West central Michigan vegetable regional report – July 29, 2015
Warm weather has helped speed crop progress.
Asparagus disease severity value (DSV) accumulation for the last week ranged from 10-14 DSVs for three Michigan State University sensors during July 22-29. Warm nighttime temperatures likely contributed. Purple spot lesions were present on cladophylls in grower fields I visited this week.
Carrot growers should check aster leafhopper scouting reports this week as captures increased somewhat to our south in celery production areas.
Cucurbit downy mildew has been confirmed in 10 Michigan counties to date: Monroe, Gratiot, Allegan, Livingston, Tuscola, Macomb, Berrien, Midland, Bay, Isabella, Arenac, Ingham, Clinton and Saginaw. Zucchini harvest is ongoing in Oceana County this week, and pumpkins were forming fruit at one location I visited.
Onion growers should scout their fields for onion thrips given recent hot, dryer weather. A threshold of one thrips per leaf can be used for making decisions when applying all products except Radiant, which can be applied when populations reach three thrips per leaf.
Potato and tomato growers should be aware that late blight has been confirmed from a commercial potato planting in Montcalm County and in northern Indiana as well. Chlorothalonil-based products can continue to provide preventive protection for tomato growers. The late blight forecaster suggests weather could create a high risk of spread for three to five out of the next five days in west central and southwest Michigan through Aug. 3.
The insect forecaster for sweet corn predicts a low chance of a corn earworm flight today, July 29, but then very low risk of continued flights over the next five days. The western bean cutworm flight will likely peak this week. Egg masses were discovered in west Michigan field corn last week. Growers relying on transgenic control should note that only one trait – the Viptera trait – provides control of western bean cutworms. Weekly sprays applied for corn earworm should also take care of this pest. If you are not making sprays for corn earworm, scouting pre-tasseling corn for egg masses will be important. See the Michigan State University Extension fact sheet, “Managing western bean cutworm in field corn,” for more information. Note, experience suggests egg masses can be laid on the underside and top of leaves in sweet corn, which does not commonly happen in field corn.