Phytophthora Blight: A Serious Threat to Cucurbit Industries.

Introduction Phytophthora blight, caused by the oomycete Phytophthora capsici, has become one of the most serious threats to production of cucurbits and peppers, both in the United States and worldwide (2,6,8,9,11,17,18,22,27,30). Phytophthora capsici was first described by Leonian on pepper in New Mexico in 1922 (20). In 1931, Tucker (38) classified it as a species of the genus Phytophthora and considered P. capsici as a host-specific fungus pathogenic on pepper. Subsequently, taxonomists (23,36,37) studied Phytophthora isolates from various hosts in the world and re-described the taxonomy of P. capsici. Recently, the incidence of Phytophthora blight on cucurbits has dramatically increased in Illinois (2,32) and other cucurbit-growing areas in the world (8,9,17,18), causing up to 100% yield loss. Cucurbit industries, particularly processing industries, are seriously threatened by heavy crop loss resulting from Phytophthora blight. For example, outbreaks of Phytophthora blight have threatened the processing pumpkin and other cucurbit industries in Illinois, where 90% of processing pumpkins produced in the US are grown (2,3) (Figs. 1 and 2). Similarly, the pickling cucumber industry of Michigan is jeopardized by the increased occurrence of Phytophthora blight (8). Because of heavy crop losses the growers often have to abandon their own farms for cucurbit production and move into different areas, sometimes traveling more than 50 miles, to find fields not infested with P. capsici.