Establishing and Maintaining a Lettuce Drop Nursery. J. L. Troutman, Associate Research Scientist, Department of Plant Pathology, University of Arizona, Yuma 85364. J. C. Matejka, Research Assistant, Department of Plant Pathology, University of Arizona, Yuma 85364. Plant Dis. 66:415. Accepted for publication 22 September 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-415.

Lettuce drop, caused by Sclerotinia sclerotiorum, is a destructive, sporadic disease in Arizona. Because natural infection is unreliable for chemical control work, a procedure was developed for establishing a lettuce drop nursery. Sclerotia harvested from a barley grain medium were dried and incorporated into lettuce beds that had been thinned at a predetermined rate. The optimal time for studying chemical efficacy for controlling lettuce drop is during January, February, and March, when air temperatures range from 0 to 20 C. For the past 4 yr, this program has been very successful for determining the efficacy of various fungicides for controlling lettuce drop.

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