Source: UNIVERSITY OF GEORGIA submitted to NRP
SAM: SUSTAINABLE ANTHRACNOSE MANAGEMENT FOR WATERMELON AND CUCUMBER GROWERS IN THE EASTERN U.S.
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
ACTIVE
Funding Source
OTHER GRANTS
Reporting Frequency
Annual
Accession No.
1031447
Grant No.
2023-51181-41156
Cumulative Award Amt.
$4,790,065.00
Proposal No.
2023-05661
Multistate No.
(N/A)
Project Start Date
Sep 1, 2023
Project End Date
Aug 31, 2027
Grant Year
2023
Program Code
[SCRI]- Specialty Crop Research Initiative
Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
(N/A)
Non Technical Summary
Anthracnose in watermelon and cucumber can severely impact yields and increase production costs in the absence of effective control options and is a threat to the long-term viability and profitability of the U.S. cucurbit industry. A coordinated, multi-state effort is required to improve our understanding of the recent anthracnose outbreaks by determining pathogen biology, population structure, host specificity, and fungicide resistance profiles of Colletotrichum spp. causing severe anthracnose outbreaks in cucurbit crops. This knowledge will lead to improved management strategies. Assessing the effects of specific production practices, environmental conditions, and inoculum on disease outbreaks can aid the development of practical, economically viable, and environmentally-sound strategies to limit yield losses due to anthracnose. Our team will address the pathogens (leverage genomics and population biology to identify theColletotrichumspecies complex(es) and inoculum sources), the host (screen commercial varieties and PI lines), and the environment (production practices) that constitute the disease triangle. We will integrate economic assessments and Extension efforts into each objective to further strengthen our project. This project meets the legislatively mandated SCRI focus areas of "efforts to identify and address threats from pests and diseases" and "efforts to improve production efficiency, handling and processing, productivity, and profitability."
Animal Health Component
60%
Research Effort Categories
Basic
40%
Applied
60%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
21614201102100%
Knowledge Area
216 - Integrated Pest Management Systems;

Subject Of Investigation
1420 - Melons;

Field Of Science
1102 - Mycology;
Goals / Objectives
Objective 1: Understand the pathogen population biology of emerging anthracnose epidemics of cucurbit crops in the eastern U.S. to improve management strategies. We will leverage genomics and population biology to identify the Colletotrichum species complex(es) involved in emerging watermelon and cucumber anthracnose epidemics in the eastern U.S.; determine the population genetic structure, host specificity, and fungicide resistance profile(s) of species involved; and develop PCR-based diagnostic tools for Colletotrichum species identification and detection of fungicide resistance against fungicide groups (QoI, MBC, DMI and SDHI) (45%).Objective 2: Identify effective production and management practices to prevent or reduce cucurbit anthracnose. We will examine how different sources of inoculum (seed and crop debris), production practices (e.g., including drip vs. overhead irrigation), fungicide programs, host response in varietal selections and core PI collections of watermelon and cucumber lines contribute to cucurbit anthracnose outbreaks; and develop pre- and post-harvest management programs that are environmentally and economically viable (55%).
Project Methods
Objective 1: Using standardized survey and isolation protocols, watermelon, cucumber, and other cucurbit crops (squash, cantaloupe) will be surveyed for anthracnose symptoms in seven eastern U.S. states representing more than 50% and 40% of the national watermelon and cucumber production, respectively (8-10 fields/state surveyed 2-3 times/season). Isolates collected will be used for the population biology and comparative genomics stuies. We will study pathogen species diversity using multilocus sequencing and pathogen population genetic structure and diversity using whole genome sequencing, single nucleotide polymorphism calling, and standard population genetic analyses. Host specificity and race-typing will be determined using a panel of cucurbit genotypes (watermelon, cucumber, squash, cantaloupe) in greenhouse bioassays. Resistance to QoI fungicides and development of molecular diagnostic assays for resistance and species identification will be determined using standard methods for plant-pathogenic fungi. Understanding the diversity and prevalence of Colletotrichum spp. as well as the QoI fungicide resistance profile in these regions will aid in development of practical methods, not only to detect Colletotrichum spp. but also to screen for QoI resistance within different populations.Objective 2: We will examine how seed-borne inoculum and production practices, including drip vs. overhead irrigation, fungicide programs, host response in varietal selections and core PI collection of watermelon and cucumber lines, and seed treatments, contribute toColletotrichumspp. outbreaks of cucurbit anthracnose and develop pre- and post-harvest management programs that are environmentally and economically viable. We will coordinate among seven eastern U.S. states (FL, GA, SC, NC, VA, DE and NY) and evaluate how production practices impact cucurbit anthracnose outbreaks: irrigation (type), selection of commercial cultivars (watermelon and cucumber) and fungicide programs. We will also coordinate with the CucCAP2 (SCRI PROPOSAL NO: 2020-51181-32139) group. This group has identified a panel of watermelon and cucumber breeding lines that are suitable for productivity and profitability; however, these lines have not been screened for cucurbit anthracnose. This project will provide an opportunity to screen these breeding lines along with other commercial cultivars, and the results will benefit both projects. The impact of cucurbit anthracnose on fruit yield, quality and marketability will be evaluated in replicated trial plots in FL, GA, SC, NC, VA, DE and NY. We will assess if debris and seeds play a role in anthracnose outbreaks in replicated field trials in watermelon and cucumber. We will further assess different crop debris management practices and seed treatments to reduce pathogen survival. We will conduct economic and stakeholder advisory panel assessments of regional trials each year that will enable us to determine the cost-benefit trade-off of recommended management strategies. Economic surveys through stakeholder engagement will be conducted to estimate the economic impact of cucurbit anthracnose on watermelon and cucumber growers. Standard extension platforms that will integrate feedback from the stakeholders will be used to disseminate outcomes of this project, which will ensure the highest likelihood of adoption.

Progress 09/01/24 to 08/31/25

Outputs
Target Audience:Primary audience of the project is the cucurbit producers in the eastern US. This includes cucurbit producers, packers, shippers, agronomists, crop consultants, farm managers, field workers, seed companies, and dealers; and cucurbit storage and shipping/transport personnel and companies. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Six graduate studnets, five post-doctoral reseasrch associates, 4 research professionals and technicians, and undergraduate students are currently involved in this project and have been trained on different aspects of the project. These opportunities include conducting thesis or dissertation research, participating in computational, laboratory, greenhouse, or field projects, contributing to scientific or extension publications, and presenting findings to industry and scientific audiences. Undergraduate and graduate students learned to identify anthracnose symptoms on watermelon leaves and fruits, how to operate drip irrigation systems, how to select mature, ripe watermelons for harvest, and how to isolate pathogenic fungi from diseased plant samples and preserve them as purified cultures. How have the results been disseminated to communities of interest?Overall, 21 research and extension presentations in national, regional, and state conferences and county meetings were made. Research and extension publications on the outputs of the year 1 of field trials were made. What do you plan to do during the next reporting period to accomplish the goals?In year 3, we will focus on population genomics and race-typing of the isolates collected from six states. Using molecular-markers for fungicide resistance we will screen our collection for resistance against QoI and DMI fungicides. We will also conduct integrated trials with cultivars and fungicide programs, irrigation regimes, and crop debris management.

Impacts
What was accomplished under these goals? Standardized descriptive survey and isolation protocols: In GA, we surveyed 15 commercial cucumber and 11 watermelon fields and collected over 518 isolates, which were speciated as C. orbiculare and are currently being characterized for their pathogenicity and fungicide sensitivity. PD Dutta along with Co-PD Brewer and a post-doctoral associate Kaur optimized and screened C. orbiculare collection from six states with a PCR assay developed and optimized in this project. The PCR assay was observed to be specific, sensitive and robust and can be used to detect C. orbiculare from different matrices (pure culture, plant, soil and seed samples). Co-PI Betts in Maryland, isolated 38 Colletotrichum spp. isolates from commercial watermelon fields and identified, four species (C. obiculare, C. magnum, C. chlorophyti,andC. nigrum). Co-PIs Higgins and Langston collected 108 Colletotrichum isolates in Virginia and identified 48 isolates to be C. obiculare. Race-typing: Co-PI Roberts received 25 C. orbiculare isolates from Georgia, the non-orbiculare isolates from North Carolina (C. siamense, C. scovillei, and one unidentified Colletotrichum spp.), and three industry race-typing controls from Virginia. Race-typing experiments were completed in duplicate for five Georgia isolates. The first experimental replication is complete for six additional Georgia isolates, three Florida isolates, and two race-typing controls from Co-PI Higgins in Virginia. Determination of mutations underlying QoI (cytb), MBC (β-tubulin), SDHI (sdhB, sdhC, and sdhD) and DMI (cyp51) resistance PCR primers for cytb, the target gene of QoI fungicides, were developed based on the sequenced C. orbiculare 104 genome. The gene was PCR amplified, and Sanger sequenced for ~30 isolates from watermelon, cantaloupe and cucumber with varying EC50 values for sensitivity to the QoI azoxystrobin. All watermelon isolates were wildtype at cytb, but all cucumber and cantaloupe isolates, which were generally less sensitive to azoxystrobin, had the F129L mutation known to provide partial resistance to QoIs. Fungal population genomics: To study population genetics, genomic DNA from 96 isolates was re-sequenced using Illumina at the Georgia Genomics and Bioinformatics Core in Athens, GA. These samples were submitted late-July of 2025, so we are expecting the raw reads soon. Isolates were collected between 2013 and 2024 from cucumber, watermelon, cantaloupe, and gourd hosts in Delaware, Florida, Georgia, South Carolina, and New York.An additional 96 isolates will be submitted for re-sequencing next year. Development of molecular diagnostic assays for species identification and fungicide resistance: A PCR-based marker was developed to detect the F129L mutation in cytb using the BstNI restriction enzyme, which recognizes the sequence 5′?CC/WGG?3′ and cuts between C and W (where W = A or T). In this assay, wild-type and QoI-sensitive watermelon isolates carry the BstNI recognition site and are digested by the enzyme, resulting in fragments of approximately ~400 bp and 150 bp. In contrast, cucumber and cantaloupe isolates, which have reduced QoI sensitivity, carry the F129L mutation, leading to undigested PCR products of ~550 bp. The 400 bp (sensitive) and 550 bp (partial resistance) fragments are easily distinguished by agarose gel electrophoresis. Evaluate the role of seedborne inoculum and seed-to-seedling transmission of C. orbiculare in anthracnose epidemics. Co-PI Walcott conducted a series of experiments and established seed-to-seedling transmission as well as pathogen detection protocol in artificially- and naturally- infested watermelon seeds. The role of blossom inoculation on watermelon and cucumber fruit and seed infection by C. orbiculare is currently underway. Role of crop debris and field sanitation practices in reducing cucurbit anthracnose outbreaks.To assess the role of crop debris and field sanitation practices in reducing cucurbit anthracnose outbreaks, field studies were initiated in Tifton, GA and Geneva, NY by Co-PIs Sintim and Pethybridge, respectively. Fungicide programs.Six states (GA, FL, SC, NC, VA, MD and NY) conducted evaluation of both OMRI-listed and conventional fungicides. Some of the highlights are listed below. In Virginia, inoculated field trials were conducted in 2025 at the Eastern Shore AREC in Painter, VA. From the strobilurins tested, pyraclostrobin alone and a premix of azoxystrobin and the triazole difenoconazole, significantly reduced disease compared to nontreated plots. There was no significant difference in final foliar disease severity between the strobilurin treatments but the azoxystrobin/difenoconazole premix reduced the area under the disease progress curve compared to pyraclostrobin alone. The triazoles (flutriafol, mefentrifluconazole, tebuconazole) failed to control disease, but the triazolinthione (prothioconazole) reduced disease symptoms by 50% compared to the nontreated control. Evaluation of irrigation/leaf wetness. Five states (GA, SC, NY and VA) conducted field trials with three leaf wetness treatments plus a non-treated control was set up and inoculated with a C. orbiculare race 2 isolate. Lengthening the leaf wetness periods with overhead misting at 6:00 a.m. and 6:00 p.m. significantly increased severity of anthracnose, but misting at noon did not. Evaluate host response in varietal selections and core PI collection of watermelon and cucumber lines. The bulk of the initial work for this part of the project during year 1 and 2 entailed assembling all the Plant Introduction in the cucumber and watermelon core collections developed by the USDA NIFA, SCRI CucCAP2 project. The whole genome sequences for all these 334 PI has been published and is freely available (CuGenDBv2). A manuscript describing the super-pangenome for watermelon is also available and will be helpful to develop molecular markers. Seeds for majority of the 334 Plant Introductions (PI) in the new watermelon core collection were increased at the USDA ARS, U.S. Vegetable Laboratory facility in Charleston, SC. Thirty seeds of each PI in the watermelon core collection were sent to Co-PIs McGregor and Meru. Both the collaborators have planted these large trials at their respective locations in July 2025 and will be collecting data on anthracnose development over the next two months. Co-PI Kousik have developed a Recombinant inbred Line (RIL, F11) from the cross of USVL531-MDR and USVL677-PMS. USVL531-MDR has shown resistance to anthracnose in the field whereas USVL677-PMS is highly susceptible. Data on anthracnose development on the RIL population was collected on a 0-10 scale on increasing disease severity. USVL677-PMS plants were severely infected compared to USVL531-MDR which displayed resistance. The entire RIL population consisting of 183 lines have been whole genome re-sequenced (WGS) at 26X. QTL mapping using 400,000 SNP markers and QTL2 program indicated three significant QTL's in Chromosomes 6, 7, and 8. KASP markers are being developed based on these QTLs for potential use in marker assisted selection. Economic analysis:Overall, the multi-state research trials conducted in 2024 offer valuable insights into the economic and agronomic performance of cucumber and watermelon cultivars under different production conditions in the eastern United States. Findings from Florida and Georgia highlight the significant impact of plant spacing and irrigation timing on yield and revenue, while results from New York and Virginia emphasize the crucial role of disease management and cultivar resilience. The wide variation in revenue outcomes across locations and treatments underscores the need for region-specific production strategies. These findings can serve as a foundation for growers, extension agents, and researchers seeking to enhance productivity and profitability through informed cultivar choices and targeted management practices.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Mullin A. and Betts A.K. 2025. Survey of Colletotrichum species diversity in mid-Atlantic cucurbits. Plant Health 2025 Division Student Showcase, Honolulu, HI.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Mullin A. and Betts A.K. 2025. Survey of Colletotrichum species diversity in mid-Atlantic cucurbits. APS Potomac Division Meeting Dowell, MD.
  • Type: Other Status: Published Year Published: 2024 Citation: McGregor, C. 2024. Crop Germplasm Committees: An Opportunity for Value-added Research. HortScience, S566
  • Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: McGregor, C. 2024. Crop Germplasm Committees: An Opportunity for Value-added Research. Presentation of the ASHS Annual Conference
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2025 Citation: Tsai, Y.C., Pokhrel, R., Kaur, N., Dutta, B., Brewer, M.T. High- quality genome assemblies of Colletotrichum orbiculare, a re-emerging anthracnose pathogen threatening cucurbits in the eastern U.S., Annual Meeting of the American Phytopathological Society of America, Plant Health 2025, Honolulu, HI,
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2025 Citation: Pokhrel, R., Kaur, N., Dela Cerna, C., Dutta, B., Brewer, M.T. Differences in QoI sensitivity of Colletotrichum orbiculare in the eastern United State based on cucurbit host of origin. Annual Meeting of the American Phytopathological Society of America, Plant Health 2025, Honolulu, HI
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2025 Citation: Kaur, S and Meru, G. 2025. Molecular characterization and management of Colletotrichum spp. causing Anthracnose in Florida cucurbit production. Annual Meeting of the Southern Division-American Phytopathological Society of America, Gaineville, FL.
  • Type: Conference Papers and Presentations Status: Awaiting Publication Year Published: 2025 Citation: Kaur, S and Meru, G. 2025. Impact of Anthracnose on Cucumber Yield. Annual Presentation at the Everglades Research and Education Center, Florida
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Kaur, S., Sabharwal, P., Adhikari, S., Thakur, S., Fu, Y., and Meru, G. 2025. Evaluating Yield Performance in Commercial Cucumber Varieties Under Anthracnose Pressure. Florida Society for Horticultural Sciences, Florida
  • Type: Other Status: Other Year Published: 2025 Citation: Kaur, S and Meru, G. 2025. Leveraging Genomic Tools to Improve Anthracnose Resistance in Watermelon and Cucumber. Horticultural Science Department Seminar, Gainesville, Florida, April 2025.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Kaur, S and Meru, G. 2024. Utilizing Genome Wide Association Studies to Resistance Against Anthracnose in Watermelon and Cucumber. Inter-REC Flash talk in Golf Coast Research and Education Center, Florida
  • Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: Kaur, N., Foster, M.J., Donahoo, W. M., Dutta, B. 2025. Evaluation of conventional fungicides for the management of anthracnose in cucumber in Georgia, 2024.Plant Health Progress.
  • Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: Kaur, N., Foster, M.J., Donahoo, W. M., Dutta, B. 2025. Evaluation of conventional fungicides for the management of anthracnose in watermelon in Georgia, 2024. Plant Health Progress.
  • Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: Kaur, N., Foster, M.J., Donahoo, W. M., Dutta, B. 2025. Evaluation of organic fungicides for the management of anthracnose in cucumber in Georgia, 2024. Plant Health Progress.
  • Type: Other Journal Articles Status: Under Review Year Published: 2025 Citation: Kaur, N., Foster, M.J., Donahoo, W. M., Dutta, B. 2025. Evaluation of organic fungicides for the management of anthracnose in watermelon in Georgia, 2024. Plant Health Progress.
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Khmelnitsky, O., Murphy, S., and Pethybridge, S. J. 2025. Evaluation of OMRI-listed fungicides for anthracnose control in watermelon in Geneva, NY, 2024. Plant Health Progress, https://doi.org/10.1094/PHP-03-25-0102-PDMR
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Pethybridge, S. J., and Khmelnitsky, O. 2024. Sustainable anthracnose management in watermelons: Update from NY research. USDA-SCRI Project Meeting, Myrtle Beach, SC.
  • Type: Other Status: Other Year Published: 2025 Citation: Pethybridge, S. J. 2025. Foliar diseases of cucurbits. Chatauqua County Produce Auction Winter Meeting, Sherburne, New York.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Nieland, E., Higgins, D.S., Langston, D. 2025. Evaluation of Demethylation Inhibitors, Strobilurin and Benzamidazole fungicide sensitivity in Colletotrichum orbiculare from Virginia watermelon. Plant Health, Honolulu, HI
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Higgins, D.S. 2024. Adaptive Disease Management for Vegetables. Mid-Atlantic Crop Management School, Ocean City, MD
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Vegetable Disease Management Update. Northern Neck Vegetable Growers Association Meeting, Warsaw, VA
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Higgins, D.S. 2024. Watermelon Anthracnose: 2024 fungicide and cultivar trials. Mid-Atlantic Vegetables Workers
  • Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: Nieland, E. and Higgins, D.S. 2025. Watermelon Health: Strategies for Disease Management. Richmond Area Vegetable Growers Meeting, Richmond, VA
  • Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: Nieland, E., Higgins, D.S., Langston, D. 2025. Watermelon, Hampton Roads Fruit and Vegetable Meeting, Chesapeake VA
  • Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: Higgins, D.S., and Langston, D. 2025. Watermelon Anthracnose Research Update, Grower Meeting, Capron, VA
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Nieland, E., Higgins, D.S., and Langston, D. 2025. Evaluation of Watermelon Cultivars for Susceptibility to Anthracnose, Painter, VA, 2024. Plant Health Progress, https://doi.org/10.1094/PHP-01-25-0014-PDMR.
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Nieland, E., Higgins, D.S., Langston, D. 2025. Evaluation of Watermelon Cultivars for Susceptibility to Anthracnose, Painter, VA, 2024. Plant Health Progress, https://doi.org/10.1094/PHP-01-25-0012-PDMR.
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Kumari, M., Dutta, B., Kaur, N., and McAvoy, T. 2025. Performance metrics of cucumber cultivars: Yield, marketability, and disease susceptibility, Georgia, 2024. Plant Health Progress, https://doi.org/10.1094/PHP-01-25-0018-PDMR.
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Kumari, M., Dutta, B., Kaur, N., and McAvoy, T. 2025. Optimizing overhead irrigation schedules for effective anthracnose management in watermelon, Georgia, 2024. Plant Health Progress https://doi.org/10.1094/PHP-01-25-0019-PDMR.
  • Type: Other Journal Articles Status: Published Year Published: 2025 Citation: Kumari, M., Dutta, B., Kaur, N., and McAvoy, T. 2025. Evaluation of anthracnose disease resistance, yield performance, and fruit size distribution of seedless watermelon cultivars in Georgia, 2024. Plant Health Progress, https://doi.org/10.1094/PHP-01-25-0020-PDMR
  • Type: Other Status: Published Year Published: 2025 Citation: Thompson, C. 2025. Attacking Anthracnose: UGAs Dutta Highlights Research in Watermelon Disease. Vegetable and Specialty Crop News
  • Type: Other Status: Published Year Published: 2025 Citation: Thompson, C. 2025. UGA Studying Anthracnoses Impact in Cucurbits Vegetable and Specialty Crop News
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Keinath, A. 2025. Field Scouting and Disease Identification on Watermelon, Cantaloupe, Cucumber, and Squash. Clemson Extension Preplant Cucurbit Meeting, Edisto REC, Blackville, SC
  • Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: Dutta, B. 2025. Fungicide options and improved cultural practices in managing anthracnose in watermelon. Southeast Fruit and Vegetable Conference, Savannah, GA
  • Type: Conference Papers and Presentations Status: Other Year Published: 2025 Citation: Higgins, D.S. and Langston, D.L. 2024. Anthracnose, Downy Mildew, and Gummy Stem Blight Disease Management for Virginia Watermelons. Capron Area Watermelon Growers, Capron, VA
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Dutta, B. 2025. Anthracnose Management in Cucurbits. Southeast Fruit and Vegetable Conference, Savannah, GA
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Dutta, B. 2024. SCRI-SAM, an overview and impact of a collaborative project in the eastern US. Southeast Vegetable Expo, Myrtle Beach, SC
  • Type: Conference Papers and Presentations Status: Published Year Published: 2025 Citation: Rideout, S.L., C. Saint-Preux, K. Belesimo, and M. Whittimore. 2025. Polyoxin D Zinc Salt (OSO 5%SC) offers organic vegetable growers improved disease control. Annual American Phytopathological Society Meeting, Honolulu, HI.
  • Type: Other Status: Other Year Published: 2025 Citation: Rideout, S.L. 2025. Vegetable Disease Update. South Central Vegetable Production Meeting, Buckingham, VA
  • Type: Other Status: Other Year Published: 2025 Citation: Dutta, B. 2025. Management of vegetable diseases in southern Georgia, Tift County Annual Extension Meeting. Tifton, GA
  • Type: Other Status: Other Year Published: 2025 Citation: Dutta, B. 2025. Improved management options for vegetable crops in Georgia, Colquitt County Annual Extension Meeting. Moultrie, GA
  • Type: Websites Status: Published Year Published: 2025 Citation: Dutta, B. 2025. SCRI-SAM Webpage. https://site.extension.uga.edu/cucurbitanthracnose/sample-page/


Progress 09/01/23 to 08/31/24

Outputs
Target Audience:Primary audience of the project is the cucurbit producers in the easternUnited States. This includes watermelon and cucumber producers, packers, shippers, agronomists, crop consultants, farm managers, field workers, seed companies, and dealers; and watermelon and cucumberstorage and shipping/transport personnel and companies. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training opportunities were provided for postdocs, graduate students, and undergraduates in plant pathology, genomics, bioinformatics, and extension. These opportunities include conducting thesis or dissertation research, participating in computational, laboratory, greenhouse, or field projects, contributing to scientific or extension publications, and presenting findings to industry and scientific audiences. Undergraduate and graduate students learned to identify anthracnose symptoms on watermelon leaves and fruits, how to operate drip irrigation systems, how to select mature, ripe watermelons for harvest, and how to isolate pathogenic fungi from diseased plant samples and preserve them as purified cultures. How have the results been disseminated to communities of interest?Initial findings of the project were disseminated via various means including regional and state conferences and grower meetings. What do you plan to do during the next reporting period to accomplish the goals?We plan to make progress in activities listed for each objective and routinely disseminate findings via various outlets.

Impacts
What was accomplished under these goals? Standardized descriptive survey and isolation protocols: Protocols for survey and pathogen isolations were developed. In GA, we surveyed five commercial cucumber and three watermelon fields and collected over 150 isolates, which are currently in the process of being speciated and characterized for their pathogenicity and fungicide sensitivity. PD Dutta along with Co-PD Brewer and a post-doctoral associate Kaur has developed a PCR based assay for specific and sensitive detection of Colletotrichum orbiculare. Co-PI Queseda-Ocampo has also developed a semi-selective medium for selective recovery of C. orbiculare from plant samples. Co-PIs Roberts and Vallad surveyed commercial watermelon and cucumber fields in Florida and collected 39 isolates from six counties. Co-PI Queseda-Ocampo has collected 50 isolates from four commercial cucumber and watermelon fields in NC. Race-typing: Differential seeds were obtained and shared with other Co-PIs. A permit for Co-PI Roberts to receive out of state Colletotrichum isolates was submitted but has not yet been approved. Co-PI Roberts have completed germination testing and are now conducting the initial race-typing with a single-spored isolate from North Florida. Preliminary results are expected in October 2024. Determination of mutations underlying QoI (cytb), MBC (β-tubulin), SDHI (sdhB, sdhC, and sdhD) and DMI (cyp51) resistance: A rotating (4-week rotation) graduate student in Co-PD Brewer's lab has developed PCR primers for cytb based on the sequenced C. orbiculare 104T genome. The graduate student amplified and Sanger sequenced cytb for 9 isolates from watermelon, cantaloupe and cucumber with varying EC50 values for sensitivity to the QoI azoxystrobin. It was found that all watermelon isolates were wildtype at cytb, but all cucumber and cantaloupe isolates, which were generally less sensitive to azoxystrobin, had the F129L mutation known to provide partial resistance to QoIs. The PhD student who started August 10, 2024, will be developing an allele-specific PCR-based marker for this mutation and testing it on a panel of isolates from multiple states with varying EC50 values. Fungal population genomics: A postdoctoral researcher working on this objective joined the lab August 1, 2024. She has begun high quality DNA extractions for PacBio sequencing of select isolates. Evaluate the role of seedborne inoculum and seed-to-seedling transmission of C. orbiculare in anthracnose epidemics. Co-PI Walcott is optimizing DNA extraction protocol and a PCR assay to ensure the highest levels of C. orbicularedetection sensitivity and specificity from seed lots. In the interim, Co-PI Walcott is optimizing protocols for artificial seed infestation and seed-to-seedling transmission assays with C. orbiculare. Role of crop debris and field sanitation practices in reducing cucurbit anthracnose outbreaks.? To assess the role of crop debris and field sanitation practices in reducing cucurbit anthracnose outbreaks, field studies were initiated in Tifton, GA and Geneva, NY by Co-PIs Sintim and Pethybridge, respectively. The study entails three crop debris management systems: (a) crop debris left on the soil surface; (b) crop debris incorporated after harvesting; and (c) crop debris completely removed after harvest. The treatments were arranged in a randomized complete block design with four replications, and each treatment plot had three beds to ensure adequate buffer. All sampling and data collection will be made from the middle bed. The fields were planted to cucumber in Tifton and watermelon in Geneva, and the management systems (treatments) were imposed shortly after harvest in Tifton. The treatments will be imposed in mid-September in Geneva. Next year (2025), experimental plots will be planted to cucumber and watermelon, respectively in Tifton and Geneva, to assess treatment impact on cucurbit anthracnose control. This represents a worst-case scenario for anthracnose outbreak, given that growers would typically plant cucurbit in rotation with other crops. Therefore, a positive treatment response would reflect a very effective management system. We hypothesized that crop debris removal for cucurbit anthracnose control would not adversely impact soil health and overall carbon sequestration given the low residue biomass and rapid mineralization. Residues of fresh produce tend to mineralize rapidly because of the high moisture content and low C:N ratio. To test the above hypothesis, soil health assessment and soil carbon measurements were made before treatment imposition. Another assessment will be made in the final year of the study. Fungicide programs.PD-Dutta conducted two trials evaluating efficacy of 10 OMRI-listed products on managing anthracnose in watermelon and cucumber (Tifton, GA). None of the OMRI-listed products provided effective reduction in anthracnose severity compared to the non-treated control. Co-PIs Higgins and Langston conducting a 12-treatment single product fungicide efficacy trial in Painter, VA. Fungicide treatment is expected to be initiated in September and the trial is expected to be completed in October 2024. Co-PIs Higgins and Langston also conducting a 10-treatment commercial variety trial in Painter, VA. The trial is expected to be completed in October 2024. In SC, Co-PI Keinath conducted a fungicide efficacy trial with 10 fungicides and 2 non-treated controls. Despite inoculation of interplot spaces with a C. orbiculare race 2 isolate, anthracnose symptoms were found in only four plots. Data for disease severity were collected and are currently being analyzed. Co-PI Vallad conducted two field trials on cucumbers, evaluating ten conventional and ten biological fungicides. Limited separation between treatments and the untreated control was likely due to early-season herbicide damage. In the conventional trial, Cabrio (FRAC 11) showed superior performance. Evaluation of irrigation/leaf wetness. Co-PI Keinath in SC conducted a field trial with three leaf wetness treatments plus a non-treated control was set up and inoculated with a C. orbiculare race 2 isolate. Lengthening the leaf wetness periods with overhead misting at 6:00 a.m. and 6:00 p.m. significantly increased severity of anthracnose, but misting at noon did not. Evaluate host response in varietal selections and core PI collection of watermelon and cucumber lines.Co-PI Kousik has increased seeds for over 300 watermelon PI lines and around 220 cucumber PI lines. These seeds will be provided to breeders involved in this project for their evaluation in 2025 season. All these PI lines have been whole genome re-sequenced by CucCAP. Evaluation of commercial cultivars for anthracnose resistance is currently underway in GA, FL, VA, NY and DE. Data for disease severity and yield will be collected in September 2024. Economic analysis. In anticipation of the data from the project's first year of field experiment trials becoming ready for economic analysis in year two of the project, data collection began to acquire market prices for watermelon and cucumber across the different states considered in the project as well as input costs for products considered in the field trials. Additionally, a literature review was conducted for previous studies related to watermelon and cucumber conducting an economic analysis related to anthracnose management. Although there is a literature testing different management strategies for anthracnose, including different inputs and timing of management strategies, the literature has largely focused on the impact in disease rates, rather than the revenue-cost equation for producers.

Publications

  • Type: Websites Status: Published Year Published: 2024 Citation: https://site.extension.uga.edu/cucurbitanthracnose/sample-page/
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Higgins, D.S. and Langston, D.L. 2024. Anthracnose, Downy Mildew, and Gummy Stem Blight Disease Management for Virginia Watermelons. Capron Area Watermelon Growers, Capron, VA.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Dutta, B. 2024. Update on watermelon and cucumber anthracnose. Southeast Fruit and Vegetable Growers Conference, Savannah, GA.
  • Type: Other Status: Other Year Published: 2024 Citation: Dutta, B. 2024. Fungicide update on cucurbit anthracnose. Southeast Fruit and Vegetable Growers Conference, Savannah, GA.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2024 Citation: Alshwaiki, G., Hagerty, A., Cochran S., Quesada-Ocampo L. M. 2024. Diversity of Fungal Plant Pathogens on North Carolina Cucumbers. Undergraduate Research and Creativity Symposium. NC State, Raleigh, NC.