Cucurbit downy mildew (CDM) is being reported on cucumbers, butternut squash and now pumpkins across the state of Virginia.
To keep track of where downy mildew has been reported please visit the following website: http://cdm.ipmpipe.org/.
During the past week, we have received several reports of downy mildew on pumpkins, one of the important cucurbit crops in the state.
Cucurbit growers are urged to consider spraying preventative applications for downy mildew and thoroughly scout for the disease. Growers are strongly recommended to initiate a downy mildew protection program.
Over the past growing seasons, our research has found spray programs containing Ranman (2.75 floz/A) to offer the best protection from this disease. Presidio (4 floz/A) and Previcur Flex (1.2 pt/A) are also effective.
However, we caution growers not to rely upon these materials solely as our trial results from 2009-2012 for Previcur Flex and 2011 and 2012 for Presidio were not as favorable as in past seasons in our cucumber CDM trials.
Previcur Flex and Presidio have performed better in our pumpkin and other cucurbit trials than in our cucumber trials. These materials should be rotated/tank-mixed with protectant fungicides containing mancozeb or chlorothalonil.
Fungicide applications should be initiated prior to disease development and applied on a 7-10 day schedule.
Growers will realize optimal disease control when applications are made in at least 20 GPA of water and crop coverage is good.
Cultural practices, such as avoiding low lying fields and excessive overhead irrigation, will also suppress disease development.
There are some differences in the susceptibility of cucumber cultivars to CDM. If you have any questions along those lines, please feel free to contact us.
Cucurbit downy mildew can be recognized initially by small yellow spots on the upper surface of the lower leaves. When humidity is high (particularly early in the morning) blue/gray sporulation can be found on the underside of the leaves.
If you have any further questions or think you have cucurbit downy mildew present in your field, please let us know. We will continue to update you on the progress of this disease.
Contact me at [email protected] or call 757-414-0724; ext. 17.