Southeast Michigan vegetable regional report – August 29, 2012

Harvest continues in sweet corn, tomatoes and cucurbit crops. Be on the lookout for late blight in tomatoes, cucurbit downy mildew and cabbage downy mildew.

Weather

We had 6/10 of an inch of rain on August 27 (only one rain event). We had a combination of cooler weather and hot days in the weekend. Temperatures have averaged in the mid-70s with a minimum of 47 F to a maximum of 93 F. Humidity has ranged from 24 to 94 percent with nine to 18 hours of wetness.

Crops and pests

Most sweet corn harvest is completed and the later planted sweet corn will be wrapping up soon. In the Monroe County trap, 81 corn earworm moths were caught on August 27. Monitoring will continue for an additional week.

As processing and fresh market tomato harvest continues in the southeast, keep in mind that despite the fact that there are no reports of late blight in southeast Michigan, the closest report was in Ontario, Canada, on August 20 in tomatoes. This disease is wind-borne and if you want to keep your tomatoes longer, scout your fields for symptoms and review the late blight management tools.

Late blight
Late blight on tomato leaf. Photo credit: Lina Rodriguez-Salamanca, MSUE

View photos of other disease symptoms in tomatoes that are NOT late blight.

Tomatoes in tunnels have leaf mold incidence, some white fly populations and virus (most likely tomato yellow leaf curl virus).

Cucurbit crop harvest has slowed down, but continues. Currently, the forecasted risk for cucurbit downy mildew remains moderate for our area. In Michigan, 10 counties have confirmed reports of cucurbit downy mildew. Scout your fields and keep up with the recommended spray program for your crop.

Pumpkin growers are challenged to keep their vines protected from powdery mildew. Keep in mind there have been reports of powdery mildew resistance to fungicides. Use product rotation in a weekly basis with products that belong to a different fungicide group. For example, use Quinoxyfen and chlorothalonil (tank-mixed) in one week, followed by pyraclostrobin the next. If you have planted pumpkins on a field with a history of Phytophthora rot, the Managing Phytophthora on Winter Squash and Pumpkin bulletin will provide you with management strategies.

Transplant of brassica crops (cabbage, broccoli, cauliflower, etc.) for the fall has started and some fields have been established for a week or two. With thrips causing a lot of damage in cabbage, scout your field for thrips and other insects. The management tools will be more effective the earlier you detect them.

Earlier in the year we had a cabbage downy mildew report. Keep in mind the disease symptoms as cool temperature and long dew period favor the disease.

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