Evaluation of Products to Manage Sclerotinia Drop of Lettuce in 2004

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 2003-2004. 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, all materials tested at an appropriate rate significantly reduced disease. In plots infested with S. minor, the best treatments included Endura, Fluazinam, and Contans alternated with Endura. For plots containing S. sclerotiorum, the best treatments included Fluazinam, Contans, Switch, Endura, and Contans alternated with Endura. Two of the products tested, Contans and Serenade, are biological control materials. 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 a true picture of the relative efficacy of tested compounds for control of Sclerotinia drop.