Management of basil downy mildew using organic fungicides and nitrogen fertilization rate

Management of basil downy mildew using organic fungicides and nitrogen fertilization rate

Summary

Seven week old basil seedlings were transplanted into research plots at two Connecticut locations in early July. Monitoring for downy mildew was done weekly and control products were applied preventatively beginning August 2nd and 3rd. Disease was confirmed in the field at both locations in early August during the second week of treatments. Products were applied weekly. Treatments were applied for five weeks at Community Farm of Simsbury (CFS) and six weeks at the University of Connecticut Plant Science Research Farm (UConn). Nitrogen was applied in fish meal (8-12-12) and blood meal (12-0-0) just prior to planting at rates of 50, 90 and 120 lb/ac. Fish meal was applied equally to all plots so P and K additions would be equal and the balance of the required N was applied as blood meal for the two higher N rates. All plots received a side dress of N (blood meal) at 30 lb/ac seven weeks after planting. Disease was evaluated during the week after the final treatment at UConn and two weeks after the final treatment at CFS. The partner farmer participated in growing the basil transplants and bed preparation, planting the seedlings, applying fertilizer, mowing weeds between beds, and applying the treatments. The results varied between the two sites. This year there were no significant differences between fungicide treatments and the control at UConn. At CFS, OxiDate provided some reduction in disease severity. OxiDate also reduced disease severity at both sites in 2011. At CFS, disease severity was lower at higher rates of nitrogen fertility. At UConn, disease severity was greater at the highest nitrogen application rate. These conflicting results make it impossible to conclude whether nitrogen fertility has a consistent effect on basil downy mildew severity. The results of this study and last years’ will be presented at the 2013 Connecticut Vegetable and Fruit Growers Conference and the 2013 meeting of the Northeast Division of the American Phytopathological Society. The UConn basil downy mildew factsheet that was written based on last year’s work will be updated to include this new information.

• Spray application at CFS. 8/15/12
• CFS basil plots showing beds and irrigation 8/15/12.
• Basil downy mildew symptoms. CFS 8/15/12

Objectives/Performance Targets

The objectives of this project were to compare organic control products for management of basil downy mildew including the addition this year of Cueva (A.I. copper octanoate) and to determine if nitrogen fertility had an effect on disease severity. Research based information on efficacy of these products is needed for this important disease so growers can get the needed control with reduced cost and reduced pesticide use and follow the requirements for organic certification. If nitrogen fertility has an effect on disease severity, then fertilization practices could be part of an integrated management plan. Using the results of this study, basil growers that have had problems with downy mildew in the past can make more well-informed management decisions.

Accomplishments/Milestones

The project overall has gone as planned. The first activity after purchasing necessary supplies and materials was to grow the basil transplants. Bed preparation and planting went well. At CFS, a bed maker was used to create raised beds using drip irrigation and black plastic mulch. At UConn, beds were in the ground and mulched with hay. The seedlings had a nearly 100% survival rate and thrived in the field. Applications of control treatments commenced just prior to disease detection in the field as planned. Five weekly applications were applied at CFS and six at UConn. For the treatment alternating OxiDate and Actinovate, OxiDate was used during the first week and the products were alternated every other week thereafter. Disease incidence was nearly 100% in the field at CFS by the second week of treatments. Disease was detected this same week at UConn but incidence was less than 50%. Disease was evaluated at UConn one week after the final sprays and two weeks after at CFS. The results of the trial showed no significant differences between fungicide treatments and the control at UConn and only OxiDate reduced disease severity at CFS this year.

Impacts and Contributions/Outcomes

In January 2013, the results of both this and last year’s work will be presented at the Connecticut Vegetable and Fruit Growers Conference. The average number of growers attending is 150. Another presentation will be given at the Business and Extension meeting during the 2013 annual meeting of the Northeast Division of the American Phytopathological Society. Additionally, results will be shared with growers in the northeast and elsewhere via grower newsletters in cooperation with other researchers. An article will be submitted for the newsletters of the Northeast Organic Farming Association (NOFA). A report of the results has been submitted to Plant Disease Management Reports, an online publication of the American Phytopathological Society.

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