Cooler and drier weather has contributed to fruit development. Western bean cutworm moth catch is high, while low to no corn earworm activity has been observed. Thrips are slowly moving into peppers and cabbage.
Posted on July 23, 2014 by Lina Rodriguez Salamanca, Michigan State University Extension
Powdery mildew in yellow squash. Photo credit: Lina Rodriguez Salamanca, MSU Extension
Weather
In the last two weeks, drier weather has been predominant, with only 0.34 inches of rainfall recorded at the Michigan State University Petersburg Enviro-weather station, while the Commerce Township Enviro-weather station recorded 1.17 inches. The average for the southeast station was 0.63 inches.
Air temperatures in the southeast have ranged from 48 to 87 degrees Fahrenheit, with mostly cloudy days. Up to 15 humid hours were recorded at the Petersburg Enviro-weather station in the last week. Based on the average of the southeast Enviro-weather stations, we currently have reached 1,370 growing degree days (GDD) base 50 F.
Temperatures are forecasted to range from 52 to 86 F over the next week with low chances of rain, ranging from 9 to 14 percent, Thursday and Friday, July 24-25, and increase chances of rain, more than 30 percent, for Saturday to Monday, July 26 -28.
Harvest of cole crops and transplanting of fall cole crops continues. Caterpillars (loopers, imported cabbage worms and diamondbacks) continue to be active, but in very low numbers. Due to the dry weather experienced in the area, thrips are slowly moving into cabbage fields, especially onto fields with no irrigation. To manage thrips in cabbage, scout for thrips and remember that when insecticide application is necessary, the treatment is more efficacious prior to head formation.
Harvest of cucumber, zucchini and yellow squash continues and will come to an end soon. Vine crop insect populations remain low. Management of cucumber beetles has been successful, and no major squash vine borer damage or squash bug populations have been observed at this time.
Powdery mildew has made its appearance in southeast Michigan; initial symptoms have been spotted in squash (see photo) and watermelon vines. Michigan State University Extension advises that effective powdery mildew management requires a combination of resistant varieties and appropriate alternation of fungicides with different FRAC groups to avoid resistance build up. Fungicides with high risk of resistance are in FRAC groups 1 and 11 among others.
Michigan State University vegetable pathology specialist Mary Hausbeck confirmed cucurbit downy mildew is in Michigan. Even though the influx of spore in the Monroe County trap is less compared to the Bay and Saginaw, Michigan spore traps, growers are advised to protect vine crops following Hausbeck’s recommendations.
Pumpkin fruit set benefitted from the cooler weather, and pumpkin fields are bearing - to 12-inch fruit. Symptoms of angular leaf spot continue to be observed in several pumpkin fields, while incidence of powdery mildew is very low at this time. Similarly, melons (watermelon and muskmelons) are bearing fruit with no major disease or insect problems at this time.
Pepper fruit development continues. Banana peppers are 6 to 10 inches long, jalapenos are 3 to 5 inches long, and bell peppers are 3 to 4 inches long. Continue scouting for thrips. Very low numbers of thrips have been observed, but the population may increase due to the warm and dry weather.
Fresh market tomato harvest continues in tunnels and field harvest will begin soon. Processing tomato fruits have started to ripen. Late blight was confirmed on potatoes in Michigan. Protect your tomatoes from late blight by following Hausbeck’s recommendations. For potatoes, visit www.cnchemicals.com/ to get a recommendation based on your location and planting date. Also, make sure to read MSU plant pathologist Willie Kirk’s article “Fungicides for late blight control in potatoes.”
Sweet corn harvest has begun. No corn earworm moths were caught in the last seven days in the Monroe County traps, and low risk continues to be forecasted for the area. However, 28 western bean cutworm moths were caught in the last five days in the Monroe County trap. No egg masses have been observed, and the risk for this insect pest continues to be forecasted as moderate to high in our area, according to www.cnchemicals.com/. No European corn borer moths have been caught in the Monroe traps this week.
For more information on commercial vegetable production, contact Lina Rodriguez Salamanca at 517-264-5310 or .(JavaScript must be enabled to view this email address).
This article was published by Michigan State University Extension. For more information, visit http://www.cnchemicals.com/. To contact an expert in your area, visit http://www.cnchemicals.com/, or call 888-MSUE4MI (888-678-3464).
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