Comparative Evaluation of Products to Manage Sclerotinia Drop of Lettuce in 2005

Abstract

Sclerotinia drop on lettuce is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperatures favor this disease. Some registered products as well as new chemistries in development were compared for their ability to suppress Sclerotinia drop on lettuce during the winter vegetable growing season in 2004-2005. Sclerotia of each pathogen were incorporated into plots after lettuce thinning and just before the first application of test compounds. In plots infested with either Sclerotinia minor or S. sclerotiorum, most materials tested at an appropriate rate significantly reduced disease. In plots infested with S. minor, the best treatments included Endura, Endura followed by Rovral, Botran, and Endura + Contans. For plots containing S. sclerotiorum, the best treatments included Endura + Contans, Endura followed by Rovral, and Contans. One of the products tested, Contans, is a biological control material. For a valid comparison of products for control of Sclerotinia drop of lettuce, it is important to compare the results obtained from more than one field study. The reader is urged to review previous studies in addition to this report to get an accurate picture of the relative efficacy of tested compounds for control of Sclerotinia drop.