The Michigan State University Vegetable Pathology Lab teams up with Michigan State Extension to publish vegetable updates throughout the growing season. View the July 31 update here.
Southeast Michigan vegetable update
In pumpkins and winter squash, downy mildew has been found on hard squash in Pennsylvania and Tennessee. Downy mildew is a complex disease with many strains. We see a strain that impacts cucumbers and melons every year in Michigan, while the strain that impacts pumpkins and winter squash is much less common here.
Southwest Michigan vegetable update
Vine crop producers need to be diligent in their downy and powdery mildew control. Downy mildew was first observed July 28 and we have had good weather for spread, especially on Aug. 6 (cool and wet). Current control recommendations, observance maps and spore counts can be found at MSU Downy Mildew News. Vine crop fields should also be removed soon after last harvest so they cannot serve as an inoculum source for remaining plantings. This is when powdery mildew also begins to show up.
East Michigan vegetable update
Pickling cucumber yields have been down and the size classes have been split. This means some environmental condition caused some flowers to abort and split the fruit set between two flowering periods. Downy mildew has not been found yet in Thumb and Bay areas, but it has been found in Berrien County. Protectant sprays are a good idea.
Melons are being harvested, but watermelons are still lagging behind. Summer squash harvest is ongoing. Fruit quality is excellent for these crops.
Pumpkins and winter squash are in various stages of progress. Some are in full bloom and vining and others are still just starting to vine. Still, others appeared to stress flower without vining at all.
West central Michigan vegetable update
For cucurbits, downy mildew was detected in Berrien County on July 29. Pickle and melon growers should include a downy-specific material in their spray program.
Cucurbit powdery mildew colonies increased over the past two weeks at one pumpkin field. Powdery-specific fungicides should be applied on a regular (seven-to-10 days) schedule as labels permit where protection is needed. Check out page 128 of the Midwest Vegetable Production Guide for information on products.
Phytophthora capsici was causing root, crown and fruit rot in Oceana County cucurbits last week after recent heavy rains.
For winter squash, remember that protection of acorn, butternut, spaghetti and Buckskin fruit is most critical for the first 21 days after fruit set. After this, fruit develop a degree of age-related resistance.