2009 Annual Meeting Abstract of Special Session Presentation

Plant Disease Management
Cucurbit Downy Mildew: Re-Emergence of a Historical Disease

The history and re-emergence of cucurbit downy mildew
G. HOLMES (1), C. Thomas (2)
(1) Valent USA Corporation, Cary, NC; (2) USDA ARS (retired), Charleston, SC
Phytopathology 99:S171

Cucurbit downy mildew (DM), caused by Pseudoperonospora cubensis, was first described in 1868 in Cuba. It is among the most well-known downy mildew diseases in the world, attacking cucurbits wherever they are grown, especially in humid climates. It is also one of the most notorious pathogens for developing resistance to fungicides. Several research programs in Israel, the U.S.A., Japan, India and the Czech Republic have contributed to an extensive knowledge-base currently in place. Breeding efforts in cucumber in the 1950s and 60s led to the development of resistance levels sufficient to control the disease without the use of fungicides. Although this resistance was not as effective in other parts of the world, the U.S. enjoyed approximately 35 years of effective control against the disease. This changed in 2004 when the cucumber crops from North Carolina to New Jersey and beyond were destroyed by DM. The disease is now a major problem on cucurbits throughout much of the eastern half of the U.S., especially on cucumber. This led to the re-establishment of cucumber breeding efforts for DM resistance as well as research programs in pathogen biology and epidemiology. These programs are approaching an old problem using new tools.