Although the cucurbit growing season is winding down, we continue to see new outbreaks of downy mildew. We found downy mildew in pumpkins in our sentinel plot in Fremont, OH (Sandusky County) on Friday, September 12. Yesterday we found the disease in butternut squash in our sentinel plot in Celeryville, OH (Huron County). At this point growers need to decide whether or not fungicide application is a good idea from an economic standpoint. In southern Ohio, frost may occur for some time, so keeping cucurbit foliage protected from downy mildew with fungicides may be a good idea. Downy mildew affects leaves, not fruit, so if pumpkins or winter squash are ripe and curing in the field, it may not be necessary to apply fungicides to control the disease. However, control measures for powdery mildew and other diseases that affect handles or fruit need to continue. See my July 3, 2014 post for fungicide recommendations for downy mildew management.
For more information on cucurbit downy mildew and a map of outbreaks in Ohio and the US, see the Cucurbit Downy Mildew Forecasting website. The map below was captured today.
This is late blight weather – cool, rainy and overcast. Late blight is likely to be widespread in tomatoes in Ohio, especially in organic systems and gardens in which effective fungicides are not used. Yesterday we confirmed another outbreak of late blight in Summit County. See my posts for recommendations for late blight management in conventional and organic tomatoes.
We confirmed downy mildew in pumpkin leaves from Holmes County yesterday, and in zucchini from Guernsey County today. Cooler weather, overcast skies and rain or heavy dews are ideal for spread of downy mildew. Downy mildew fungicide recommendations are the same for squash and pumpkins as for cucumbers and melons. It is too late for the zucchini shown in the photo, but growers of winter and summer squash, pumpkins, cucumbers and melons should be on a fungicide schedule to protect their crops through the end of the season.
We confirmed late blight in tomatoes from a home garden in Wayne County, OH today. Rain and cool nighttime temperatures contributed to the outbreak. September is a risky month for late blight, so gardeners and commercial growers alike should continue scouting tomatoes and potatoes regularly. Management recommendations for late blight can be found in previous posts for organic and conventionally produced tomatoes.
Late blight lesion on a tomato leaf.