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AgAlert! Cucumber Downy Mildew and Anthracnose

Take preventative measures before these foliar diseases affect your cucumber harvest

Cucumber downy mildew (CDM) has now been reported from neighboring states (Virginia, Pennsylvania, Ohio and Kentucky). It is predicted that the disease can be in West Virginia, especially in the counties bordering other states, within a few days (https://cdm.ipmpipe.org/). 

This is the best time to take preventative measures against this deadly disease. If cucumber plants are treated with either mancozeb (Manzate, Dithane, Penncozeb, Fore, Roper, etc.) or chlorothalonil (Bravo, Daconil, Fungonil, etc.) on a weekly basis prior to the arrival of the pathogen in your area, it can be effective in delaying the onset of the disease or completely preventing infections.

However, another foliar disease called anthracnose is more prevalent this year compared to previous years. Thus, it is important to understand the difference of the disease symptoms and treat plants accordingly. Symptoms of downy mildew (top) and anthracnose (bottom) are shown here. 

Cucurbit downy mildew on a leaf. cucumber anthracnose on leaf.

Cucumber downy mildew (CDM) symptoms show angular chlorotic lesions (top), while anthracnose shows roundish lesions with a shot-hole appearance due to drop of tissues from the centers of lesions (bottom).

This alert impacts all West Virginia counties. West Virginia counties bordering other states should take extra precaution, but any cucurbit crop grown in any county should be scouted carefully at this time and take preventative measures.

Please send suspected samples to WVU Plant Diagnostic Clinic.

Get help from the WVU Plant Diagnostic Clinic

Contact

Mahfuz Rahman
WVU Extension Specialist
Plant Disease Specialist
304-293-8838
Email Mahfuz

Trade or brand names used in this publication are for educational purposes only. The use of such product names does not imply endorsement by the WVU Extension Service to the exclusion of other products that may be equally suitable.