West central Michigan vegetable regional report – August 19, 2015

Late-season diseases and insect pests are present in west Michigan vegetables.


Asparagus disease management is the current focus in the growing region. Recent warm nights have been favorable for development of purple spot disease in asparagus.

Cole crop pests including cabbage looper were present in Oceana County this week.

Cucurbit downy mildew was detected in Mason County late last week in cucumbers, and was also detected in Ottawa County. Cucumber and melon growers in these regions typically do not face pressure from this pathogen, but may face losses this year if plantings are not protected. See Michigan State University Extension plant pathologist Mary Hausbeck’s example spray program against downy mildew.

Powdery mildew continues to be present in our growing region. Phytophthora capsici has also been causing plant death in low spots in some areas of west Michigan. Aphid activity has picked up to our south, so be on the lookout for virus symptoms.

Potato and tomato growers should be aware that late blight was detected in Michigan tomatoes over the last week. If it is present on your farm or in your county, consider switching to fungicides that target the oomycetes, a group of pathogens that include applying chlorothalonil-based products on a weekly schedule before late blight is detected. The Michigan Late Blight Risk Monitoring suggests weather could create a high risk of spread for three to four days out of the next five days in west central and southwest Michigan through Aug. 16.

Sweet corn growers should check their corn earworm traps today. Cooperators have reported trap catches suggesting there may have been a larger flight overnight. If you capture more than 50 moths per night, consider tightening your spray interval to three days. Western bean cutworm numbers declined at two locations over the last week, suggesting peak flight is past for this pest. 

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