West central Michigan vegetable regional report – July 22, 2015

Conditions were ripe for development of foliar diseases over the weekend in west Michigan.

Heavy dews that last late into the morning, warm overnight temperatures and early morning temperatures can hasten development of purple spot disease of asparagus.

Heavy dews that last late into the morning, warm overnight temperatures and early morning temperatures can hasten development of purple spot disease of asparagus.

Crops

Asparagus beetle eggs, larvae and adults plus Japanese beetle adults were present in asparagus fields I visited this week. Damage due to Japanese beetle feeding was visible in one location this week. Warm, humid weather and rain over the weekend led to high disease severity value (DSV) accumulation, suggesting conditions were favorable for purple spot development. The TomCast disease forecasting system can be used to time fungicide sprays for purple spot.

Carrot fields should be scouted for foliar diseases as conditions in west Michigan over the weekend were favorable for disease development.

Cucurbit downy mildew has been confirmed in seven Michigan counties to date: Monroe, Gratiot, Allegan, Livingston, Tuscola, Macomb and Van Buren. Potential bacterial disease has been noted in west Michigan cucurbits this growing season, and was visible July 22 in zucchini plantings. Note that bacterial diseases of cucurbits are often seedborne. Copper materials are the main tool available for these diseases, but need to be applied on a seven-day schedule to be maximally effective.

Onion downy mildew has been observed in some growing areas of Michigan.

Potato and tomato late blight risk is forecast to be high for three to four out of the next five days at most west Michigan locations. The presence of late blight was confirmed in western Ontario tomatoes on July 14. This disease has not been confirmed in Michigan to date. Conditions for early blight were good over the last weekend. Growers have struggled with glyphosate damage in tomatoes this spring. Damage can still occur even with shielded applications made between raised beds.

Sweet corn insect trap data are below. Western bean cutworm numbers increased this week in one Oceana County location. Pre-tasseling fields are most attractive to egglaying females of this pest. Once trap catches indicate adult activity, scouting should focus on egg masses. To scout for these, check the upper surface of the top three to four leaves of 20 plants at five locations. For more information, see “Scouting corn for western bean cutworms” from Michigan State University Extension.

Sweet corn insect trap data

Location

Pest

July 9

July 16

July 22

Oceana 1

Corn earworm

1

0

5

Oceana 1

Western bean cutworm

1

12

13

Oceana 2

European corn borer

0

0

0

Oceana 2

Western bean cutworm

0

6

38

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