Performance of Products for Management of Sclerotinia Leaf Drop of Lettuce in 2002

Abstract

Sclerotinia leaf drop in Arizona is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperature favor this disease. Some new products in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 2001-2002. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. Significant reduction of Sclerotinia leaf drop caused by S. minor occurred in plots treated with Endura, whereas other products tested against this pathogen did not significantly reduce the level of disease compared to nontreated control plants. The highest level of disease reduction in plots infested by S. sclerotiorum was achieved by the fungicide Ronilan as well as the biological material Contans. Somewhat lower but still significant disease control was achieved with Endura on plots infested with S. sclerotiorum. In this field trial, Endura provided the best level of disease control in plots infested with S. minor, whereas Contans provided the best level of disease control in plots infested with S. sclerotiorum.