Southeast Michigan vegetables regional report – July 17, 2013

Cucurbit downy mildew has been reported and confirmed in Monroe and Lenawee Counties. Scout regularly and tighten the interval of your fungicide applications to minimize yield reductions.


Temperatures in the southeast ranged from 54 to 90 degrees Fahrenheit with an average of 72 F. In the following week, temperatures are forecast to range from 56 to 91 F. The last rain event in our area was July 10. The next precipitation events are forecast for Friday and Saturday.

Current degree-days (GDD) recorded at the Petersburg Enviro-weather station are 2067, 1789 and 1360 (BDD base 42, 45 and 50 F respectively), and are behind the 5 year average by 133.4, 103.4 and 63.2 (BDD base 42, 45 and 50 F respectively).

Vegetable crops report

Water standing in low areas of fields has drained and evaporated. However, patches of chlorotic or dead plants are the common denominator across vegetable fields with areas that were flooded earlier, especially cabbage, tomato and peppers.

Rain damage in pepper field
This southeast Michigan pepper field is showing damage from frequent
rain events. Photo credit: Lina Rodriguez-Salamanca, MSU Extension

Cabbage harvest continues and is almost complete. Cabbage fields have had an increased incidence of soft rot and plant death.

Damage in cabbage field
A cabbage field affected by recent rain events.
Photo credit: Lina Rodriguez-Salamanca, MSU Extension

Harvest has started and will continue for cucumbers, squash and zucchini. Melons and cantaloupe plants are bearing fruits 6 to 9 inches in diameter. Processing and Jack o’ Lantern pumpkin plants are bearing green fruit 2 to 5 inch in diameter.

Cucurbit downy mildew was reported and confirmed in cucumber fields in Lenawee and Monroe counties (see photo). For information on how to recognize symptoms visit the Hausbeck lab’s page on downy mildew on cucumber or see how to submit samples for instructions to send in samples. Scout your cucurbit fields (cucumber, zucchini, squash, pumpkin, melons and gourds) for symptoms and protect new growth following fungicides recommendations.

Downy mildew on cucumber Downy mildew on cucumber
Cucurbit downy mildew in Monroe and Lenawee County cucumber fields.
Photo credits: Lina Rodriguez-Salamanca, MSU Extension

Powdery mildew has been observed in squash and zucchini (see photo). Consider spraying fungicide on the groups quinolones and benzamidoxime (for example Quintec and Torino respectively) in rotation with other labeled fungicide that belong to different FRAC codes. Always read the fungicide labels to take into account the fungicide group (FRAC code) and appropriate rates and restrictions. Symptoms of Phytophthora root rots were observed on watermelon (to be confirmed).

Powdery mildew
Powdery mildew on zucchini foliage. Photo credit: Lina Rodriguez-Salamanca, MSU Extension

Late blight has been confirmed in potatoes in Michigan. The risk of late blight at the Petersburg station has accumulated 24 disease severity values (DSV) in our area. Fungicide recommendation from last week still stand (highest labeled rate of protectant fungicide is recommended in a minimum of 7-day interval).

Tomatoes are bearing green fruit 1.5 to 3 inches in diameter. Symptoms of bacterial speck have been observed in tomato foliage. Symptoms of early blight (Alternatia solani) and Septoria leaf spot are also common in tomato plants. Fungicide programs that include labeled protectant fungicide (Chlorotalonil products- for example Bravo) mixed or alternated with translaminar QoI-Strobilirin fungicide (for example Azoxytrobin-Quadris) is recommended. For more fungicides labeled and their rates consult the Michigan State University Extension publication E312 “2013 Insect, Disease and Nematode Control for Commercial Vegetables”.With late blight confirmed in the state, protect your tomatoes following Dr. Mary Hausbeck’s recommendations.

Tomato hornworms are present in tomato fields. Banana, jalapenos and bell peppers are bearing fruit 3 to 5 inches long. No thrips have been observed in peppers, however with the hot weather and lack of precipitation of the past week, thrips and other insect population can peak quickly.

Growers estimate that 10 to 20 percent losses in both tomato and peppers due to the flooded areas and hail damage experience early in the month.

Sweet corn harvest will begin this week. Western bean cutworm moths are active, 10 moths were caught in the Monroe trap this week, no egg masses have been observed. The risk for this insect pest is forecast as moderate in our area.

Corn earworms moths were caught in both Monroe and Lenawee county traps. Currently both counts are above threshold and insecticide sprays to protect fresh silks are recommended. No European corn borer has been caught in the Monroe trap. This is also good news for peppers and tomatoes since this insect pest can feed on pepper and tomato fruit.

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