Southeast Michigan vegetables regional report – July 24, 2013

Be proactive with fungicide programs in vegetable crops. The weather has been conducive to disease that if unmanaged, can greatly impact target yield quantity and quality.


Temperatures in the southeast ranged from 62 to 93 degrees Fahrenheit with an average of 78 F. In the following week, temperatures are forecasted to range from 53 to 83 F. Several scattered precipitation events were observed and recorded 2 inches of rain. The next precipitation events are forecasted for Saturday and Sunday (July 27-28). Humidity levels continue to be high (37 to 93 percent relative humidity) with duration of humidity from 10 to 24 hours.

Current growing degree days (GDD) recorded at the Petersburg Enviro-weather station are 2,308, 2,010 and 1,546 (GDD base 42, 45 and 50 F respectively), and are behind the five-year average by 113.2, 82.8 and 46.3 (GDD base 42, 45 and 50 F respectively).

Vegetable crops report

Cabbage harvest continues and transplants for the fall will soon be planted, but growers are waiting for favorable soil conditions and avoid the excessive soil moisture. Table beets with Cercospora leaf spot and pepper bacterial spot have been observed. In previous years, including 2013, the weather was not as conducive to disease compared to this year. Remember to protect crops new growth with fungicide application. In cases like bacterial spot in peppers, if the disease is not managed properly, symptoms can be visible on pepper fruit or the plants can suffer severe defoliation that make the pepper fruit prone to sunscald.

Squash vine borers are active. Three moths (Photos 1-2) were trapped in the Monroe County trap. Damage and small larvae (one-fifth of inch) have been observed. Adult squash vine borer flight will be completed in 435 GDD (base 50 F) when we reach 2,024 GDD (base 50 F). Scout your fields for frass, wilted vines, larvae point of entry and larvae inside the crown of wilted vines. For labeled insecticides and rates, consult the Michigan State University Extension E312 bulletin “2013 Insect, Disease and Nematode Control for Commercial Vegetables.” Always read insecticide labels.

Squash vine borer Squash vine borer
Photos 1-2. Squash vine borer adults caught in the Monroe trap. Photo credit: Lina Rodriguez-Salamanca, MSU Extension

Harvest continues for cucumbers, squash and zucchini. The harvest will begin in a couple weeks for melons and cantaloupes. Powdery mildew symptoms have been observed in zucchini and pumpkins. Cucurbit downy mildew epidemic continues in the southeast of the state with a new report in Monroe County. See information on how to recognize downy mildew symptoms and instructions on how to submit samples. Scout your cucurbit fields (cucumbers, zucchinis, squash, pumpkins, melons and gourds) for symptoms and protect new growth following fungicides recommendations.

Late blight risk in our area has accumulated 17 disease severity values (DSV), and has been reported in north Ohio. To get a more accurate DSV for your field, visit the Late Blight Risk Monitoring website and enter the day of emergence. Fungicide recommendations from last week still stand (highest labeled rate of protectant fungicide is recommended in a minimum of seven-day intervals). Potato and tomato early blight symptoms have been observed in several fields. Colorado potato beetle populations have increased in the last week.

Sweet corn harvest has begun. Western bean cutworm moth count was low (one moth caught in seven days) in the Monroe County trap this week and no egg masses have been observed. The risk for this insect pest continues to be forecasted as moderate in our area.

Corn earworm moths were low and below threshold this week; only three moths were caught in 10 days in both the Monroe and Lenawee county traps, however protecting fresh silks with an insecticide application is important to minimize ear damage. No European corn borers have been caught in the Monroe County trap.

Remember that food safety also includes physical and chemical risk and not only biological. Check out MSU Extension educator Phil Tocco’s most recent article on risk types when developing a food safety plan.

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