Southeast Michigan vegetable regional report – July 2, 2014

Plant diseases have started to appear in various crops. The first corn earworm moths of the season were caught, indicating it is time to start insecticide applications in sweet corn fields with fresh silks.

July 2, 2014 - Author: Lina Rodriguez Salamanca, Michigan State University Extension


In the past week, rainfall recorded in the southeast averaged 0.5 inches. Air temperatures in the southeast have ranged from 55 to 86 degrees Fahrenheit. During the last week, five days had 10 or more humid hours during the day. Based on the average of the southeast Michigan Enviro-weather stations, we currently have reached 992 growing degree days (GDD) base 50 F with a maximum of 1,162 at the Petersburg Enviro-weather station.

Vegetable crops

Long periods of humidity have increased the incidence of soft rot in vine crop fruit, including zucchini yellow squash and cucumbers, and efforts were made to proactively harvest the fruit lying low to avoid fruit rot. Symptoms of angular leaf spot and anthracnose have been observed in vine crops, confirmation of the causal agent of the symptoms observed is ongoing. Wind speed continues to stress a variety of crops in the area, but also delaying protective spray applications.

Incomplete pollination has resulted in misshapen zucchini fruit. Pumpkin vines continue to develop while watermelon and muskmelon vines continue to expand and are bearing 5- to 8-inch fruit.

No significant influx of spores has been detected at the Monroe County cucurbit downy mildew traps. No cucurbit downy mildew has been detected at this time in the area. However, the epidemic continues in the southern states according to the Cucurbit Downy Mildew Epidemic Status Map. Continue to scout for cucurbit downy mildew symptoms and submit any suspicious symptoms to Michigan State University Extension educators or MSU Diagnostic Services as early detection is critical.

Sweet corn fields continue to develop with most fields likely to reach mid-silk by the end of the week. According to, no risk of corn earworms was forecasted for July 2, but three moths were caught in the Monroe County trap in the last week. It is time to consider insecticide applications in sweet corn fields with fresh silks.

No European corn borers have been caught at the Monroe County trap, and according to, low risk of western bean cutworms is forecasted for the southern part of the Lower Peninsula.

Peppers continue to develop with some fields starting to develop fruit. Tomato plants are bearing green fruit with some fresh market tomato fields showing foliar bacterial disease symptoms. Tomato harvest in the tunnels continues, while 5 percent incidence of gray mold symptoms in leaves and fruit has been observed.

Gray mold Gray mold
Gray mold in tomato fruit and foliage on hoophouses. Photo credit: Lina Rodriguez Salamanca, MSU Extension

Some potato fields have 1 to 2 percent incidence of symptoms that look like black leg and tuber soft rot, which is favored by the rain and high humidity periods from the last two weeks.

No symptoms of late blight in tomatoes or potatoes have been observed or reported in the area. The Michigan Late Blight Risk-Monitoring website forecasts moderate risk of disease development, with a total of 14 and six disease severity values (DSV) for the Petersburg Enviro-weather station and Romeo Enviro-weather station respectively. Continue to scout for late blight symptoms in potatoes and tomatoes as late blight was reported in Pennsylvania last week.

Cabbage, broccoli, kale and turnip harvest continues. Insect caterpillar management has been successful for most growers and population numbers remain low. Pea harvest is complete and snap beans and lima beans are filling pods and harvests have started.

For more information on commercial vegetable production, contact Lina Rodriguez Salamanca at 517-264-5310 or

Tags: agriculture, msu extension, organic agriculture, vegetables

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