Evaluation of Organic Control Products for Basil Downy Mildew

Evaluation of Organic Control Products for Basil Downy Mildew

Summary

Eight week old basil seedlings were transplanted into research plots at two Connecticut locations in June. Monitoring for downy mildew was done weekly and control products were applied preventatively beginning July 27th and 28th. Disease was confirmed in the field at both locations in early August. Products were applied weekly (twice weekly for OxiDate once disease was detected, at one site only). Treatments were applied for five weeks. Disease was evaluated during the week after the final treatment. The partner farmer participated in growing the basil transplants and bed preparation, planting the seedlings, mulching, weeding, applying the treatments, and disease evaluation at Community Farm of Simsbury. The results varied between the two sites. Milstop performed the best at both locations. OxiDate treated plants were also less diseased than the control plants at both sites. Actinovate, Serenade and Trilogy all resulted in significant differences from the control at one of the two sites but not the other. The results of the study have been presented during the Extension and Industry session at the October 2011 meeting of the Northeast Division of the American Phytopathological Society and have been submitted to Plant Disease Management Reports for publication. The results will also be shared with growers in the northeast and elsewhere through newsletters.

Objectives/Performance Targets

The objective of this project was to compare five organic control products for management of basil downy mildew. 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. The results of this study add valuable information to this body of work. Using the results of this study, basil growers that have had problems with downy mildew in the past can use some of the products tested knowing that under the conditions of this study, sufficient control was achieved to preserve the marketability of the basil.

Accomplishments/Milestones

The project overall has gone as planned. The first activity after purchasing necessary supplies and materials was to grow the basil transplants. We planned to grow them in a high tunnel at Community Farm of Simsbury but it was crushed by the large amounts of snow last winter in the area. The seedlings were started instead in a greenhouse at a local school. The greenhouse space was only available temporarily so the very young seedlings were moved out to the high tunnel which was not yet repaired, so essentially outside. The weather during the following few weeks was very cool and rainy and the transplants, especially the lemon basil, were not very vigorous. Because of this, there was only enough lemon basil to use for plots at one of the two research sites. We did have enough sweet basil for both sites as planned. Bed preparation and planting went well, and between row spaces were mulched with mulch 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 the planned rates. The only variation was that OxiDate was applied twice weekly late in the experiment per the recommendation of the manufacturer representative. He requested this as soon as disease was confirmed but rainy weather prevented it with the exception of one week at Community Farm of Simsbury. In addition to increasing the frequency of applications, it was recommended to apply double the amount (OxiDate only) at this time which was done. The original intention was to apply treatments into mid September before evaluating disease. Tropical storm Irene came through on August 28th and knocked over most of the sweet basil plants at both locations. Disease was then evaluated at both locations within one week. The lemon basil, which was known from previous work to be less susceptible to downy mildew than the sweet basil, had some symptoms that could have been downy mildew but no sporulation at this point so disease was not evaluated on those plots. Symptoms only could also be a nutrient deficiency. The results of the trial showed significant differences between some of the treatments and the control that will be helpful to growers selecting management tools for basil downy mildew.

• Treatment application at CFS
• Basil at UConn mid July
• Sweet basil after storm Irene

Impacts and Contributions/Outcomes

A preliminary report on the results was presented to a meeting of Integrated Pest Management faculty and staff of UConn in September. In October, a power point presentation was given on the results at the Extension and Industry Session of the annual meeting of the Northeast Division of the American Phytopathological Society. A paper summarizing this project and its results has been submitted for publication to Plant Disease Management Reports. Additionally, results will be shared with growers in the northeast and elsewhere via grower newsletters in cooperation with other researchers in Florida and at Cornell University. Approximately 50 Master Gardeners learned about the project during their summer field day at the UConn Research Farm where they visited my plots and I gave an overview of the work. At Community Farm of Simsbury (CFS), a certified organic farm, 30 middle school students involved in the farm’s summer camp on the environment visited and learned about the plots and the research. There are also incubator farmers at CFS who were knowledgeable about the study and its purpose. These organic farmers in training were also growing basil and other crops susceptible to downy mildews.

Collaborators: