Jul 3, 2008

Downy Mildew Confirmed in Cucumbers in Michigan

A report from Michigan State University’s Mary Hausbeck:
On July 2, a technician from my lab detected downy mildew on cucumbers growing in Monroe County. This field was selected for scouting because it is where the spore trap is running. The infection is very light in this field and no fungicides had been applied. Based on the leaf samples, the infection is relatively recent. What I find to be worrisome is that all five spore traps in the state have now detected low levels of downy mildew spores in the air. With this field occurrence and recent storms, it is guaranteed that the spore counts will increase and outbreaks become more numerous.

I find it hard to believe that this outbreak in Monroe County is the only one in the state. Therefore, it is crucial that cucumber growers in the state begin their downy mildew spray program immediately! For the processing pickle growers who may have only recently planted, it is important to remember that young seedlings readily become infected with downy mildew. Seedlings that have their cotyledons infected with downy mildew create a miserable situation and must be avoided. Banded fungicide sprays over very young plantings can save a significant amount of money.

If you are growing other sorts of cucurbits such as pumpkins, zucchinis, gourds or squash, it is important to note that these crops are not as susceptible to downy mildew as cucumbers. Sprays for these crops can be delayed until downy mildew is noted in that particular county, as long as they are being scouted frequently. In past years, melons have become infected with downy mildew and should be treated with a protective fungicide program. For melons, the program can be a bit less intensive than the program recommended for cucumbers.