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Funded Project |
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Funding Program:
IPM Enhancement Grants |
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Project Title:
IPM program for the new bacterial disease on watermelon in Florida caused by Pseudomonas syringae |
Project Directors (PDs):
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Lead State: FL Lead Organization: University of Florida Board of Trustees |
| Undesignated Funding: $28,851 |
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Start Date: Jan-01-2014 End Date: Dec-31-2014 |
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Pests Involved: Pseudomonas syringae |
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Site/Commodity: Florida Watermelon |
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Area of Emphasis: IPM |
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Summary:
Florida is the largest producer of watermelon in the United States with 24,000 acres under production and a farm value of $138 million. A new bacterial disease on watermelon was discovered in the spring season production in 2013 from Suwannee, Jackson, Hendry, Levy, Gilchrist, Alachua, and St. Johns counties in Florida. The key symptom is the circular lesions with white to tan centers that led to severe leaf blighting. Under the microscope, cut section of the lesions indicated heavy bacterial streaming. The disease affected watermelon in an estimated 6,500 acres in Florida. Pure colonies of 20 bacterial strains were isolated from all watermelon samples collected from these counties. Among these strains 12 were highly pathogenic on watermelon and caused a disease severity of >60% on watermelon seedlings; the remaining strains caused a lower disease severity. Preliminary characterization of the bacteria using LOPAT analysis, Gas-Chromatography Fatty Acid Methyl Ester Analysis, and DNA sequencing confirmed the pathogen as Pseudomonas syringae strains. Further DNA-sequencing using Multi Locus Sequence Typing is in progress for pathovar level characterization. Over the past many years bacterial diseases on watermelon including bacterial fruit blotch and angular leaf spot has been successfully managed using copper. However, the currently recommended watermelon spray schedule in Florida does not include use of copper due to minimal issues with bacterial diseases. Acibenzolar-S-methyl (ASM; Actigard®) is a SAR inducer and works by activating the plants defense system by increasing the transcription of stress related genes. Actigard is known to increased resistance of watermelon to bacterial fruit blotch and angular leaf spot. However, the effectiveness of actigard on the new P. syringae strains in the 2013 outbreak is not known. This necessitates the development of a new watermelon IPM program for effective disease management in 2014. Copper can be effectively used on watermelon for management of bacterial diseases, but should be carefully managed due to potential phytotoxicity and bacterial resistance issues. Preliminary in vitro studies on the effect of copper on the bacterial strains isolated from the 2013 outbreak indicated that most of the strains (6 out of 7 strains) were highly sensitive to copper at 80 ppm, while one strain was resistant to copper at the same concentration. In two repeated experiments conducted in greenhouse conditions with a highly pathogenic strain of the bacterium from the 2013 outbreak in Florida, we found that actigard significantly reduced the severity of the new bacterial disease compared to non-treated watermelon seedlings at rates corresponding to 0.5 oz/A and higher. This proposed project plans to use these preliminary findings to develop an IPM program including use of copper, copper + ethylene bis thiocarbamate, and actigard (drip & foliar). Field trials will be conducted at two locations in Florida, and the findings will help growers in the southern region of United States to initiate a preventative IPM program that minimizes potential yield losses due to this new bacterial disease on watermelon.
Objectives: Objectives of the proposal: 1. To test the sensitivity of the bacterial strains associated with the new bacterial disease on watermelon to copper and effectiveness under field conditions 2. To evaluate the effectiveness of Systemic Acquired Resistance (SAR) inducers in reducing the severity of the bacterial disease under field conditions. 3. To develop an IPM strategy incorporating copper and SAR inducers for disease management under field conditions 4. To transfer knowledge gained from the developed IPM strategy and training Florida growers on cultural practices and fungicide management program for disease management. The overall goal of the project to develop techniques for effective management of the new bacterial disease caused by Pseudomonas syringae strains on watermelon in Florida and all other states in the southern region. |
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Final Report: |
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Impacts Impact: Many growers in North Florida have started using Copper + Mancozeb in their new IPM spray program since spring 2014 based on utilizing disease management strategies recommended based on our research findings. The growers who attended our training programs produced watermelon in ~6500 acres in 2014. These growers are now focused on using cleaner transplants in spring 2015 and using the IPM strategy; the impact of this will be assessed in summer 2015. The key aspects in change in knowledge, practice and yield and/or disease reduction impact will be assessed this year. |
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Outcomes Relevant to Objective 1: To test the sensitivity of the bacterial strains associated with the new bacterial disease on watermelon to copper Outcome: Bacterial sensitivity to copper was completed for 47 strains collected from Florida and Georgia in 2013 and 2014. All the strains were found to be copper sensitive. Relevant to Objective 2: To evaluate the effectiveness of Systemic Acquired Resistance (SAR) inducers in reducing the severity of the bacterial disease Outcome: SAR inducer significantly reduced disease severity compared to untreated control in both field trials conducted in Florida in spring 2014. SAR inducer also increased yield in one of the field trials. Relevant to Objective 3: Develop an IPM strategy incorporating copper and SAR inducers for disease management under field conditions Outcome: Use of clean transplants is critical in successful production and management of Pseudomonas syringae leaf spot on watermelon as indicated in both the field trials with the disease severity significantly lower when clean transplants were used compared to infected transplants. Copper+Mancozeb/Copper by itself was the best treatment in the field trials conducted in 2014 and significantly reduced the disease compared to the untreated control. Bacillus subtilis (bio-control agents; BCA) strain also significantly reduced disease severity. Incorporation of Copper+Mancozeb with SAR inducers and BCA is currently being investigated for maximizing efficacy in disease management. Relevant to Objective 4: Transfer knowledge gained from the developed IPM strategy and training Florida growers on cultural practices and bactericide management program for disease management Outcome: The findings from the study were presented at the following meetings. The number of attendees are in parenthesis a. Suwannee Valley Watermelon Institute Meeting, Gainesville, FL 2013 (100+) b. Suwannee Valley Watermelon Institute Meeting, Gainesville, FL, 2014 (150+) c. Tri-state Cucurbit meeting, Marianna, FL, 2014 (42) d. Tri-state Cucurbit Meeting, Marianna, FL, 2015 (56) |
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