Southeast Michigan vegetable update – May 31, 2017

Waiting for things to dry out on your operation? You aren’t alone! Catch up on the status of diamondback moth, true armyworm, and seedcorn maggot in southeast Michigan.


This weekend saw storms that brought lots of rain in relatively short periods of time and some hail damage has been reported. This week will likely be cooler than normal for this time of year and there is likely to be some windy mornings and sprinkles moving through the area. There is a chance of rain this weekend.

The table below presents inches of rainfall for the Michigan State University Enviroweather stations in southeast Michigan with the amount of change from last week reported. Degree-days (starting March 1) are calculated using the Baskerville-Emin Method. The soil temperature range (top 2 inches) during the last seven days is also included when available.

Rainfall and degree-day totals as of May 31

Enviroweather station

Degree-days (base 50)

5-year degree-day average (Base 50)

Rainfall since April 1 (inches)

Soil temperature range


384 (+75)


6.51 (+0.5)



508 (+93)

Not available

7.64 (+1.36)



414 (+82)


7.15 (+1.23)



Asparagus harvest has wrapped up on many operations.

Cole crop pests are beginning to appear. Diamondback moth larvae are present in some cabbage plantings and sprays have begun. I’ve seen cabbage white butterflies (the adult form of the imported cabbage worm) flying and laying eggs, so caterpillars are currently or will soon be out. Review pest identification and thresholds before pest activity is fully underway with MSU Department of Entomology professor Zsofia Szendrei’s “Caterpillar Pests in Cole Crops.”

The first harvest of kale planted as transplants on black plastic will begin soon.

dimondback moth pupae

The presence of a diamondback moth pupae on this cabbage suggests that this pest has been present for approximately two weeks. Photo by Marissa Schuh, MSU Extension.

Watermelon and muskmelon transplants are going in on black plastic.

Pepper planting continues as weather allows.

Potatoes were going in last week.

Pumpkin planting began last week. For those planting pumpkin and winter squash, note that seedcorn maggot flies are currently out and laying eggs, with the peak of egg laying predicted for June 1 in Deerfield, Michigan. The fields most attractive to this pest have recently killed or incorporated vegetation, be it cover crops or weeds.

Fields where the 4-inch soil temperature has held above 70 degrees Fahrenheit for more than five consecutive days have been shown to be less attractive to flies. At the Deerfield Enviroweather station, the 4-inch soil temperature has reached at least 70 F since May 26, but soil temperature is highly variable by location.

If you can’t avoid planting vine crops in the next couple of days, try to use seed treated with thiomethoxam. For more prevention options, see the Midwest Vegetable Production Guide for Commercial Growers. Call me at 517-264-5309 or visit the Lenawee County MSU Extension office to purchase a copy.

Sweet corn plantings are coming along nicely. Be aware true armyworms and black cutworms are out in southeast Michigan. True armyworm feeds on the edges of leaves, which gives them a ragged appearance. They feed when it is darker out and hide in debris or the whorl during the daytime — the worms themselves have distinct horizontal stripes running down their body.

The threshold for this pest is more than 35 percent of plants are infested during the seedling or early whorl stages. If your scouting reveals armyworms in 10-35 percent of plants, scout the field again in three days. For information on scouting, risk and damage thresholds, see MSU Extension’s “Pheromone catches of early-season pests cue sweet corn growers to do early-season scouting.”

two views of armyworm

Two views of true armyworm. The caterpillars are most likely to be seen feeding on the leaves when it is dark out, and will hide themselves during the day. Photo by Marissa Schuh, MSU Extension.

Processing tomato planting continues when a dry field can be found. In the earliest plantings, some frost damage from earlier this month is being fully realized and some replanting is occurring. Wind damage from last week’s high winds has been seen and the wet weather has many fields quite wet—fungicide sprays will likely begin when weather/field conditions allow. There has been some damage from drift in some plantings. The earliest plantings have a few flowers coming in.

Staked tomatoes look good and stakes have been placed.

Some greenhouse tomatoes are red and being harvested. There have been some problems with aphids, which leave honeydew that often develops a black mold. This residue is impossible to remove so catching aphid populations early and treating before they can leave high amounts of residue is the best course of action. For insecticides labeled for aphids and other greenhouse pests, see MSU Extension’s “Insecticides for common pests on greenhouse vegetables and transplants.”

Contact me at any time for pest/disease sampling at 517-264-5309 or I make updates regularly on Twitter at @SoutheastMIVeg.


Organic growers and others who use compost: If using compost from a municipal source, be sure to do some kind of test for weed seeds. This can be as simple as potting some of the soil and letting any weed seeds present sprout (though doing a test in spring won’t catch any weeds that emerge in the fall). Failure to screen yourself or get records from the composter that compost has been treated in a way that weed seed death is likely can lead to the introduction to new weeds (and perennial problems) into your fields.

It is never too early to make accommodations to attend Great Lakes Fruit and Vegetable EXPO, Dec. 5-7, 2017, in Grand Rapids, Michigan. The combination of grower-focused, research-backed presentations and an amazing exhibit hall make it a can’t-miss event.

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