Southeast Michigan vegetable update – June 14, 2017

Hot days and nights dry out topsoil and boosts degree day counts.

Asparagus beetle larvae look similar to caterpillars, just with only three legs. They may emit green liquid when disturbed. Photo by Clemson University - USDA Cooperative Extension Slide Series,
Asparagus beetle larvae look similar to caterpillars, just with only three legs. They may emit green liquid when disturbed. Photo by Clemson University - USDA Cooperative Extension Slide Series,


Hot, summer-like weather has rapidly dried topsoils, and irrigation pumps are running across southeast Michigan. Soils are very hot, so be careful if planting without irrigation. There is a chance of rain both on both June 14 and June 15, though the greatest chance of rain is this weekend as a cold front moves in, bringing in below-average temperatures for next week.

The table below presents rainfall (in inches) for the Michigan State University Enviroweather stations in southeast Michigan with the amount of change from last week reported. Degree days (starting March 1) calculated using the Baskerville-Emin Method.

Rainfall and degree-day totals as of June 14


Degree-days (base 50)

5-year degree-day average (Base 50)

Rainfall since April 1 (inches)


628 (+155)


6.62 (+0.04)


789 (+170)

Not available

7.95 (+0.27)


685 (+164)


7.27 (+0.1)


Asparagus harvest has wrapped up and plants have developed ferns. Some plantings have a good number of asparagus beetle larvae. This pest can damage spears, but at this point in the season larval feeding on the ferns are of concern, because this feeding can weaken the plant which may make it more susceptible to disease and reduce the productivity of the stand next year. Treatment is recommended if there is 10 percent defoliation or 50 percent of the plants have larvae on them. Organophosphates or carbayl are effective in treatment and Entrust is an available organic option.

Cole crops are growing steadily. The earliest planted cabbage is cupping. Some young stands have uneven stand development, likely due to patchy field moisture and soil compaction. Seedlings that have gone out in the last week are stressed from the hot weather.

Peas are being harvested on some farms, depending on the variety.

Pepper planting will wrap up soon.

Potato planting has wrapped. The farthest along potatoes I’ve seen are flowering. Be alert as potato diseases are emerging, with potato Y virus, aerial stem rot, blackleg and tuber soft disease popping up in Michigan potato fields. Potato virus Y is transmitted by aphids, and the appearance of the disease will vary by cultivar. I saw the virus in a purple skin specialty potato variety manifesting itself as warped and necrotic lower leaves.

The other three diseases are caused by bacteria and cause mushy potatoes and stems. Aerial stem rot infection occurs when the pathogen enters the plant through a wound or natural opening on the stem, the area around this infection point will become brown, slimy, and mushy.

Blackleg produces similar disease symptoms, but the disease comes in with the seed (either from the supplier or sometime during the handling/transportation process), so the seed piece will be black, liquid and smelly.

Tuber soft rot infection produces potatoes with small, cream/tan, water-soaked lesions on potatoes and infected areas will turn brown when exposed to air. If you see potatoes wilting in your field, it is worth taking a closer look. I am available to take plants with suspected disease up to campus.

For more information, see the MSU Extension article “Aerial stem rot, blackleg and tuber soft disease reported in Michigan potato fields” and bulletin “Tuber Soft Rot, Blackleg and Aerial Stem Rot”.

Pumpkin planting is wrapping up and germination has begun. Some plants have up to four to five leaves. Squash vine borer adults are beginning to emerge according to Enviroweather models. I haven’t detected any moths yet in my traps in Lenawee and Monroe counties.

For strawberry growers finding small, bronzed berries in their rows, see the MSU Extension fruit team’s run through of the causes in “Why are the strawberries so small this year?.”

Some light summer squash harvesting is underway.

Sweet corn is nearly waist height. The warm weather likely has corn rootworm hatching. As silking nears, note that pyrethroids have reduced effectiveness against corn earworm. Some research has shown that pyrethroids may still be effective when corn earworm pressure is low. Radiant and Coragen are the other available options for treating this pest.

The end of processing tomato planting is in sight. More flowers continue to develop on early plantings.

Market tomato field work continues, with stakes being placed and manual weeding being done.

As we approach the time that muskmelon and watermelon bloom time, note that sprays should be done late in the day in order to not harm pollinators. If you are trying to gauge the level of bee activity in your field, look for bees mid-morning as opposed to later in the day.

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


If you’re interested in participating in a statewide survey of squash bees, there will be a webinar June 15 from 3-4:30 p.m. focused on squash bee identification and how to report sightings to MSU researchers. For information and registration, visit “Squash Bee Pollinators and EMG Citizen Science Project.”

Those interested in the burgeoning local oat market can attend the “Oat Twilight Crop Walk” from 6-8:30 p.m. at Zilke Vegetable Farm in Milan, Michigan. For more information and registration, see “Local oats for fresh milling featured at Washtenaw County Field Day.”

The 2017 MSU Weed Tour will be June 28 at the MSU Agronomy Farm. For more information and registration, see “2017 MSU Weed Tour scheduled for June 28.”

Hotels are filling up for the Great Lakes Fruit and Vegetable EXPO, Dec. 5-7 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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