Evaluation of fungicides for control of Sclerotinia drop of lettuce, Waynesville 2008.

摘要

The experiment was conducted at the Mountain Research Station in Waynesville, NC (N35deg31.897’; W082deg57.758’). Plots were bare ground double row beds on 42 in. centers, 20 ft long with 5-ft fallow borders at each endand non-treated guard rows on each side. Lettuce was seeded in the greenhouse on 10 Apr and transplanted in the field on 19 May in double rows spaced at 12 in apart with 12 in. plant spacing within the row. Irrigation was applied via drip tape.Treatments were randomized into four complete blocks. On 3 Jun, plots were infested by spreading 100cc of S. sclerotiorum infested oat grain and incorporated into the top 1 in. of soil. Fungicide treatments were applied using a CO2-pressurizedbackpack sprayer equipped with a 2-nozzle (19 in. spacing), handheld boom with hollow cone nozzles (TXVS-26) delivering 40 gal/A at 45 psi. Applications were made on a 14-day interval: 4 and 19 Jun. Lettuce drop severity was evaluated on 12,19, and 25 Jun, and 1, 9, 14, and 24 Jul. Disease severity was assessed as number of plants collapsed/diseased per plot due to S. sclerotiorum. Average monthly high and low temperatures (Fdeg) for 2008 (1971-2000 year average) were 72/48 (73/46) inMay, 82/55 (80/53) in Jun, and 82/57 (83/57) in Jul. Rainfall (in.) for 2008 (1971-2000 year average) was 1.64 (4.43) in May, 0.62 (4.03) in Jun, and 1.93 (3.59) in Jul.