Central Michigan vegetable update – July 25, 2018

Rain showers bring some relief to irrigation systems and non-irrigated crops.

Weather

Welcomed rain showers were received over the past weekend with most areas receiving 0.5 to 2 inches of rainfall. Air temperatures have moderated with highs in the 70s up to the lower to mid-80s for much of the period. This has reduced potential evapotranspiration rates. A few market gardens that rely on surface water sources have had some difficulties with irrigation ponds running dry.

Crops

Sweet corn harvest is beginning. Western bean cutworm flight is peaking this week. So far, egg mass production appears relatively low with many egg masses having a relatively small number of eggs; however, scouting is still warranted as it only takes a few viable larvae to reduce sweet corn quality. Second generation European corn borer flight is beginning to pick up. This pest will likely peak in early August in central Michigan.

Potato growth continues with tubers sizing. Disease pressure has been relatively low with no reports of late blight from scouts. Variegated cutworm continues to be observed in low to moderate numbers in potato fields.

Scout pickling cucumbers closely this week for downy mildew. While there are no reports of downy mildew in the central region, downy mildew has been identified in Berrien County in southwest Michigan. Consider beginning a downy mildew spray program.

Pea harvest is winding down with a few fresh market peas yet to be harvested.

Dry beans continue flowering and setting pods. Continue monitoring for potato leafhopper as well as tarnish plant bug, as protection from seed treatments begins to wain in the coming weeks.

Summer squash harvest of continues. Powdery mildew is appearing on many older plantings.

Several calls have been received this week concerning giant hogweed. I have not yet identified giant hogweed, or a good suspect, from any of the pictures sent to me or from what growers have showed me. Giant hogweed is a poisonous plant and workers should avoid contact with suspected hogweed plants. Michigan State University Diagnostic Services can help you identify this weed—send photos or inquiries to pestid@msu.edu.

Insects

Continue monitoring for thrips and twospotted spider mites in the coming weeks as dry weather returns. Also monitor for potato leafhoppers, tarnished plant bugs and other Hemipteran pests, as succulent, irrigated vegetable crops may become very attractive as the alternate host plants in the surrounding landscape dry down.

True armyworm outbreaks in the north appear to be ending as larvae are pupating. It is still possible, however, to find feeding populations, as this migratory pest can still appear in the region.


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