![]() ![]() high humidity/rainfall) thousands of sporangia develop, which then disperse in wind currents and can be transported hundreds of miles. Under correct environmental conditions (i.e. Often, both diseases can be seen simultaneously. Signs include a white ‘powder’ that covers the upper leaf surfaces. Powdery mildew is a common fungal disease that is also found on cucurbit leaves. The name ‘downy’ is attributed to the development of gray spores called sporangia that result in a fuzzy or downy appearance on lesions located on the underside of leaves. Individual infected cucumber plants (cucumbers are very susceptible to this pathogen) A close-up view of the undersurface of a chlorotic lesion with accompanying sporangia giving it a ‘downy’ appearance Individual sporangia clusters SymptomsĬucurbit downy mildew is easily recognized by its characteristic mosaic pattern of chlorosis and necrosis (dead cells) on the upper surfaces of cucurbit leaves, but leaf symptoms vary between cucurbit species. This prevents the sporangia from overwintering in the frost-prone northern states. It should be noted however, that spores can survive 1-2 weeks and they are dispersed by wind, which facilitates the survival of the cucurbit downy mildew pathogen in states with warmer winters or in greenhouses. As a result, the asexual sporangia are unable to remain viable over long periods of time. Downy mildew is a water mold and an obligate parasite. cubensis results in defoliation, poor plant health, and significantly reduced fruit yields due to sun scald, reduced nutrition, and secondary rots. Cucurbit downy mildew in a cucumber field with many necrotic and chlorotic lesions Causal Agent Substantial losses in yield occur if appropriate management strategies are not in place. Symptoms of the disease include a characteristic mosaic pattern of chlorosis and necrosis found on the upper surfaces of leaves. It has a wide host range as the pathogen can infect over 60 different hosts, including cucurbits such as cantaloupe, cucumber, watermelon, squash, and pumpkin. It is caused by Pseudoperonospora cubensis, which is an oomycete pathogen, otherwise known as a water mold. ![]() Cucurbit downy mildew can cause severe losses. IntroductionĬucurbit downy mildew is a devastating disease in central and eastern United States as well as globally. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |