Occurrence and control of downy mildew of netted melon in Chonnam province.
Downy mildew (Pseudoperonospora cubensis) of netted melon broke out in 1996 in Chonnam province, Korea Republic, following cool and humid weather during mid Jun. to mid Jul. and low temp. and frequent precipitation. Large, irregular lesions and small necrotic polygonal lesions appeared on the lower leaves, developing onto the upper leaves of downy mildew-infected netted melon plants during the flowering season, resulting in death of whole leaves. Disease severities ranged from 1-100% in 12 greenhouses at Damyang, Chonnam province. In a severe case, the disease devastated the whole plantation, which made it impossible to harvest melons. Fungicides were sprayed 3 to 8 times to control the disease, but the control was not successful probably because of failure to detect the disease early enough and in the selection of inappropriate fungicides. Overuse and/or misuse of fungicides was a serious problem in disease control.