Evaluation of Prophyt, alone and in combination, for post-infection control of downy mildew on basil, Fall 2007

摘要

Sweet basil of the variety ’Martina’ was planted in a 0.4-A commercial field 25 milessouth of Clewiston, FL on 9 Oct. The soil, classified as Immokalee fine sand with a soil pH of 7.4, was fertilized according to soil test recommendations. Basil was direct-seeded in four rows with a 10-in. row spacing on top of 8-in. raised beds formed on 6-ft centers. Seeds were densely planted and final plant spacing within the row was approximately 1-in. The experiment consisted of a randomized complete block design with three replications of ten treatments. Experimental units were 4-row, 6-ft bed sections, separated on the end by 4-ft alleys. Chemical treatments were applied using a CO2 backpack sprayer. The hand-held boom was equipped with three Tee-Jet 11003 flat-fan nozzles. Foliar sprays were applied at 30 psi, delivering a final spray volume of 62 gal/A. Fungicide treatments commenced on 29 Oct at the 6-7 leaf stage, with one subsequent application on 5 Nov. A nonionic surfactant, Induce, was added at a rate of 0.125% v/v to assist coverage. Disease pressure arose from natural inoculum and itis significant to note that downy mildew was observed in the trial area on the date of initial application, but visual incidence was low. Downy mildew was initially assessed on 6 Nov by randomly collecting ten leaves per experimental unit from the firstnode above ground level. Disease severity was calculated by visually estimating the percent leaf area exhibiting downy mildew signs or symptoms. Leaves were stored under refrigerated conditions (50 F) until 19 Nov, when downy mildew was re-assessed. Severity data were transformed using the arcsine transformation prior to analyses. In addition, whole plant ratings were conducted in the field on 18 Nov by using a 0-10 scale, with 0 representing no disease and 10 representing downy mildew throughout the entire canopy. Whole plant ratings were performed on the two central rows at two randomly selected locations per experimental unit.