Southeast Michigan vegetable update – July 18, 2018

It is quite dry. Irrigation systems are working overtime and insect pests are active, but disease development is being hampered.


It is hot and dry. Potential evaporation rates have been high and soils are dried out. Monday night, July 16, brought sporadic rainfall with some areas getting up to half an inch while other areas got little or none. The next best chance of rain comes this Friday, July 20, and into the weekend, with 0.5-1 inch predicted across the state. For the remainder of the month, climate models are calling for normal to below normal temperatures, so the pleasant weather of the last few days may continue.

The table below presents rainfall (in inches) for the Michigan State University Enviroweather stations in southeast Michigan, as well as growing degree-days (GDD) calculated using the Baskerville-Emin Method. Degree-day average for Commerce and Hudson is over five years, while Deerfield is over two years. Rainfall is in inches, with parenthesis indicating precipitation accumulations since last week’s report.

Rainfall and GDD totals as of July 18


GDD (base 42)

GDD (base 50)

5-year GDD average (base 50)

Rainfall since April 1





10.65 (+1.43)





9.93 (+0.01)





12.43 (+0.08)


MSU Extension entomologist Zsofia Szendrei reports getting many calls about thrips in all kinds of vegetables this week. With the hot weather and hay harvest, thrips are moving into vegetables, though this cooler weather will hopefully alleviate things. For more information about thrips, see her article, “Hot, dry weather increases risk of spider mites and thrips in field-grown vegetables.”


Cole crop harvest (all except Brussel sprouts) and planting continues. The dry weather has drawn thrips into some fields, and diamondback moth and imported cabbage worm are feeding. Cabbage loopers are being reported in higher numbers on organic farms.

In cucumbers, harvest of pickling and slicing cucumber continues. Downy mildew still hasn’t been reported in our region. MSU Extension plant pathologist Mary Hausbeck’s 2018 recommendations can be found in her article, “time for downy mildew protectant crop sprays in cucumbers.”

In cucurbits, squash bugs are active. I’m still catching squash vine borer in my Washtenaw County trap; I have caught none in my Lenawee County trap to date. There have been reports of powdery mildew in summer squash fields in southwest Michigan that are no longer being harvested or managed, but haven’t been pulled out yet.

Sweet corn harvest has begun. Corn earworm catches have been minimal. The next predicted time for flight according to Insect Forecast will come late this week.

Western bean cutworm catches tripled this week in my traps in Lenawee (17), Monroe (31) and Washtenaw (24) counties, though we still haven’t reached peak flight yet. Scout pre-tassel corn for egg masses—even Bt corn. The only Bt strain available with activity against western bean cutworm is VIP3A, which is currently only available in Syngenta varieties with the Attribute II package (Aspire, Remedy, Protector). If your Bt corn doesn’t contain the VIP3A protein, treat it like non-traited corn for the purposes of western bean cutworm control.

Many of the fields I’ve been in have no western bean cutworm eggs, but lots of natural enemies. You can save money and let the beneficials do the work for you, depending on what you find. The current fresh market sweet corn treatment threshold is 1 percent of plants with eggs or small larvae present. Pyrethroid chemistries can be used; get the first treatment on as silks emerge. For organic production, Bt is an option.

If there is an intensive corn earworm control program in place (weekly sprays), this should keep western bean cutworm at bay from here on out, but if the corn earworm program is more lax, intervals may need to be tightened.

Tomatoes are being harvested from hoop houses. The late blight forecaster is still suggesting medium late blight risk for tomatoes and potatoes at all MSU Enviroweather stations in our region. There hasn’t been a recent late blight report in the eastern U.S.

I have been trapping for brown marmorated stink bug in tomatoes in Washtenaw and Lenawee counties; traps catches have been minimal. Tomato hornworm is out and feeding.

Contact me any time at 517-264-5309 or with pest identification requests and questions. I tweet about what I’m seeing @SoutheastMIVeg.

General notes and meetings announcement

Curious about using drones in agriculture? Attend the Tri-State UAV Field Day Aug. 27 in Ohio. Contact Ricardo Costa at or 573-639-8971 for more information and registration.

The Midwest Mechanical Weed Control Field Day is Sept. 26 at the PrairiErth Farm (2073 2000 Ave, Atlanta, IL 61723). See in-row cultivation tools demonstrated on vegetable crops, a trade show and grower experiences with mechanical cultivation. The field day begins at 9:30 a.m. and wraps up around 4 p.m. The event registration is $20, lunch included. Check out the Mechanical Vegetable Cultivation Facebook page for more information.

It is never too early to make accommodations to attend Great Lakes Fruit and Vegetable EXPO, Dec. 4-6 in Grand Rapids, Michigan. Hotel blocks are open and tend to go fast. The combination of grower-focused, research-backed presentations and an exhibit hall featuring a diverse set of vendors make it a can’t-miss event.

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