Southeast Michigan vegetable update – May 27, 2020

A hot weekend allowed for fieldwork, planting and plant growth. Insect pests are starting to be active and weeds are growing quickly.

Diamondback moth feeding
Diamondback moth feeding starts as windowpane feeding, and as caterpillars grow they leave numerous small to medium holes in the leaf. Photo by Marissa Schuh, MSU Extension.


Today, May 27, will be our last day of record-breaking heat. Thursday, May 28, will bring a high chance of widespread precipitation. Our next weather system will bring cool and dry weather to our area for the next week or so. The medium- and long-range forecasts are suggesting we will have warmer than normal temperatures in the next month.

The table below shows rainfall totals for the Michigan State University Enviroweather stations in southeast Michigan, as well as degree-days calculated using the Baskerville-Emin Method. Degree-day average for Commerce and Hudson is over five years, while Deerfield is over three years. Soil temperature range in Fahrenheit at 2-inch soil depth over the last week, and rainfall is in inches. Frozen precipitation is not included. For a refresher on degree-days and how to get this information in your area, see “Accessing growing degree days with Enviroweather” from MSU Extension.

Rainfall and degree day totals as of May 27, 2020


Degree days (base 42)

Degree days (base 50)

5-year degree day average (base 50)

Soil temperature range

Rainfall since April 1






6.89 (+0.24)






6.01 (+0.01)






6.68 (+0.26)

Crop updates

Early planted cabbage is cupping. For all cole crops, pests are becoming active. I’ve seen flea beetle damage in radishes and low levels of diamondback moth in cabbage. The treatment threshold in Michigan cabbage for diamondback moth is 30% of plants infested in the transplant to cupping stage and 20% in the cupping to early head stage. Nothing I have been in has hit that threshold yet. Thresholds are also available for broccoli and cauliflower.

Early in the season, pest pressure is generally lower, so starting with selective insecticides that control pests and preserve beneficial insects is a good idea. Bacillus thuringiensis (Bt) can be a good choice, as these products are selective to caterpillars and work well when caterpillars are small

I haven’t seen much cabbage maggot damage yet as we enter the peak flight period in the southern portions of the region. All discolored, stunted plants I’ve pulled have suffered from wirestem (not surprising with the amount of wet weather we’ve had).

Potatoes are up.

Sweet corn planting continues. Hot weather has pushed plantings along. The cool, wet weather has resulted in some stand unevenness. If you have particularly uneven stands, it may be worth digging up a few seeds to check for seedcorn maggot. Traps in central Michigan again caught high numbers of true armyworm and we have had plenty of south to north airflow in the past week, so keep your eye out for feeding on the leaf’s edges as you walk fields.

Tomatoes, both fresh market and processing, continue to be planted. Tomatoes on plastic are showing signs of transplant shock, processing tomatoes are looking purple. The cooler weather we had until recently and moist soils promote nutrient deficiencies of all kinds; purple tomato plants, especially if the discoloration is prominent in the veins, is a sign of phosphorus deficiency. As soils dry and the weather warms, this and many other odd nutrient deficiency symptoms may be grown out of.

I got a report of early blight in hoop house tomatoes this week. The heat and especially the hot, dewy nights could mean an earlier start for some plant diseases. Note that next week’s Great Lakes Vegetable Producer’s Network show on hoop house nutrition may be of interest.

Reach out

Please contact me at or 517-264-5309 with questions, concern, or to schedule a field visit. I have the ability to do field visits on a limited basis.

Great Lakes Vegetable Producer’s Network

The Great Lakes Vegetable Producer's Network is a live, weekly roundtable discussion during the growing season for commercial vegetable producers in the Great Lakes and Midwest region. It is broadcast live via Zoom at 12:30 ET/11:30 CT every Wednesday from the first week of May to the first week of September. You must register to be a part of the live audience. If you have a pressing vegetable production issue that you would like discussed, simply email it, along with your phone number, to

Next week’s show, “Hoop house nutrient management,” will feature Jud Reid of Cornell University and David Van Eeckhout of The Good Acre in Minnesota.

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