Southeast Michigan vegetable update — May 23, 2018

Drier and warmer weather is on deck, keep an eye out for insect damage.

Corn flea beetle damage appears as a series of thin, erratic scratches on sweet corn seedlings. Photo by Marissa Schuh, MSU Extension.
Corn flea beetle damage appears as a series of thin, erratic scratches on sweet corn seedlings. Photo by Marissa Schuh, MSU Extension.


After a colder than average April and a wetter than average May (likely in top five wettest Mays on record in some counties), machinery has been fixed, errands have been run and planting is behind. This week will bring warm, summerlike weather that will hopefully dry out the area’s soils. Current models are predicting things being drier than normal for the next one to two weeks and for summerlike temperatures to continue for the next week and a half. Hopefully, this weather perks up the plants already in the field.

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. Soil temperature range in Fahrenheit at 2-inch soil depth, and rainfall is in inches, with parenthesis indicating change since last Wednesday. For a refresher on degree-days and how to get this information in your area, see “Accessing growing degree days with Enviro-weather” from MSU Extension.

Rainfall and GDD totals as of May 23, 2018


GDD (base 42)

GDDs (base 50)

5-Year GDD average (base 50)

Soil temperature range

Rainfall since April 1






6.78 (+0.49)






8.53 (+0.95)






8.18 (+1.29)


Cole crop planting will pick up as things dry out. The Enviroweather Cabbage Maggot Model for Deerfield suggests that the population has peaked, so egglaying will decrease in the coming weeks. We will likely see the beginning of cabbage maggot damage occurring in roots soon.

I saw flea beetle damage in cole crops this week. The damage appears as a series of erratic shot holes type damage on the lower leaves, and closer inspection (with minimal plant contact) should reveal the small, shining black beetles responsible. This damage can appear very suddenly, and small plants are the most susceptible (especially cotyledons). The treatment threshold is two to five beetles per plant; the smaller the plants are, the lower in that range you should be.

When scouting, try to avoid disturbing the plants, as flea beetles are highly mobile. For conventional production, there are many products available, including carbamates and pyrethroids. For a full product listing, see the “Midwest Vegetable Production Guide.” For organic production, in some studies (but not others) pyrethrins and kaolin clay have been effective. Row covers may exclude flea beetles (though it may just trap them with the crop). A good summary of the different control strategies can be found in “Managing Cruciferous and Solanaceous Flea Beetles in Organic Farming Systems.”

Bacterial diseases are popping up in basil as well as downy mildew.

The first report of potato leafhopper in hops has been made.

Large-scale pepper planting will begin soon. Pepper transplants out on black plastic should perk up as the weather takes a turn for the warm and dry.

Pumpkin planting will begin soon. For fields with a history of phytophthora, Apron treated seed should give a boost to beat the disease at germination. Orondis is a good product for this disease, but early season soil applications of this product are unlikely to prevent fruit rots. Save this product for closer to fruit set.

Potatoes are up to 4 inches tall, sprays have begun.

Emerged sweet corn is 4-6 inches tall with up to five leaves. Once there are six leaves, the plants should be large enough to deter cutworm feeding. I visited a field last week with a fair amount of corn flea beetle damage. These small, black, quick-moving beetles cause long, thin damage on the leaf that looks like a scratch. This damage isn’t the main concern with this pest, the issue is they transmit the bacterial disease Stewart’s wilt, which causes stunting and reduced yields as the plants grow.

As you are scouting, keep an eye out for the small, shining beetles and their feeding, and if they’re seen, the action you take will depend on the varieties you have planted, the number of beetles you see and the level of damage present.

  • For varieties susceptible to Stewart’s wilt, treat if six or more corn flea beetles per 100 plants.
  • For varieties tolerant to Stewart’s wilt, treat if there are more than two flea beetles per plant and 25 percent of the seedlings have severe damage.

There are many of products available for flea beetle control, including pyrethroids and carbamates. For a full product listing, see the “Midwest Vegetable Production Guide.”

Corn flea beetle

Corn flea beetles are quite small, though their dark color and sheen help you see them while scouting. Photo by University of Illinois at Urbana-Champaign,

Tomato planting is occurring as the weather allows.

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


Registration for the 2018 Weed Tour on June 27 is now open. This on-campus event highlight weed identification and control strategies.

Learn more about vegetable research and management June 28 during the Agriculture Innovation Day: Focus on Fruit and Vegetable Technologies. This year’s event is being hosted at the Southwest Michigan Research and Extension Center in Benton Harbor, Michigan. More event details and registration can be found at  Agriculture Innovation Day: Focus on Fruit and Vegetable Technologies.

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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