Evaluation of Organic Control Products for Basil Downy Mildew

View the project final report

• 2011 annual report

Commodities

• Additional Plants: herbs

Practices

• Pest Management: biological control, biorational pesticides, botanical pesticides, prevention

Downy mildew of basil is a new and important disease in the eastern United States. It was first identified in Florida in 2007. Many farms in the northeast had severe outbreaks in 2008 and 2009. There is currently no published research on the efficacy of disease control products available for organic farmers for this disease. In the proposed study, five products labeled for basil and for control of downy mildew will be tested on two basil cultivars, one highly susceptible and one less susceptible (based on a cultivar trial done in New Jersey in 2010). Organic farming relies heavily on cultural practices to reduce disease and pest problems. Control products can be used to complement these practices on susceptible cultivars or when disease pressure is high. Including two cultivars with different susceptibility to downy mildew will provide valuable information on the effectiveness of the products in an integrated pest management program. The products that will be included in the proposed study are Serenade MAX, Actinovate, Trilogy, OxiDate and Milstop. Trials will be conducted in the field at two locations, Community Farm of Simsbury in Simsbury, CT and University of Connecticut Plant Science Research Facility in Storrs, CT.

This research project will evaluate the efficacy of five organic disease control products for control of basil downy mildew in the field. These five treatments and a control will be applied to two species of basil. O. basilicum cultivar ‘Genovese’ (susceptible) and O. citriodorum cultivar ‘Lemon’ (less susceptible) will be grown from seed from High Mowing Organic Seeds. A randomized complete block design with four replicates will be used at each of two locations, Community Farm of Simsbury in Simsbury, CT and the UConn Plant Science Research Facility in Storrs, CT.

Six week old transplants will be placed in beds with four 6-foot rows per treatment. Plants will be spaced 8” apart within the rows with a between-row spacing of 18-24”. Treatment sections will be separated by mowed 4-foot strips. Drip irrigation or hose irrigation at the base of the plants will be used in combination with an organic mulch to control weeds and conserve water. Fertilizer will be applied based on soil test results. If phosphorus and potassium are at recommended levels, nitrogen will be supplied using Espoma dried blood at a rate of 2 lbs/100 ft2 as needed. If necessary, a balanced organic fertilizer will be applied at the recommended rate. Basil seedlings will be transplanted to the field after danger of frost has passed in late May to early June.

Preventive applications of each treatment will be applied at 7-day intervals beginning in late June based on the first detection of the disease in early July in 2010. If weather is extremely favorable for disease, treatments may begin earlier. Likewise, if weather is extremely unfavorable for disease, spray intervals may be extended to 10-14 days. These spray intervals are consistent with label recommendations. Products will be applied using a CO2 backpack sprayer. The handheld boom will be equipped with three Tee-Jet 11003 flat-fan nozzles adjusted to provide thorough coverage of the plant including the undersides of the leaves. The equipment will be calibrated to deliver 60 gallons per acre at the rate recommended on the label. An adjuvant will be added to the Serenade MAX and Actinovate treatments as recommended by the manufacturers. It is estimated that there will be 14 applications for the season. All products will be applied at recommended rates for downy mildew.

Treatments, their application rates and active ingredients to be included are shown in attached file "Treatment Rates" below. Infection of plants will be by naturally occurring inoculum. Disease appeared naturally in Connecticut by early July of 2010 when weather conditions were mostly unfavorable for the pathogen. Plants will be monitored to document the date of the onset of infection in the study plots. Disease incidence will be measured by estimating the percentage of plants in each treatment that show symptoms or signs of downy mildew. Disease severity will be evaluated using a scale from 0-3 as follows: 0 = no symptoms or sporulation present, 1 = symptoms present without sporulation, 2 = symptoms present with light sporulation, and 3 = symptoms present with heavy sporulation. Plants in the center two rows of each treatment will be rated. Incidence and severity will be recorded twice, once in August and once in September. Statistical analysis of the results will be done using SAS software to compare yield and disease incidence and severity for each treatment. Dr. Thomas Morris and Dr. John Inguagiato of the University of Connecticut Department of Plant Science and Landscape Architecture will assist with statistical analysis of the results.

The results of this study ‘Evaluation of Organic Control Options for Basil Downy Mildew’ will be shared with farmers and other outreach and research professionals through a variety of publications and presentations including fact sheets, bulletins/newsletters and meetings. Scientists at University of Florida and Cornell have agreed to share the results through their fact sheets, meetings or websites. These are scientists who are also involved in research or monitoring of basil downy mildew (Richard Raid, Univ. of Florida, Meg McGrath, Cornell). Rick Raid will share the results with growers in Florida at regularly held grower meetings. Meg McGrath suggested sharing the results in a shared report on the disease on eOrganic, a web-based agriculture resource (http://eorganic.info/). Study results will also be shared as either a power point presentation or poster at meetings that may include the New England Vegetable and Fruit Growers Conference, the annual meeting of the Northeast Plant Diagnostic Network, the next meeting of the National Plant Diagnostic Network, the annual meeting of the Northeast Division of the American Phytopathological Society, NOFA annual winter conference 2012, and/or the annual Connecticut Vegetable & Fruit Growers Conference. Newsletters and publications may include CT NOFA newsletter ‘Gleanings’, ‘The Natural Farmer’ (NOFA and CTNOFA outreach opportunities were suggested by Bill Duesing, Executive Director of CTNOFA),and ‘Crop Talk’, the UConn Extension Commercial Vegetable and Fruit Crops Newsletter. Results will also be submitted to Plant Disease Management Reports, published by the American Phytopathological Society.

• Treatments, application rates & active ingredients.