Evaluation of fungicides to control Sclerotinia drop in lettuce, 2008.

摘要

The experiment was conducted at the Ohio Agricultural Research and Development Center’s Muck Crops Agricultural Research Station in Celeryville, OH on Linwood muck soil, pH 5.6. Fertilizer (18-17-17, 250 lb/A) was incorporated into the test field on25 Apr.Plots were disked, leveled and raised beds on 6 ft centers were prepared on 17 Jul. ‘Tehama’ lettuce seeds were direct seeded on 31 Jul. Plots were arranged in a randomized complete block design with four replications. Each plot consisted of three, 20ft rows with 18 in. row spacing on 6 ft centers seeded at a rate of 10 seeds/ft. After seedlings germinated, they were thinned to one plant every 10 in. Treatmentswere applied using a tractor mounted 3.0 hitch (hydraulic attach) motor driven sprayer (40 psi, 42.6 gal/A, 2 mph) on a 5-7 day schedule beginning 18 Sep and ending 28 Oct for a total of seven applications. The insecticide Sevin XLR Plus (1 qt/A) was applied on 22 and 29 Aug. Plants were inoculated with a homogenized mycelial suspension of Sclerotinia minor on 25 Sep using a backpack CO2-pressurized sprayer. Inoculum was prepared by homogenizing mycelia from a 7-day-old S. minor culture grown on PDA medium in distilled water.Plants were overhead irrigated with 0.7 in. water on 1 and 29 Aug and 4 Sep, and with 1.1 in. water on 13 Aug. Healthy plants and plants with drop symptoms from the treated or control plots were counted on 15, 22, and 27 Oct and 5 Nov. Average maximum temperatures for 31 Jul, Aug, Sep, Oct, and 1-18 Nov were 87.7, 80.6, 77.4, 62.2, and 68.4deg F; average minimum temperatures were 75.7, 57.3, 53.0, 38.5, and 42.8deg F; and rainfall amounts were 0.0, 0.9, 4.1, 1.1, and 0.0 in., respectively. Data were analyzed by ANOVA using SAS statistical software. Means were separated using Fisher’s protected least significant difference test.