Timing Fungicidal Control of Sclerotinia minor Causing Drop of Lettuce Grown on Organic Soils in New York. L. A. Wymore, Graduate Research Assistant, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853. J. W. Lorbeer, Professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, NY 14853. Plant Dis. 70:1134-1138. Accepted for publication 14 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1134.

The dicarboximide fungicides vinclozolin (Ronilan 50WP) and iprodione (Rovral 50WP) were effective in controlling Sclerotinia minor causing drop of lettuce grown on organic soils in New York. Weekly sprays with vinclozolin at 1.12–1.68 kg/ha (2–3 lb/acre) beginning 3 wk after planting and continuing until 1 wk before harvest provided the best control of all fungicides and schedules tested. Infection of lettuce by S. minor generally did not occur until about 2.5 wk before harvest, and infections taking place less than 1 wk before harvest often did not result in unmarketable lettuce heads. Under these conditions, effective control of lettuce drop was achieved with as few as three sprays with vinclozolin beginning 1–2 wk after thinning and continuing for a total of three consecutive weekly sprays.

Keyword(s): Lactuca sativa.