 3). On average, disease development on fruit inoculated 7 and 14 DPI required 14 days; while fruit inoculated at 21 and 28 DPI only required 7 days. We also observed target spot development on mock-inoculated fruit, but at a much lower frequency. Overall, these results are not too surprising, since packinghouses often observe that harvested green fruit exhibiting minor pinpoint lesions often progress into large lesions during the ripening process, leading to breakdown.

In addition, the data shows the difference in virulence between the two C. cassiicola isolates, with higher percentage of fruit inoculated with isolate 93 developed lesions within 7 to 14 days compared to isolate 2 (at 14, 21, and 28 DPA). Also, on average fruit lesions produced by isolate 93 were 50% larger than those produced by isolate 2 (data not shown).

Regarding target spot developing on mock-inoculated fruit, developing fruit lesions sporulate profusely over time (see Figure 2). As such, the infection of the mock-inoculated fruit might be due to secondary infection from inoculated fruit, since many of the mock-inoculated fruit were often next to fruit inoculated with C. cassiicola out of convenience (easier to find as plant developed). Follow-up trials will inoculate fruit on greenhouse-grown compact-growth hybrid (CGH) plants to limit the potential of cross-infection.

Attempts were made to inoculate fruit without mechanical injury (puncturing) but were unsuccessful in the field. Hence, it is not possible to differentiate whether C. cassiicola can cause a latent infection (non-symptomatic infection) versus a quiescent infection (a visible infection that is not expanding). Subsequent greenhouse trials may help separate this difference, and test whether our observations are merely an artifact of our inoculation method. The decision to use field rather than greenhouse-grown plants was due to the large number of fruits required to conduct the experiment. Future greenhouse experiments can focus on a smaller number of inoculation timepoints, which will benefit work to evaluate differences in C. cassiicola aggressiveness on fruit and fruit susceptibility of breeding materials.

If you have any other questions regarding Target Spot or other vegetable diseases, please feel free to reach out to Dr. Gary Vallad.

 

Past Research Connections

 

 

• Read: Exploring Methods to Enhance the Soil Environment for Increased Resiliency in Vegetable Production

  Fumigation is a standard practice for vegetable production control of some soilborne plant pathogens and some weeds. However, the efficacy of fumigants can vary and it’s not clear how fumigants impact the other microbes in the soil (i.e. the microbes that are not pathogens). Many soil bacteria and fungi can be beneficial for plant growth, so understanding if these beneficial microbes are still in the soil after fumigation, and how long it takes for them to return to the soil, could help optimize or improve fumigation practices. Dr. Sarah Strauss, along with weed scientist Dr. Nathan Boyd, plant pathologist Dr. Gary Vallad, and soil scientist Dr. Mary Lusk, have been working on answering these questions through a USDA-NIFA grant. One of the early findings of their work is that fumigation with chloropicrin results in increases in bacteria and fungi, such as Bacillus and Trichoderma, that might be important in disease control and plant growth.

  One of the potential limitations to altering the microbes that are present in Florida soils is the low amount of organic matter in our soils. Planting cover crops or applying compost are common methods for increasing organic matter, and thus resources for soil microbes. Given that we are seeing increases in potentially beneficial bacteria and fungi with fumigation, we were curious whether improving the resource availability for soil microbes through compost or cover crops before fumigation would result in greater increases in beneficial microbes after fumigation. Many of these potentially beneficial microbes can go dormant or form spores to survive conditions such as fumigation, and increasing the resources available to them through compost or cover could magnify the benefits to disease suppression. In addition, certain cover crops are known to deter nematodes, and thus planting them prior to vegetable production might help control those pests. Dr. Sarah Strauss was recently awarded a new grant from USDA-NIFA to address these questions for fumigants commonly used in Florida tomato and strawberry production. In addition, the project will also examine how changes in non-target soil microbes might impact the suppression of soilborne plant pathogens, nutrient availability, and weed growth. Vegetable horticulturalist Dr. Pavlos Tsouvaltzis, plant pathologist Dr. Gary Vallad, and nematologist Dr. Johan Desaeger are joining her on the project to help address these questions.

  
  Cover Crop and Compost Trial

  Interested in learning more about fumigant impacts on soil microbes or participating in our trials? Contact Dr. Strauss and Craig Frey for more information.

  
  
  

 

• Read: Corn Silk Fly Ecology Research

  Euxesta stigmatias, Euxesta eluta, and Chaetopsis massyla are three picture-winged flies known as corn silk flies. These flies continue to be a major problem for sweet corn growers in southern Florida. Adults lay eggs on sweet corn silks and husks, and maggots feed on silks and kernels where they are protected from insecticides and natural enemies. Thus, current corn silk fly management targets adults with insecticides to prevent egg deposition.

  Corn silk flies typically become more challenging to control as the growing season progresses from the winter to the spring. However, the factors contributing to increased management difficulties have not been identified. On-farm research funded by a USDA NIFA Specialty Crop Research Initiative project led by Dr. Marcio Resende in the UF/IFAS Horticulture Department was initiated in 2024 to assist in determining corn silk fly population trends and identifying factors that influence pest severity.

  Eighteen sites were selected on commercial farms and sampled from late winter to early summer 2024 to determine corn silk fly adult abundance and species composition throughout the peak of the production season in southern Florida. Two major crop consulting companies and four sweet corn growers assisted with research site selection.

  Each site included a sweet corn field, or a group of sweet corn fields, planted between late December and early March. Sampling at each site was initiated in early February and was completed in early June. Thus, sampling was conducted before planting for many sites, and continued until after harvest for all sites. At each site, five corn silk fly traps were deployed 250 ft apart along a transect running 15-30 ft parallel to the sweet corn habitat. Corn silk flies captured in the traps were collected every 7-14 days, and the phenology of the sweet corn habitat and surrounding landscape within a 0.5-mile radius were characterized.

  5,517 corn silk flies were captured (51.5% Euxesta stigmatias, 44.9% Euxesta eluta, 3.6% Chaetopsis massyla). Formal data analyses have not been conducted yet. Nevertheless, data show that trap captures for the three species combined increased as much as 70-fold from February to May (Fig. 1). In addition, the average proportion of E. stigmatias increased from 11% in February-March to 53% in April-June.

  Fig. 1. Areawide corn silk fly trap captures in the Everglades Agricultural Area	Silk Fly Adult (E. Stigmatias)

  This on-farm research is the first to document a general increase in corn silk fly numbers, as well as a relative increase in E. stigmatias numbers, during the sweet corn growing season. This increase in abundance of corn silk flies in general, and of E. stigmatias in particular, partially explains increasing corn silk fly management issues during the late spring because E. stigmatias has exhibited reduced susceptibility to insecticides.

  Substantial increases in corn silk fly numbers often followed the termination of the sweet corn crop or the presence of field corn in the vicinity of the traps. Observations did not suggest that harvest of neighboring sugarcane fields contributed to an increase in corn silk fly numbers. However, high variability among sites was observed, suggesting that multiple interacting factors influence corn silk fly population dynamics.

  Additional data collection during the next two growing seasons and further data analysis are expected to determine the contribution of factors influencing corn silk fly pest severity, which will assist with the implementation of production practices minimizing the build-up of damaging corn silk fly populations.

  If you have any questions regarding pest management in vegetable production in the Everglades Agricultural Area, please feel free to reach out to Dr. Beuzelin for further information.

  
  
  

 

• Read: Improving S-Metolachlor Efficacy and Crop Safety in Plastic-Mulched Tomato Beds

  The discontinuation of methyl bromide has led to a decline in broad-spectrum weed suppression, causing challenges for Florida's vegetable producers, especially with persistent weeds like purple and yellow nutsedge. These weeds can penetrate plastic mulch, have resilient tubers, and spread rapidly through rhizomes. To address this issue, a multi-strategy approach is necessary. Integrating pre-emergence herbicide application alongside fumigation could greatly enhance weed suppression in plasticulture beds. While pre-emergence herbicides effectively control nutsedge in vegetable production under plastic mulch, concerns about crop phytotoxicity and subsequent stress the crops may limit their application. One of the primary focuses of Dr. Kanissery's program is to enhance the utility and crop safety of pre-emergence herbicides in vegetable plasticulture production.

  Although the co-application of pre-emergence herbicides with fertilizers has been explored in row crops, its potential in vegetable plasticulture systems remains largely unexplored. In a study funded by the FDACS specialty crop block grant, Dr. Kanissery's team evaluated the efficacy and safety of the pre-emergence herbicide S-metolachlor (active ingredient or a.i in products like Dual Magnum II) in tomato plasticulture. Field trials at the University of Florida's Southwest Florida Research and Education Center in Immokalee involved applying S-metolachlor at the recommended rate (1 kg a.i ha-1) on raised beds before laying plastic mulch. The herbicide was either applied alone as sprays or side-dressed onto beds coated with slow-release chelated iron fertilizer. Previous studies have examined the use of iron supplements alongside herbicides to reduce herbicide toxicity in crops. Furthermore, prior reports have shown that fertilizers, such as chelated iron, hold potential as slow-release agents for pre-emergence herbicides like S-metolachlor.

  Results showed that using S-metolachlor alone effectively reduced purple nutsedge density compared to the untreated control in all the trials. Combining S-metolachlor with chelated iron also resulted in a reduction of purple nutsedge density compared to the untreated control. These treatments did not negatively affect chlorophyll content or crop yield compared to the control.

  Notably, tomato yield significantly decreased with increased purple nutsedge density in the beds. Overall, the study suggests that using S-metolachlor alone or in combination with slow-release fertilizer effectively reduces purple nutsedge infestation in plastic-mulched raised beds without compromising tomato health and productivity.

  Dr. Kanissery and his team are also investigating the synergistic effects of different pre-emergent herbicide products when applied as tank mixtures under plastic mulch. This approach could potentially reduce herbicide rates and manage weed tolerance more effectively, particularly for tough weeds like nutsedge.

  Dr. Kanissery has new research and recent results on Improving S-Metolachlor Tolerance in Tomato Transplants Through a Novel Seed Treatment-Based Herbicide Safening - To enhance weed control in plasticulture beds, especially against persistent weeds like nutsedge, a multi-strategy approach combining pre-emergence herbicides with fumigation is essential. However, concerns over potential crop injuries from pre-emergence herbicides limit their use under plastic mulch. This research explores how safeners such as benoxacor and fenclorim protect tomato transplants from damage caused by S-metolachlor (the active ingredient in Dual Magnum), a commonly used pre-emergence herbicide for controlling nutsedge in plastic-mulched tomato beds. The findings suggest that these safeners, when applied as seed treatments, may enhance the protection of tomato transplants by potentially increasing the activity of glutathione S-transferase (GST), thereby reducing stress caused by S-metolachlor.

  The figure below illustrates the positive effects of Benoxacor and Fenclorim safeners, used as seed treatments, on the plant vigor and root mass of tomato plants grown in soils treated with pre-emergence herbicide S-metolachlor compared to NO-safener treated controls

  If you have any questions regarding weeds in vegetable production or the use of herbicides for their management, please feel free to reach out to Dr. Kanissery for further information.

  

  
  
  

 

• Read: Grant for Sustainable Anthracnose Management (SAM) in Cucurbits

  Drs. Gary Vallad, Geoffrey Meru, and Pamela Roberts are UF collaborators on a recently funded, multi-state grant led by Dr. Bhabesh Dutta, University of Georgia, addressing Sustainable Anthracnose Management (SAM) on cucurbits. The grant focuses on anthracnose as an emerging threat to watermelon and cucumber. The overarching goal of the grant is to reduce economic losses from anthracnose through tools and information developed by the grant to increase grower profitability.

  Cucurbit anthracnose is caused by the fungus Colletotrichum orbiculare and other Colletotrichum species. Anthracnose on watermelon and cucumber has been of growing importance in Florida with more outbreaks detected in south and central production fields. Losses from anthracnose are caused by plant defoliation from lesions on leaves, peduncles, and stems. Fruits with lesions are non-marketable.

  The Florida team will work on grant objectives addressing the pathogen, management, and host resistance. Roberts will conduct field surveys, fungicide sensitivity, pathogenicity, and race typing. This work will be used by grant team members doing population genomics and diagnostic assay development. Meru will screen commercial cucurbit varieties and plant introduction lines for resistance. Vallad will conduct field trials testing fungicide efficacy and environmental production practices. Additional grant team outputs will include multistate extension efforts and economic assessments on grant outcomes.

   

  Anthracnose on watermelon fruit photo credit: Dr. Pam Roberts	Anthracnose on watermelon leaf photo credit: Dr. Katherine Hendricks

 

• Read: Common purslane management in leafy vegetables

  Common purslane is the most problematic and difficult to control broadleaf weed in leafy vegetables, including lettuce. Prevalence of common purslane in the Everglades Agricultural Area (EAA) where leafy vegetable production occurs is attributed to its prolific seed production, ability to grow under warm moist soils presently prevalent throughout most of the season, and tolerance of management practices. Common purslane has shown tolerance to imazethapyr, the only herbicide for broadleaf weed control in leafy vegetables in the region. Mechanical cultivation used to supplement chemical control does aggravate common purslane’s persistence because of the ability of its fragments chopped during cultivation to regenerate and reinfest the crop. This has resulted in growers relying on costly hand weeding to supplement chemical control. Thus, it is important to develop management programs for growers that are less dependent on hand labor. Consequently, alternative efficacious herbicides with activity on common purslane and other broadleaf weeds are needed to minimize negative effect of weeds on leafy vegetables production.

  Our preliminary data indicate that pendimethalin can potentially be safely used to mitigate negative effects of common purslane on leafy vegetables. Pendimethalin is a dinitroaniline herbicide primarily used for control of grass and certain broadleaf weeds. We are presently evaluating (i) common purslane control programs using pendimethalin (at 1 and 2 lb ai/acre) in combination with other weed management strategies, (ii) the effect of temperature and moisture on common purslane recruitment processes, and (iii) the persistence of pendimethalin in leafy vegetable production soils in the EAA. To maintain high yields, quality, and economic viability in leafy vegetable production, development of an integrated common purslane management is important for growers in the EAA.

  

  Common purslane in a lettuce field.

 

• Read: One of the Main Pests that Florida Farmers Face: Plant-Parasitic Nematodes

  Dr. Johan Desaeger’s Gulf Coast Nematology laboratory studies plant-parasitic nematodes which are one of the main pests that Florida farmers face. The lab works primarily on developing integrated nematode management strategies for reducing nematode impacts. This includes evaluating nematicides, cover crops and resistant cultivars, as well as studying the impact of these practices on soil health and quality and natural nematode suppression.

  Ongoing research projects include an FDACS-funded project in collaboration with Dr. Mary Lusk evaluating vegetable farm cover crop practices to improve nematode management, nitrogen utilization and water quality. Cover crop treatments include pure stands and mixtures of sunn hemp, sorghum sudangrass and southern pea. Previous research has shown that sunn hemp and sorghum sudangrass are poor hosts to many species of root-knot nematodes and good cover crop options for Florida vegetable farmers (Table 1). The new project seeks to quantify how these cover crops and their mixtures not only affect root-knot nematodes but also other nematode populations, leaching and availability of nitrogen, and yield of tomato and zucchini.       

  Table 1. Nematode reproduction on four cover crops (and tomato) eight weeks after inoculation with the four most common root knot nematode (RKN) species in Florida vegetable fields (Meloidogyne arenaria, M. enterolobii, M. incognita, M. javanica).

  

  Another project funded by the Florida Tomato Committee is investigating the prevalence of guava root-knot (Meloidogyne enterolobii) and stubby root (Nanidorus minor) nematodes in Florida tomatoes. Both nematodes are common in Florida fields but remain relatively unknown. The damage from guava root-knot nematode can be severe but indistinguishable from other root-knot species. What makes guava root-knot more dangerous is that this species will break currently available root-knot nematode resistance in tomatoes. The damage that stubby root nematodes cause is less clear, but this nematode may (or may not) be associated with yellow top symptoms in mature tomato plants. We are still investigating this, as well as the possibility that stubby root nematodes could transmit a virus (as is the case in potatoes where they cause tuber corky ringspot). This work is done in collaboration with USDA (Dr. Scott Adkins).

  If you have any concerns about nematodes in your fields, don’t hesitate to reach out to your local county Extension agents or to jad@ufl.edu. We’re there to help.

  Sunn hemp cover crop (Crotalaria juncea)	Guava root knot nematode galls on tomato	Yellow top on tomato (possibly associated with stubby root nematodes)

   

 

• Read: The Value of Integrating Data from Nondestructive Assessment of Plant Physiology in Real Time Monitoring of Vegetable Crops' Performance
  Growers are already aware of the importance of optimizing soil and water management practices, and are adopting strategies to mitigate adverse weather impacts, ultimately aiming to enhance sustainable vegetable farming practices. Therefore, regular soil analysis for mineral content and monitoring soil moisture, water quality, air temperature, relative humidity and solar radiation are common practices.

  However, beyond the above, information from actual plant responses should be integrated in data-driven crop production management strategies. In other words, growers need a new approach to confirm in real-time that plants are efficiently assimilating water and nutrients and rapidly prevent any imminent disorders.

  There are several tools nowadays to achieve that by using portable equipment that reveal the plants’ physiological state capturing nondestructive measurements on leaves:

  • Stomatal conductance: refers to the rate at which CO₂ enters and water vapor exits the leaf through stomata. It influences photosynthetic and transpiration rates and may relate to the optimization of water use efficiency and nutrient uptake.
  • Chlorophyll content: Indicative to photosynthetic rate, it is also closely linked to the nutritional status of the plant, especially nitrogen which is a main element of chlorophyll structure, and its deficiency can be detected as chlorosis (yellowing of leaves).
  • Chlorophyll fluorescence: the emission of light by chlorophyll molecules during the return from an excited to a ground state. It may be an indicator of plant stress, such as drought, heat, or nutrient deficiency, which impacts photosynthesis by damaging the photosynthetic apparatus or reducing its efficiency.
  • Spectral reflectance: energy that is reflected by the plant at different wavelengths either in the visible (400-700 nm), or near infrared (700-2,500 nm) region of the electromagnetic spectrum. Specific wavelengths or combinations of wavelengths (e.g., NDVI - Normalized Difference Vegetation Index) are used to assess plant health and vigor, or even detect individual components, such as water content, or specific minerals and organic compounds.

  By combining these measurements with soil and weather data, a more precise monitoring of plant health and early detection of nutrient deficiencies can be accomplished. This approach holds great potential for the growers, although currently these techniques cannot be very easily adapted, due to the high cost of purchasing the equipment and the advanced knowledge which is needed for processing the generated data. More research is needed to improve the current scientific knowledge and when consistent results confirm the reliability of the approach, the market will balance the needs of the agricultural community.

  This is the objective of a funded project ‘AI-enabled plant phenotyping for novel nutrient management in tomatoes’ under the collaboration of Dr. Pavlos Tsouvaltzis and Dr. Yiannis Ampatzidis, in order to develop an Artificial-Intelligence tool that will help growers to adjust nutrient supply based on nondestructive, remote sensing, on-ground and above ground techniques, monitoring the physiological status of plants.

  

  Figure 1. Tomato plant (A) and measurements of stomatal conductance and chlorophyll fluorescence (B), chlorophyll content (C), and capturing of spectral reflectance on a leaf (D). Visible to near infrared spectroradiometer (E) and a typical spectral curve of a healthy plant at 350-2,500 nm (F).

   

 

• Read: Research Update on the Management of Vegetable Insect Pests in Miami-Dade County
  Dak Seal's Entomology Team at the Tropical Research & Education Center in Homestead, FL is addressing the development of a management program for controlling melon thrips (Thrips palmi), Asian bean thrips (Megalurothrips usitatus), pepper thrips (Thrips parvispinus), pepper weevil (Anthonomus eugenii), and diamondback moth (Plutella xylostella).

  A preliminary study was completed to start developing a management program for controlling Thrips parvispinus in finger hot pepper. Other trials are on-going and results will be shared at a later date. Two studies were conducted in commercial pepper fields in Miami-Dade County, FL, to evaluate the efficacy of various insecticides for controlling T. parvispinus. The fields were planted to finger hot chili pepper in May 2023. Pepper plants were set on raised beds covered with white-on-black plastic mulch. Plant spacing within the beds was 2 feet and in between beds was 6 feet. The fields were managed by using standard practices as mentioned in the Vegetable Production Handbook of Florida. Various insecticide treatments and their rates/acre used in these studies are shown in the tables. Treatment plots consisted of 10-feet-long 2 beds and were arranged in a randomized complete block design replicated 6 times. In both fields, treatments were applied 3 times on 28 Jun, 8 Jul, and 15 Jul 2023 at weekly intervals delivering 50 gpa using a backpack sprayer at 30 psi. Evaluation was made by randomly collecting 10 full-grown young leaves from the top canopy of pepper plants 24 h after each application. Leaf samples were transported to the laboratory and washed with 70% ethanol to separate thrips and identified species using a binocular microscope at 10× magnification. Data were statistically analyzed using SAS Proc. GLM after square root transformation, and means were separated by Duncan multiple range test. Untransformed means were presented in the tables.

  Thrips parvispinus abundance was medium during the first study. On the first sampling date, all insecticide treatments in the first study, except Minecto Pro, significantly reduced T. parvispinus adults when compared with the untreated control (Table 1). On the second sampling date, the mean number of T. parvispinus adults was significantly fewer in all treated plants than in the untreated control. However, Sivanto-treated plants did not differ from the untreated control in the mean number of adults. On the third sampling date, all insecticide treatments significantly reduced T. parvispinus adults on pepper plants. The mean number of T. parvispinus adults/sample across all sampling dates mirrored the third sampling date. In a second study, Plinazolin, a new Syngenta insecticide that is currently undergoing EPA review, significantly reduced T. parvispinus as averaged from 3 sampling dates (Fig. 1).

  Table 1.

  Mean number of T. parvispinus adults/leaf sample

  Treatments	Rate [oz]/acre	First sample	Second sample	Third sample	Mean
  Radiant SC	8.0	4.25bc	0.67b	0.67b	2.10b
  Minecto Pro SC	10.0	5.25ab	0.00b	1.33b	2.50b
  Sivanto SL	21.0	3.25bc	1.67ab	1.33b	2.20b
  Lannate LV	36.0	3.00bc	1.67ab	1.67b	2.20b
  Torac EC	21.0	2.25c	0.67b	0.00b	1.10b
  Novaluron EC	12.0	1.75c	0.00b	0.00b	0.70b
  Untreated Control		8.75a	3.00a	4.33a	5.70a
  P value		0.002	0.038	0.019	0.0002.

  Means within a column followed by the same letter(s) do not differ significantly (P > 0.05, DMRT).

  Means between bars with the same lowercase letter do not differ statistically (P > 0.05; DMRT).

  Figure 1.

  

  Means between bars with the same lowercase letter do not differ statistically (P > 0.05).

  This study provides preliminary information about combating an initial infestation of T. parvispinus in commercial pepper fields.¹

   

 

• Read: Research Update on the Emerging Disease: Tar Spot of Corn in Southern Florida
  Effective disease management remains a paramount concern for growers in every growing season. The introduction of tar spot disease to the United States in 2015, swiftly followed by its appearance in Florida's fields in 2016, has directed focused research efforts led by Dr. Katia Xavier and her team. In 2022, the Foundation for Food & Agriculture Research (FFAR) recognized the urgency of the situation and awarded a Rapid Outcomes from Agricultural Research (ROAR) grant. One of the overarching goals was to unravel the epidemiological factors and genetic diversity of tar spot in the state.

  The research initiative commenced with a thorough survey of maize fields across Florida to gauge the incidence (number of infected plants in a given field) and severity (percentage of infected leaf area) of tar spot. The results revealed a promising trend, with the incidence and severity of tar spot notably lower than in previous years. Out of the 36 fields surveyed, 23 exhibited no tar spot, and 4 fields had severity below one percent. Even in the fields where incidence was above 50%, the severity ranged only between 5 to 12%.

  Symptomatic leaves were collected from all fields with tar spot to study the pathogen’s population. Preliminary findings from this study provided a crucial insight: all instances of tar spot on maize were caused by the fungal species Phyllachora maydis. This valuable knowledge is guiding the refinement of strategies for effective tar spot management.

  Beyond identifying the causative pathogen, understanding the dissemination and survival dynamics of P. maydis is pivotal. Dr. Xavier and her team conducted a survival study burying tar spot-symptomatic corn leaves in muck soil from the Everglades Agricultural Area, and rocky soil from Miami-Dade County, periodically assessing germination of tar spot spores. This revealed low levels of germination during the months of May through September. Whereas further assessments during cooler months are warranted, this initial insight suggests the current cultural practices performed by South Florida sweet corn growers such as tillage is a viable management option for controlling this disease.

  Picture of corn leaf infected with tar spot:

  

  This ongoing work on tar spot highlights its significance. If you have encountered this disease, we encourage you to reach out to Dr. Xavier (kvianaxavier@ufl.edu) or your local county Extension agent, contributing to the collective effort to mitigate the potential impact of tar spot on south Florida sweet corn.

 

• Read: Integrated Management of Soilborne Pathogens Impacting Vegetable Production in Florida
  Soilborne pathogens can cause significant yield losses to vegetable production. Their ability to survive in soil for long periods of time and broad host range can make management challenging. Growers have long relied on soil fumigation to manage soilborne pathogen populations. However, soil fumigation only provides a temporary reduction in pathogen levels, which for diseases like Fusarium wilt of tomato only delays symptom development. Supplemental fumigant applications to the edges of beds or deeper within the soil profile can improve management. However, increasing fumigation costs have many growers looking for ways to trim their fumigant rates. Dr. Vallad’s program is investigating several strategies to improve the management of soilborne pathogens through the use of fungicides (Table 1) and biopesticides.

  Table 1. Evaluation of drench and drip applications of adepidyn, fludioxanil, and Miravis Prime for the management of Fusarium wilt on tomato.
  Treatment, rate/A (applic.) z	XL yield (lbs/plot)y		Disease Incidence (%)
  Non-treated control	34.4	bc	82.6	a
  Adepidyn, 13.7 fl oz (drench 0, drip 2)	45.0	ab	40.7	bc
  Adepidyn, 11.5 fl oz (drench 0)	46.9	a	56.8	abc
  Fludioxanil, 8 fl oz (drench 0)	30.4	c	63.0	ab
  Miravis Prime, 15.4 fl oz    (drench 0, drip 2)	43.3	ab	47.1	abc
  Miravis Prime, 15.4 fl oz (drench 0)	45.4	ab	53.9	abc
  EXP 1, 11.4 fl oz (drench 0)	45.9	ab	45.7	abc
  Fludioxanil, 8 fl oz (drench 0);    EXP 1, 11.4 fl oz (drench 0)	42.1	abc	16.9	c
  Non-inoculated control	34.4	bc	32.1	bc
  z Rates are based on a row acre, with drip and drench applications (applic.) Made at plant (0) or two weeks (2) after planting. y Extra-large (xl) fruit yield (20 ft plot) was hand-harvested twice at the end of the trial.

   

  Dr. Vallad is also working with a team of researchers at USDA-ARS, University of California-Davis, and Pennsylvania State University to develop molecular-based methods for improved diagnostics of Fusarium pathogens on tomato and to monitor their populations in agricultural soils. The ability to differentiate pathogenic from non-pathogenic forms of Fusarium oxysporum will allow Dr. Vallad’s program to address the impact of cultural practices, such as cover crop rotations, fallow periods, and soil inputs on pathogenic Fusarium populations. 

  

  FIGURE 1. Tomato plants exhibiting classic symptoms of Fusarium wilt. Initial chlorosis and wilting of foliar tissues is typically asymmetrical, beginning with lower leaves and progressing upwards over time. Vascular discoloration can be observed in lower and upper symptomatic stems of plants. As wilt progresses, foliage becomes necrotic leading to plant death. 

  Genetic crop resistance is another option but limited to certain crops and to select soilborne pathogens, such as the available resistance to all three known races of Fusarium wilt in tomato. The deployment of disease resistant crop varieties is the most effective means to manage any disease. However, a recent breakdown in commercially available resistance to Fusarium wilt race 3 has raised concerns, since many tomato growers have adopted resistant varieties throughout the state. Dr. Vallad’s program would like growers and consultants to pay special attention to those tomato fields with Fusarium wilt race 3 resistant cultivars for any symptoms of Fusarium wilt (Figure 1). Growers and consultants are encouraged to alert Dr. Vallad (gvallad@ufl.edu or 813-419-6577) if they observe evidence of Fusarium wilt on Fusarium wilt race 3 resistant tomato cultivars or are interested in participating in future studies focused on the management of soilborne pathogens. 

 

• Read: A New Invasive Thrips Impacting South Florida Pepper Production: Thrips parvispinus

  First detections
  Thrips parvispinus is an invasive polyphagous thrips impacting vegetable and ornamental productions. It was first detected in the continental U.S. in a greenhouse in Orange County, Florida in August 2020. The insect was observed in the landscape in Miami-Dade County in early 2022, and on a gardenia hedge on Palm Beach Island in the spring of 2022 (Fig. 1). Samples collected in November 2022 in a pepper field in eastern Palm Beach County were confirmed as T. parvispinus by FDACS-DPI. This was the first record of an established population in a vegetable field (Fig. 2, 3).

  Fig. 1. T. parvispinus injury on gardenia on Palm Beach Island.
  Fig. 2. First observation of T. parvispinus infesting a pepper field in Palm Beach County.
  Fig. 3. Deformed pepper plant due to T. parvispinus feeding.

  Identification
  T. parvispinus females and males differ in size and color. The females are larger and have a yellowish-brown thorax and a black or dark brown abdomen (Fig. 4). The males are yellowish and smaller than the females. All leg segments are light colored. The third and the base of the 4^th and the 5^th antennal segment are light colored. An in-depth identification guide can be found here: https://commercialveg.ifas.ufl.edu/identification-resources/. 

  
  Fig. 4. T. parvispinus female. 

  Field observations in Palm Beach County
  In December 2022, commercial pepper fields were visited in East Palm Beach County with a crop consultant to observe injury and assess infestations. All life stages of T. parvispinus were found on all parts of the pepper plants, including flowers and fruits (Fig. 5, 6). Heavily distorted leaves and flower buds resembling broad mite injury were observed (Fig. 7). T. parvispinus injury caused substantial economic losses in these pepper fields.

  Fig. 5. T. parvispinus females on a pepper flower.
  Fig. 6. T. parvispinus injury on a pepper.
  Fig. 7. Deformed pepper plant due to T. parvispinus feeding.

  In the spring of 2023, T. parvispinus specimens were collected for the first time on cucumber, yellow squash, and zucchini (Fig. 8, 9). High numbers of adults and heavy feeding injury were observed on cucumber leaves. However, fruits only showed minor cosmetic damage (Fig. 10). T. parvispinus was also identified in a snap bean field by collecting flowers and leaves. Potential damage due to T. parvispinus on snap bean is still unknown.

  Fig. 8. T. parvispinus females feeding on a cucumber leaf. Photo by Joel Allingham.
  Fig. 9. T. parvispinus females on a squash flower.
  Fig. 10. T. parvispinus feeding injury on cucumber.

  Communication with stakeholders
  Timely communication with stakeholders is crucial upon the first detection of an invasive species. In December 2022, shortly after T. parvispinus was confirmed in a commercial pepper field in Palm Beach County, an information exchange virtual meeting was organized to give an update on the T. parvispinus situation for crop scouts. Scouts were asked to report and send suspected T. parvispinus specimens to extension agents Anna Mészáros and Craig Frey for preliminary identification and before submission to FDACS-DPI for identification confirmation. Participants were encouraged to report detections to the South Florida Pest and Disease Hotline. T. parvispinus updates were presented via multiple platforms such as extension webinars and vegetable seminars at the Florida Citrus Show and Citrus Expo.

  T. parvispinus distribution
  The South Florida Pest and Disease Hotline newsletter has been a crucial tool of our extension program to communicate the spread and population dynamics of pests during the vegetable season (Fig. 11.). As of July 2023, T. parvispinus had been intercepted in nurseries and stock dealers across the state. However, it was confirmed established in the landscape only in five counties (Lake, St. Lucie, Martin, Broward, Palm Beach, Miami-Dade) (Fig 12.). In Palm Beach County, T. parvispinus has been found on pepper, snap bean, cucumber, squash, and zucchini. Among these crops, pepper suffered the most significant damage. Sunn hemp flowers were also sampled, but no T. parvispinus were observed.

  Fig. 11. Infestation levels of T. parvispinus reported by Pest and Disease Hotline contributors in South Florida, April 2023.
  Fig. 12. T. parvispinus surveys by FDACS-DPI as of July 2023.

  Management in vegetable crops
  Scouting and early detection are important. This fall, various traps have been set up in vegetable fields in Palm Beach County to monitor T. parvispinus populations in order to help growers with insecticide application timings (Fig. 13-15). So far, T. parvispinus populations seem to be extremely low in Palm Beach County vegetable fields.

  Fig. 13. Yellow and blue sticky traps are used in vegetable fields for thrips population monitoring.
  Fig. 14-15. Yellow and blue sticky traps along with pan traps are used for thrips population monitoring.

  Common foliar insecticides with thrips activity (see table below) might be considered for T. parvispinus management. However, this is NOT a formal recommendation because we do not have reliable efficacy data for T. parvispinus control on vegetables.

  Product	IRAC MoA	Active Ingredient(s)
  Lannate	1A	Methomyl
  Assail	4A	Acetamiprid
  Radiant	5	Spinetoram
  Agri-Mek	6	Abamectin
  Torac	21A	Tolfenpyrad
  Exirel	28	Cyantraniliprole
  Minecto Pro	28, 6	Cyantraniliprole, Abamectin
  Rimon	15	Novaluron
  Cormoran	15,4A	Novaluron, Acetamiprid
  Movento	23	Spirotetramat

  Managing T. parvispinus will be challenging and will require an integrated approach to complement insecticide applications. The development of production practices reducing thrips populations and the use of natural enemies including predators and pathogens should be studied for integration with insecticide use. Biological control studies are ongoing and additional insecticide screenings in collaborations with stakeholders are being conducted for vegetable production.

  For more information on T. parvispinus related to ornamental production please visit UF/ IFAS MREC and TREC websites.

  Anna Mészáros¹, Julien M. Beuzelin², De-Fen Mou², and Craig J. Frey³

  ¹Palm Beach County Extension, University of Florida IFAS, West Palm Beach, FL
  ²Everglades Research and Education Center, University of Florida IFAS, Belle Glade, FL
  ³Hendry County Extension, University of Florida IFAS, LaBelle, FL

 

• Read: Risk Analysis of a Novel Bacterial Disease Management System

  Florida is the second largest pepper producer in the U.S., but production has decreased in the last 10 years. Bacterial spot on pepper can severely impact yields and increase production costs, thus threatening the long-term viability and profitability of the industry. Novel compounds utilizing biological control agents,  systemic acquired resistance induces, and biostimulants are among the newly developed products for sustainable and effective control of bacterial diseases in peppers. However, though many are proven effective, their adoption is  impeded due to the lack of information on the implementation costs. Researchers at UF-IFAS, Southwest Florida Research and Education Center studied the effect 11 different spray programs (Table 1) had on bell pepper yield and disease severity, in 2011. This analysis assesses the economic risks associated with each treatment in 2023 dollars. 

  We conduct partial budgeting and stochastic modeling to assess risks of adopting each treatment. Partial budgeting is used to reflect how each treatment affects the cost of production. The net benefit for each practice is calculated and compared to determine the economic feasibility of each treatment. Production costs come from updating the 2019-20 UF-IFAS budgets to 2023 dollars using inflation factors for fixed and variable costs. Monte Carlo simulations (1,000 draws) were used to randomize prices and yields and deviations in net returns are assessed to determine economic risks. Pepper prices come from USDA-NASS and are the basis for draws from the uniform distribution. Yields come from experiment station trials and the basis for draws from the triangular random distribution.

  Results showed that treatments whose average yield is at least 730 bu/acre provided positive net returns; these include spray programs 2, 3, 4, 5, and 7. Boxplots in Figure 1 show the means and deviations in net returns for the five spray programs we find to be viable in terms of average net returns and potential risk. On average, at $4,022/acre, spray program 2 provides the highest net returns and is the riskiest with standard deviation of $4,565/acre. At $2,614/acre, spray program 5 has average net returns that are comparable to program 7 and higher than programs 3 and 4, but with far less deviation in net returns (i.e., standard deviation is $3,043/acre). In essence, risk averse growers may prefer program 5 while risk takers may prefer program 2.

   

  Table 1. Spray program descriptions; weekly applications

  Program Num.	Product Description, Quantity/Acre
  1	Non-treated water control
  2	Manzate Pro Stik 75DG, 2.0 lb; Kocide 3000 DF, 2.0 lb
  3	NuCop 50HP, 1.0 lb; Manzate Pro Stik 75DG, 2.0 lb
  4	NuCop 50HP, 1.5 lb; Manzate Pro-Stik 75 DG, 2.0 lb
  5	NuCop 50HP, 2.0 lb; Manzate Pro-Stik, 2.0 lb
  6	Serenade Max WP, 1.0 lb; Kocide 3000 DF, 2.0 lb
  7	Serenade Max WP, 1.0 lb; Kocide 3000 DF, 2.0 lb; Manzate Pro-Stik, 2.0 lb
  8	Biological a*, 5.0 lb
  9	Biological b*, 1.25 lb
  10	Kocide 3000 DF, 0.75 lb; Actinovate AG, 3 oz
  11	Actigard 50 WG, 0.33 oz; Actinovate AG, 3 oz

  *Numbered compounds provided by the cooperator.

   

  Figure 1: Profitability Risk Analysis of Florida Spray Programs with Positive Net Returns 

  

  Tara Wade*¹², Lonege Ogisma¹, Kelvin Amon², and Pamela Roberts¹

  ¹University of Florida-IFAS Southwest Florida Research and Education Center

  ²Food and Resource Economics Department, University of Florida IFAS, Gainesville, FL

 

• Read: Best Management Practices: Updating UF/IFAS Fertilizer Recommendations

  Many UF/IFAS fertilizer and nutrient management recommendations for commercial production of field and forage crops are due for updates as production factors and practices have improved during the last three decades. To that end, the UF/IFAS Nutrient Management Program was recently established, with Dr. Tom Obreza as the Director, to administer the legislative intent of HB 5001, Specific Appropriation 1480A for nutrient management research and SB 1000 for site-specific nutrient management passed during the 2022 legislative session. More information on these bills can be found in the Nutrient Management Research article (4/26/2022) below. Current projects are being carried out on tomato, potato, snap bean, citrus, grain corn, watermelon, hemp, and peaches. Cotton, blueberry, lettuce, and sod production are being considered for addition next year.

  After hearing from stakeholders, the UF/IFAS BMP website (now entitled the UF/IFAS Plant Nutrient Research and Education Website, bmp.ifas.ufl.edu) is in reconstruction to create transparency, communicate project implementation details, convey real-time changes to UF/IFAS fertilizer recommendations, and provide a place for stakeholder feedback. The website describes how projects were selected, summarizes all projects initiated in response to 2022 legislative funding, and shows progress reports from each team. The site also contains a set of FAQs that address important BMP-related questions, including the process for updating recommendations, an explanation of the use of provisional recommendations, and the grower benefits of BMP implementation. Finally, the site contains information on the current fertilizer and nutrient management recommendations for studied crops, as well as links to recommendations for other crops, research summaries from which current recommendations are based, as well as multiple FDACS BMP manuals.

  UF/IFAS recommendations are also undergoing a format change to more clearly identify with the “4Rs” concept of nutrient management: right rate, right source, right timing, and right placement of fertilizers. But we are also adding the fifth “R”… right water management. Achieving efficient nutrient management goes far beyond the amount of fertilizer applied per acre. It involves the other 3 fertilizer “Rs” plus irrigation and drainage management. We are also looking to the future, beyond the 5Rs, to site-specific nutrient management. Many current projects involve site-specific aspects that will eventually allow growers, extension agents, and consultants to “fine-tune” nutrient management for specific sites based on field and crop characteristics, and perhaps even predicted weather patterns. Thanks to the Florida legislature’s investments, Florida’s nutrient management program is making great strides towards improving crop production and quality while minimizing nutrient losses to the environment.

 

• Read: Current and emerging diseases threatening sweet corn production in South Florida

  One of Dr. Xavier's research programs is focused on the development of management strategies for current and emerging diseases, including the ubiquitous northern corn leaf blight (NCLB) and the emergent tar spot disease of maize. Both diseases are challenging corn production in the United States, but science-based management strategies tailored for sweet corn in Florida are lacking.

  In 2022, the Foundation for Food & Agriculture Research (FFAR) awarded a Rapid Outcomes from Agricultural Research (ROAR) grant to Dr. Xavier and her collaborator, Dr. Resende (UF/IFAS Gainesville), to address the rapid spread of tar spot in sweet corn. This project aims to select sweet corn hybrids that are resistant to tar spot and identify effective chemical control programs. Additionally, the UF research team is examining the genetic diversity of the fungal pathogen causing this disease (i.e., Phyllachora maydis) and studying the epidemiological factors of tar spot development under South Florida conditions.

  Efforts to improve sweet corn production in Florida also include a comprehensive understanding of the NCLB pathosystem and the development of a breeding program for NCLB resistance. Dr. Xavier and Dr. Resende's ongoing research can also impact sweet corn growers and markets throughout the United States. Such efforts will bolster the progression of management protocols for current and emerging sweet corn diseases. Additional information from the UF/IFAS Sweet Corn Breeding Lab can be found here: UF | Resende Lab - Sweet Corn Breeding.

  Acknowledgments:
  The sweet corn tar spot project is supported by a FFAR-ROAR grant ID 22-000443.

 

• Read: Monitoring Insect Vectors and Emerging Diseases in South Florida

  Did you know that plants also get sick? Plant virus infection can induce disease symptoms that reduce crop value such as necrosis, discoloration, lesions, and affect crops’ normal growth and development. More importantly, virus infection can cause plant death and hence cause huge economic loss to crop growers. Many plant viruses are transmitted by insects. These “insect vectors” use their needle-like mouthpart structure, called “stylet”, for piercing plant tissue and sucking plant sap, and the virus transmission happens when they feed on plants.

  The research of Dr. Mou of the UF/IFAS Everglades Research and Education Center (EREC) focuses on identifying which insect species is responsible for plant pathogen transmission and studying the transmission mechanisms. Based on this research, her goal is to develop management tools to target the vector species and control virus diseases. The first phase of her program is to initiate a monitoring program for insect vectors and emerging diseases of important crops at the Everglades Agricultural Area.

  Recently, a thrips-transmitted virus disease of lettuce caused by Impatiens necrotic spot viruses (INSV) severely impacted lettuce production in California. Dr. Mou is plan to monitor thrips population levels in Florida lettuce farms and screen the thrips for INSV to make sure Florida lettuce is not affected by the virus. Additionally, in collaboration with Dr. Germán Sandoya who leads the lettuce breeding program at the UF/IFAS EREC, Dr. Mou will examine lettuce resistance to the thrips. Ultimately, Dr. Mou will merge insect ecology, molecular biology, and vector entomology to develop measures that prevent the outbreak of the INSV in Florida lettuce.

• Read: Crunching the Numbers for Tomato using AgTools technology

  Economic risk is the possibility of adversity or loss and refers to “uncertainty that matters.” In agriculture, risks include production, financial, human resource, marketing, and legal and/or regulatory risk. Risk management involves choosing among available alternatives to reduce the effects of risk. Managing uncertainty requires evaluation of tradeoffs between choices, changes across and within areas of risk, knowledge of expected returns, degree of desired entrepreneurial freedom, and other measurable factors. Optimal decision-making occurs where the marginal gains meet or exceed marginal costs of each choice and drives an individual producer’s ability to compete in the markets.

  Given that market access and market share drive profitability, exciting new technologies are emerging that reduce the cost of KNOWING and empower the individuals making more informed decisions. Built by a family of farmers, AgTools developed algorithms to calculate a billion transactions per second, helping farmers and commodity buyers understand how scores of factors can affect their contracts for the produce supply chain. A subscription-based service specific to each fruit or vegetable and informed by experienced producers and retail buyers, the AgTools engineers find and organize current and historical secondary data. Commodity data with over 76 variables and 29 years of records such as market demands, labor trends, transportation costs, and more, are capturing data used by growers to make daily production and harvest decisions at the margin. Some of these variables include market price data, import data and trends, fuel and labor costs over time, current and optimal weather, measures of sustainability (food miles), up to the minute news specific to commodity, and a brand-new feature allowing buyers to see real-time growth stages of each crop and any reported disease issues unique to the production region.

  Below are demonstrations of why this technology offers time-saving ways to improve marketing decisions using the AgTools up-to-the-minute shipping point price and volume trends for the 2022-23 tomato season (1 Oct 2022 through 3 February 2023):

  Please contact Dr. Morgan to request additional information about AgTools and/or request a market analysis. She maintains AgTools subscriptions for tomato, tomato (plum-type), blueberries, oranges, peppers (bell-type), peppers (other), romaine lettuce, spinach, strawberries, watermelons, watermelons (seeded), and watermelons (seedless).

• Read: Bacterial Diseases on Pepper

  In 2019, a USDA-SCRI grant was funded to investigate bacterial diseases that occur on pepper. The grant members are comprised of research and extension faculty at UF, five other universities, and USDA, from the disciplines of plant pathology, plant breeding, and economics. The overarching goal of this project is ‘to reduce economic losses in pepper production caused by foliar bacterial pathogens and develop strategies to minimize losses from bacterial diseases on pepper’. The team members are identifying and characterizing the bacteria occurring on all types of pepper and developing detection assays, breeding for resistance, evaluating new materials for management, and evaluating the economics associated with management practices.

  Studies from this project include characterizing the current population of the bacterial spot pathogen caused by Xanthomonas species from field surveys initiated in southwest Florida. More than 500 strains of bacteria were isolated from peppers, including leaves and fruit, with symptoms typical of bacterial spot. Samples were collected from a wide variety of peppers including bell, mini sweets, Cubanelle, jalapenos, and other specialty-type peppers beginning in 2019. Strains were then characterized for pathogenicity, race, sensitivity to copper, and sensitivity to an antibiotic. From this sampling, most of the bacteria were Xanthomonas euvesicatoria and were mainly races 1, 3, and 6 with four other races detected infrequently. Approximately two-thirds of samples were copper tolerant and only a few of them showed antibiotic resistance.

  This most recent population study of pepper bacterial diseases in south Florida offers insights into management. Using resistant varieties to the main races detected should be the first management strategy employed. Additionally, results indicate potential effectiveness of copper and antibiotic management for bacterial spot. For further assistance in developing a bacterial spot management plan, contact your local extension agent and/or the UF Plant Pathology team.

  Acknowledgements:

  Aastha Subedi, Graduate Research Assistant, Plant Pathology Department. Jeff Jones, Distinguished Professor, Plant Pathology Department. Erica Goss, Associate Professor, Plant Pathology Department and Emerging Pathogens Institute. University of Florida.

  This work is supported by the United States Department of Agriculture Specialty Crops Research Initiative project [grant no. 2019-51181-30010/project accession no. 1020301] from the USDA National Institute of Food and Agriculture.

• Read: Studying fumigation impacts on soil microbes to improve production

    Fumigation has been a standard practice for vegetable production for over 50 years and can be an effective method to control some soilborne plant pathogens. However, the efficacy of fumigants can vary and it’s not clear how fumigants impact the other microbes in the soil (i.e. the non-target microbes). Many soil microbes (bacteria and fungi) can be beneficial for plant growth, so understanding if these beneficial microbes are still in the soil after fumigation, and how long it takes for them to return to the soil, could help optimize or improve fumigation practices.

    Dr. Sarah Strauss was awarded a grant from USDA-NIFA to address these questions for fumigants commonly used in Florida tomato and strawberry production. In addition, the project will examine how changes in non-target soil microbes might impact the suppression of soilborne plant pathogens, nutrient availability, and weed growth. Weed scientist Dr. Nathan Boyd, plant pathologist Dr. Gary Vallad, and soil scientist Dr. Mary Lusk are joining her on the project to help address these questions.

    The first phase of the project is focused on tomato field trials being conducted at the UF/IFAS Gulf Coast Research and Education Center (GCREC), where soil microbes and pathogen abundances are being assessed at frequent intervals after fumigation and throughout the production cycle. Fumigants being assessed include Telone C35, Pic-Clor 60, Pic100, K-pam, Pic-Clor 60 + K-pam, and a no treatment control. The next phase of the project will involve working with Florida strawberry and tomato growers to collect samples in commercial fields.

    Interested in learning more about fumigant impacts on soil microbes or participating in our trials? Contact Dr. Strauss and Craig Frey for more information.

• Read: Effective, Economical, and Eco-friendly Weed Management in Vegetable Production

     Weed management is fundamental to successfully growing vegetables in Florida using a plasticulture system. The phase-out of methyl bromide has resulted in a lack of broad-spectrum activity and consistency in weed suppression. A multi-strategy approach is now needed. 

     Enhancing the utility of alternative herbicides is a primary focus of Dr. Kanissery's program. Due to his research results, Dr. Kanissery recommends applying pre-emergent or residual herbicides in tandem with a pre-mulching soil fumigation strategy. This system is effective because the pre-emergent herbicides will typically be 'activated' by the condensation under the mulch. Herbicides applied this way also better manage weeds on bed edges than fumigants injected through the drip irrigation due to the limited lateral movement of current fumigants. A recent study from Dr. Kanissery's team compared the use of pre-emergence herbicides under plastic to the use of plastic alone. Results illustrated that after using a pre-emergence herbicide transplanted bell pepper had significantly lower weed competition and double the yield.

     Despite these benefits, there has been relatively little research, development, or registration of herbicides for use under plastic mulches, making herbicide choices severely limited in raised bed vegetable production. Dr. Kanissery and his fellow UF/IFAS Weed Scientist collaborators, Dr. Nathan Boyd and Dr. Peter Dittmar, aim to make available chemistries as effective as possible by fine-tuning the practices for successfully incorporating herbicides into beds before laying out the plastic mulch in order to enhance efficacy and crop safety.

     Dr. Kanissery and his team also provide a statewide service for weed identification and diagnosis of herbicide phytotoxicity in conjunction with the Plant Disease Diagnostic Clinic at Southwest Florida REC. If you have questions about your weeds or using herbicides to manage them, we’ed like to help. Please get in touch with Dr. Kanissery for more information.

• Read: Identification and Characterization of a New Tomato Virus in Florida

     Did you know there are currently more than 130 known plant virus species that infect tomato plants? UF/IFAS Plant Pathologist Ozgur Batuman and his team have been on the hunt for a new ilarvirus infecting tomato.

     Ilarviruses have long been known to infect tomatoes. Tobacco streak virus (TSV) is the first ilarvirus identified in tomatoes and distributed globally. Since 1985, several other ilarviruses have been detected in tomatoes in several European countries and in California, USA. In 2015, a novel virus emergence causing necrotic streak disease was reported in tomato plants in Miami-Dade and Palm Beach counties. Later, the virus was characterized as a new ilarvirus named tomato necrotic streak virus (TomNSV).

     In 2020, Dr. Batuman’s team collected hundreds of tomato plant samples during field surveys for virus and virus-like diseases in main tomato production regions throughout Florida. These tomatoes showed virus-like disease symptoms, including stunting, leaf deformation, and necrosis on leaves, stems, and fruits. The symptomatic samples were analyzed to identify potential causal agent(s), and initial results suggested that some of the samples had a new ilarvirus species that was not previously known to infect tomato plants or cause disease in Florida fields.

     Although the threat of this new ilarvirus to Florida tomatoes is unknown, field observations suggest that it may not pose a significant economic concern. However, ilarviruses are pollen transmitted by thrips feeding on tomatoes. Thus, growers must keep thrips populations (and inoculum sources, i.e., weeds) under control, particularly during the vegetative growth stages of plants early in the season.

     New disease outbreaks in tomato production in Florida have the potential to cause millions of dollars in losses to the industry, and rapid detection of the putative new virus is the key to preventing disease establishment and further spread. Recent funding from an FDACS-SCBGP grant will address essential knowledge gaps about this new virus’s biology and epidemiology that will allow Dr. Batuman’s team to develop detection methods and implement rapid eradication and prevention actions against possible disease outbreaks in Florida.

     If you suspect ilarvirus-like symptoms in your field, please contact Ozgur Batuman or Craig Frey to schedule a field visit.

• Read: Listronotus sp., an Emerging Weevil Pest of Celery and Parsley in Southern Florida

  Anna Mészáros of the UF/IFAS Palm Beach County Extension office and Dr. Julien Beuzelin of the UF/IFAS Everglades Research and Education Center conduct research into the increase in unusual insect injury observed since 2020 in organic and conventional celery and parsley fields in southern Florida. This injury consisted of weevil larval tunneling through plant petioles, crowns, and roots. A research and extension program was initiated to identify the insect causing the injury, study pest population dynamics, evaluate insecticide efficacy, and promote information exchange to answer grower needs.

  • The weevil adults infesting celery plants were identified as Listronotus sparsus, a relatively widespread species that had not been reported as a crop pest.
  • This weevil exhibits behavior comparable to carrot weevils, oregonensis and L. texanus, which are serious pests of Apiaceae crops in the Great Lakes region and Texas, respectively. Thus, this weevil might represent a significant threat to celery, parsley, dill, cilantro, and carrot production in Florida.
  • In celery, most of the weevil damage is at the base of the petioles, especially in the outer petioles; tunnels can be as long as four inches from the base of the plant going up through the petiole. Weevils can also feed on the crowns of celery plants. In parsley plants the petioles are thinner than in celery plants, therefore weevils tend to feed more on the base of the plant and the roots.
  • Observations suggest that the weevil infests plants throughout the crop season and has multiple overlapping generations per year.
  • Based on grower commercial practices and our experiments, Vydate is currently recommended for weevil management in celery, however, this insecticide is not registered for use in parsley. Exirel and Diamond might have activity against the weevil, however, whereas Exirel is registered for use on celery and parsley, Diamond is not registered on either crop. Thus, there is a need for additional studies evaluating insecticides, including Exirel and Diamond, which showed promising results in Canada for oregonensis control. These studies might lead to new insecticide registrations and updated L. sparsus management recommendations.

   

  We are thankful for our great collaborations with Florida celery and parsley growers and crop consultants who have shared their knowledge and have assisted with on-farm experiments to develop a management solution for L. sparsus.

  If you suspect a L. sparsus infestation in your field, please contact Julien Beuzelin, jbeuzelin@ufl.edu or Anna Meszaros, ameszaros@ufl.edu.

  For more information on L. sparsus, including details on feeding symptoms and management research, visit this page.

• Read: Expansion of the Florida Soil Moisture Sensor Network

        Dr. Vivek Sharma leads the Florida statewide soil moisture sensor (SMS) network. The network began as a project in the Suwannee Valley in 2018. The premise of the project was to lend free sensors to agents and producers to increase the adoption of irrigation best management practices throughout the region. The network has grown from 20 SMS and a handful of extension agents in North Florida in 2018, to over 80 SMS and more than 10 agents across the state today.
  
        The project seeks to use the most appropriate, cost-effective, and advanced technology to enable growers to make informed decisions regarding irrigation management. The goal is to get SMS into the hands of growers to enable them to experience the benefits of SMS without requiring them to make the significant capital investment. There continues to be a very high adoption rate, as growers clearly see the return on investment of SMS as they adjust irrigation practices to conserve water and enhance crop water and nutrient use efficiency. Water quality is also improved through the reduction of runoff and leaching events.
  
        Are you a grower interested in testing out a SMS for the season? If so, you may contact any of the agents involved in the program listed here:

  
  Hendry, Glades, Charlotte, Lee, and Collier Counties
  Craig Frey, Multi-County Commercial Vegetable Agent

  Palm Beach County
  Anna Mészáros, Commercial Vegetable Agent

  Hillsborough County
  Wael Elwakil, Commercial Fruit and Vegetable Agent

  Manatee County
  Lisa Hickey, Sustainable Food Systems Agent
  
  Martin County
  Yvette Goodiel, Sustainability & Commercial Horticulture Agent
  
  Flagler and Putnam Counties
  Wendy Mussoline, Multi-County Agriculture Agent
  
  Levy County
  Mark Warren, Row Crops and Commercial Agriculture Agent
  
  DeSoto, Hardee, and Manatee Counties
  Ajia Paolillo, Multi-County Citrus Agent
  
  Hillsborough and Polk Counties
  Shawn Steed, Commercial Horticulture Agent
  
  Marion County
  Gabriel Vicari, Water Resources Agent

• Read: Nutrient Management Research

  The FY 22-23 state budget includes a line item showing $8,763,753 in nonrecurring funds for UF/IFAS to support specific soil fertility and nutrient management research. The exact language describing the legislative intent for the funding is:

  • “To conduct a study designed to examine the appropriate rate for applying fertilizer on tomatoes, potatoes, citrus, corn, green beans, and any other crop identified by UF/IFAS as needing further research for normal and economical crop production.”
  • “The study shall include recommendations on best management practices (BMPs) for supplying fertilizer to the crop to achieve maximum yield and quality goals of the grower while doing so in a manner that minimizes nutrient inefficiencies to the environment.”

  In addition, the legislature recently passed SB 1000, which contains this directive for UF/IFAS:

  • “The University of Florida, Institute of Food and Agricultural Sciences shall analyze the use of site-specific nutrient management for crops other than citrus and crop rotations and shall develop a research plan and interim recommendations for implementation of site-specific nutrient management.”

  Dedicated state funding of this magnitude for fertilizer/nutrient management work is unprecedented. Dr. Shukla and Dr. Agehara and their teams have been working hard to carry out this work in tomato and potato during its inaugural season in South and Central Florida, along with Dr. Christian Christiansen and Dr. Lincoln Zotarelli in the Hastings area. For the upcoming 2022-2023 production season, multiple teams from around the state will be expanding this research.
  
  It is critical that the grower community engages in this research as well. Participation is necessary so that these studies may appropriately reflect conditions in commercial farms (to better assess rate responses), and accurately measure variables across farms that may impact nutrient availability and crop yield (to evaluate the need for site-specific nutrient management). Contact us for more information.

• Read: Integrated Pest and Disease Management in Vegetable Crops

        The southern root-knot nematode (Meloidogyne incognita) is a major pest of tomato, cucumber, and squash, causing severe declines in crop yield and quality in Florida and around the world. Dr. Zhang utilizes his global connections to broaden his scope in evaluating novel non-fumigant control measures against this pest to hasten the development of new technologies that provide growers with a larger toolbox.

        Fluopimomide is a new fungicide that was developed by Shandong Sino-Agri Union Biotechnology Co. Ltd. It was derived from fluopicolide, which can control diseases caused by oomycete pathogens, yet it has been found to have a broader spectrum of antimicrobial activities due to its multiple modes of action. Due to these multiple modes of action, the mechanism of action that enables its function as a nematicide is not yet understood. Another study of Dr. Zhang’s, conducted in China, investigated the integrated management of the southern root-knot nematode and Fusarium oxysporum in cucumber and found that the combined application of abamectin and fludioxonil improved cucumber yields. In Homestead, FL, Dr. Zhang’s team conducted a recent study that evaluated the use of fluazaindolizine for management of southern root-knot nematode in squash grown in calcareous soils. Results indicated a reduction in southern root-knot nematode population and increase in crop yield comparable to oxamyl (Vidate).

        Dr. Zhang’s work to evaluate the integrated use of new disease management tools is essential for the Florida vegetable industry and continues to provide growers with insight on how to integrate these tools into their production systems effectively.

• Read: Diamide Insecticide Resistance in Diamondback Moth

        Diamondback moth (DBM) is a major pest of cruciferous crops with global annual damage estimates ranging from US $4-5 billion. Multiple mechanisms of insecticide resistance have been discovered in DBM, from avoidance behaviors to metabolism of insecticidal compounds, resulting in at least 95 different insecticides that have been documented to fail to control DBM.
  
        Diamides are a relatively new insecticide, with chlorantraniliprole (Coragen) and cyantraniliprole (Exirel) being released in 2008 and 2012, respectively.  DBM resistance occurred quickly in numerous populations worldwide, including in several sites in Florida and Georgia.

  

        Dr. Smith’s multi-state team found that 90% of a DBM population from Manatee County, FL, had genes associated with resistance to chlorantraniliprole with an LC50 that was 2,845 times the susceptible control. Results indicated that the population also had resistance to cyantraniliprole, with an LC50 that was 108 times the susceptible control.

        The team intends to extend this study to determine the prevalence of the identified gene mutation and the corresponding level of resistance to chlorantraniliprole and cyantraniliprole. The expectation is that such field studies will open the possibility of using a molecular diagnostic approach to anticipate control success/failure before insecticide application.

        It should be noted that this recently published study was from resistant populations collected in 2018, and may not represent current field populations. The full paper can be found here: A Target Site Mutation Associated With Diamide Insecticide Resistance in the Diamondback Moth is Widespread in South Georgia and Florida Populations. More extensive DBM insecticide resistance screening by Dr. Smith’s team from 2016 to 2019 can be found here: Regional Survey of Diamondback Moth Response to Maximum Dosages of Insecticides in Georgia and Florida.

        Sampling is currently underway to further assess DBM resistance in populations around the state.

• Read: Low-Cost, Smart Technology for Input Management Utilizing AI

        A recent economic analysis estimated that agrochemicals total $1660 per acre in Southwest Florida tomato production, or about 20% of total preharvest costs (Wade et al., 2020). Precision spray technology has the potential to reduce these inputs while maintaining efficacy. This would increase grower profitability while decreasing environmental impacts and the risk of pesticide resistance.
  
        Agrochemicals are typically applied using hydraulic and hydro-pneumatic sprayers. These have high inefficiencies and result in significant amounts of off-target active ingredients. Dr. Ampatzidis and his team are seeking low-cost, smart technology systems to achieve grower efficacy standards while reducing inefficiencies and, therefore, grower costs.
  
        One such system that Dr. Ampatzidis’s lab recently developed and evaluated was a preliminary prototype of a low-cost, smart herbicide sprayer. For under $1,500, the sprayer used an AI-based machine vision software to distinguish between target weeds and the crop, and had hardware with 12 individual fast response nozzles for spraying. Their work analyzed multiple low-cost processing systems and the best demonstrated the ability to detect 100% of target weeds and accurately spray 91-95% of the target weeds in artificial situations over multiple trials. In field situations, target weed detection was reduced to 85% while spray precision was reduced to 71%. A second prototype is now underway to distinguish between the crop and different types of weeds (grass and broadleaf) as well as to improve detection and spray accuracy in field situations.
  
        Additionally, Dr. Ampatzidis and his team have recently developed a low-cost, smart tree-crop sprayer. This sprayer uses AI to detect citrus trees and determine their height, leaf density, and fruit count and varies the amount of insecticide sprayed for each tree based on this data. It is estimated that this increase in application efficiency will reduce chemical use by about 30% compared to traditional spray methods. This technology has the potential to be adapted to vegetable production systems as well, with the low-cost system saving growers input costs while reducing environmental impacts.
  
        Interested in working with the robotics and AI team to develop a project for your production system? Contact Dr. Ampatzidis and Craig Frey for more information.

• Read: Brown Marmorated Stink Bugs (BMSB) in Florida Tomatoes

         Stink bugs have increasingly become a major pest in tomato production on the east coast of the United States. For much of the region, this is due to the large populations of an invasive species, the Brown Marmorated Stink Bug (BMSB), Halyomorpha halys (Stål), in combination with the phase-out of broad-spectrum insecticides. In Florida, however, large population outbreaks of BMSB have yet to be observed.       

         There are two stink bug species that are major pests in Florida tomato crops, the southern green stink bug, Nezara viridula (Linnaeus), and the brown stink bug, Euschistus servus (Say). The leaf footed bug, Leptoglossus phyllopus (Linnaeus), is also known to cause significant damage in some portions of the state, while the green stink bug, Chinavia halaris (Say), is considered a minor pest of tomato. Over the last few seasons, stink bug damage in Florida tomato has become concerning, and while the phase-out of broad-spectrum insecticides likely plays a role, that has been occurring over a much longer period of time and does not explain the spike in damage recently seen.       

         Last year, a regional survey effort was established with support from the Florida Tomato Committee and multiple growers. Dr. Amanda Hodges led this surveying effort in partnership with Craig Frey, the Southwest Florida Vegetable Extension Agent. The goal was to understand the species mix and population levels at multiple locations throughout the spring growing season. BMSB was identified in field populations for the first time in Manatee, Hendry, and Lee Counties. Previously in Florida, it was only known that a localized population existed in Lake County. Additionally, results indicated a large species mix across all locations.       

         This species-mix data was obtained using yellow pyramid traps, however, the traps did not function well to capture population levels and yielded data inconsistent with population dynamics. The regional scouting effort will continue this spring with the deployment of blacklight traps, which have shown to provide reliable information in the Mid-Atlantic region. If blacklight traps prove successful in representing the population dynamics of Florida stink bug species, future years of monitoring around the state will provide growers with real-time information of population peaks and, hopefully, management thresholds. Future updates will be provided as the research effort progresses.

• Read: The Distribution and Management of Meloidogyne enterolobii

         Meloidogyne enterolobii (M.e.), or Guava Root Knot Nematode (GRKN), is a highly virulent root-knot nematode (RKN) species. In addition to the potential to cause significant crop loss, M.e. may also jeopardize access to export markets for many root crops. It is considered one of the most damaging RKN species due to its ability to cause severe galling symptoms, infect many plant species, and overcome resistance in current varieties that are effective against other RKN species. Once M.e. is present it is difficult to manage, and current recommendations suggest rotating with non-hosts for 3 years. 
  
         Dr. Johan Desaeger is part of a regional team to survey and study M.e., along with UF/IFAS Nematologist Dr. Zane Grabau and Agricultural Economist Dr. Zhengfei Guan.
  
  Objectives:
   
  -  Study the prevalence and distribution of M.e. in vegetable crops in the Southeast and characterize the genetic variability encountered 
  
  -  Evaluate and develop vegetable germplasm with resistance to M.e. 
  
  -  Evaluate the efficacy of nematicides, cover crops, and crop rotation as management strategies for M.e. 
  
  -  Assess the costs and returns of management tactics on sweet potato, cucumber, watermelon, and tomato 
  
         If you have planted root-knot nematode resistant varieties and are still observing galling in your roots, you may have M.e.. Contact Dr. Desaeger or your local extension agent to ask for a species identification so that a monitoring and management program may be developed for you. If you want to know more about M.e. and this multistate research project, visit findmenematode.org.

• Read: Kaolin and Limonene for Whitefly Control in Vegetable Crops

        Due to the development of insecticide resistance and difficulties in managing B. tabaci with conventional insecticides, significant agricultural research has been aimed at finding alternative control methods or developing techniques that enhance existing methods. Dr. Martini is investigating the utilization of Kaolin clay (sell under the name Surround®) and limonene (an essential oil) to keep whiteflies out of susceptible crops. Kaolin acts as a contact repellent, whereas limonene repels whiteflies from distance.

  

        Initial trials conducted at the North Florida Research and Education Center in the fall of 2019 showed that, individually, Kaolin and limonene slightly reduced whitefly populations on tomato. More significantly, they demonstrated an additive effect when applying both Kaolin and limonene (Figure 2). The efficacity of Kaolin in addition to limonene was particularly high during dry condition, and was reduced after rainfall.

  

        Subsequently, an on-farm trial was conducted in fall 2021 with treatments that included the grower’s weekly insecticide program, the grower’s weekly insecticide program with weekly applications of Kaolin + limonene, and only Kaolin + limonene applications. Results demonstrated reduced whitefly counts with Kaolin in addition to limonene. Alternating the grower’s weekly insecticide program with weekly applications of Kaolin + limonene reduced B. tabaci populations the most. (Figure 3).

  

        While Kaolin and limonene will not replace the use of insecticides, this data suggests that a weekly alternating treatment can be used effectively by conventional and organic growers as part of an integrated whitefly management program. Additional recommendations include eliminating weeds in the field that may act as secondary hosts for B. tabaci during the off-season, and using UV-reflective, plastic bedding to disrupt B. tabaci’s host searching capacity.

  In this study, Surround was used at half the industrial rate (¼ lbs. per gallon of water or 113g/gal), and limonene was used at 0.5% (19 mL per gallon of water). Kaolin and limonene were mixed directly in the sprayer tank. To avoid clogging of spraying material with Kaolin, it is important to use a sprayer machine with high horsepower equipped with an agitator.

• Read: Update on Cucurbit Downy Mildew Management

        Cucurbit production in Florida is impacted by downy mildew on a yearly basis. The nearly continuous production of cucurbits in Florida puts extensive selection pressure on the pathogen population for resistance to the current labeled fungicides and loss of efficacy is becoming a major concern for Florida cucurbit growers. Recently published research by Gary Vallad’s team compared the efficacy of 11 different insecticides across 3 trials.

  

        Results indicate that there are multiple active ingredients are effective against CDM, but none that exist as a silver bullet. Dimethomorph, fluopicolide, and cymoxanil were much less effective than the other active ingredients, and these results confirm reports from other states. Interestingly, infrequent application of some insecticides with low efficacy (such as chlorothalonil), were comparable to weekly appilcations of more effective active ingredients. Results also indicate that application frequency of the most effective materials (ethaboxam, fluazinam, oxathiapripolin, and cyazofamid) may be reduced in seasons less conducive for CDM development, as the effectiveness of weekly applications was not significantly greater than bi-weekly applications. From this data, the duration of field activity was also determined:

  

        Given the aggressive nature of CDM, this is not a recommendation for growers to adopt a 14-day interval with these fungicides, but rather to leverage this information to improve their rotations and minimize reliance on cyazofamid or oxathiapiprolin, especially when environmental conditions are not favorable for rapid disease development. Increasing rotations will limit fungicide resistance in Florida and assure a larger toolbox for years to come.

        Shirley, A., G.E. Vallad, N.S. Dufault, R. Raid, and L. Quesada-Ocampo. 2021. Duration of downy mildew control achieved with fungicides on cucumber under Florida field conditions. Plant Disease First Look: https://doi.org/10.1094/PDIS-03-21-0507-RE.

• Read: Asian Bean Thrips Research Continues

        Surveying of Asian bean thrips occurred throughout the summer in select locations, and results indicated that populations of ABT decreased dramatically a few weeks after bean crops were terminated. Locations of interest included hot spots from the previous growing season and sunn hemp fields, which is suspected to be an important host. Blue sticky cards were collected on a weekly basis and there were 9 ABT were identified from 36 traps between 6/16/2021 and 9/1/2021. Results indicate populations did not increase through the summer on potential hosts, as previously feared, but also demonstrated ABT are in the Hendry County area year-round.

        Preliminary insecticide efficacy results from Dr. Hugh Smith and Dr. Bruno Rossitto De Marchi are highlighted below. In summary, these experiments demonstrated methomyl (Lannate), spinetoram (Radiant), acetamiprid (Assail), and cyantraniliprole (Exirel) were most effective against adults under laboratory conditions. Abamectin (Agri-Mek) also showed effectiveness, although was only included with a few bioassays. Pyrethroids were not effective and are not recommended for management of Asian bean thrips. There was greater variation in the larval study, with spirotetramat (Movento) and novaluron (Rimon) causing the most significant mortality.
  
  
  

  

  

  

  2021-2022 Monitoring of Asian Bean Thrips

        Monitoring Asian bean thrips in snap beans will continue for the 2021-2022 growing season, with weekly reports compiled by Craig Frey, Anna Mészáros, and collaborating partners. Anna was previously part of the team at Glades Crop Care, Inc. that first identified Asian bean thrips, and she has now joined UF/IFAS Extension in Palm Beach County. We hope to expand the number of locations being scouted this season, particularly in Palm Beach County and north of the 2020-2021 monitoring area. Please contact Craig or Anna if you are interested in partnering with us as a grower, in which we will scout your fields, or as a scout, in which you will contribute generalized data on a regional (not farm specific) scale. 

  Craig Frey Commercial Veg Extension Agent - Southwest Florida	Anna Mészáros Commercial Veg Extension Agent - Palm Beach County
  (863) 674-4092 craigfrey@ufl.edu	(561) 233-1759 ameszaros@ufl.edu

• Read: Sulfur Amendments to Lower pH in Southwest Florida

  Preliminary Results

        The granular S experiment lasted for eight weeks with no change in soil pH for any of the rates tested.

  

        The water-dispersible S applied treatments were conducted in two 4-week intervals. Drastic pH reductions were observed in both four-week tests in all treatments, however, it was most significant in the higher rates.

  

  

  Click here for the full report