Disease Note.

A Recent Outbreak of Lettuce Mosaic Potyvirus in Commercial Lettuce Production in Florida. R. N. Raid, University of Florida, Everglades Research and Education Center, Belle Glade 33430. R. T. Nagata, University of Florida, Everglades Research and Education Center, Belle Glade 33430; and L. G. Brown, Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Gainesville 32608. Plant Dis. 80:343. Accepted for publication 10 January 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0343C.

Small circular patches (approximately 3 to 5 m in diameter) of severely stunted lettuce {Lactuca sativa L.) were observed in a commercial production field of crisphead lettuce located near Belle Glade, FL, during early March, 1995. Additional symptoms included irregularly lobed leaves, down-turned leaf edges on more mature leaves, and an overall dull green appearance. Although mottling and mosaic were not observed, lettuce mosaic potyvirus (LMV) was suspected. The presence of LMV was confirmed using a double antibody sandwich enzyme-linked immunosorbent assay developed for assaying seed for LMV (1). A subsequent survey of all grower locations within the lettuce production region of south Florida revealed the presence of a large disease focus (approximately 2 ha in size) at the same farm location but approximately 1.5 km from the point of initial detection. Disease incidence was nearly 100% within (his focus, decreasing to 3 to 5% on the outer limits of a 1-km radius. Although LMV was detected at two other grower locations, both within 5 km of the aforementioned outbreak, incidence at these locations remained below 1%. Investigations were made with respect to possible primary inoculum sources for the outbreak. These implicate noncompli-ance with the lettuce mosaic virus certification rule (Rule 5B-38) of the Florida Department of Agriculture and Consumer Services, which stipulates that only seed lots certified as having 0 infected seed in 30,000 seeds tested be planted in a state-defined suppressive area, as the most likely cause for this epidemic. This is the first significant LMV outbreak detected in commercial lettuce production in Florida since the certification rule was implemented at grower request in May 1973, demonstrating the effectiveness of the seed certification program.