East Michigan vegetable update – Aug. 19, 2020

Harvests are well underway in all crops, and some older fields and rows are being shut down.

Grafted tomatoes
Grafted tomatoes that got too big for their britches. Photo by Ben Phillips, MSU Extension.


Short term forecast is for sunny, warm and dry through Saturday, Aug. 22, with scattered showers possible on Sunday. Temperatures will warm to near to above normal levels into the weekend, with highs in the 80s and lows warming from the 50s into the 60s. Medium range forecast suggests a cool and unsettled weather pattern for late August/early September.

You can find more detailed weather information for your area by visiting the Michigan State University Enviroweather station closest to you:

Here is a table that summarizes European corn borer activity, based on growing degree day (GDD) models. I used Lapeer as an example.


European corn borer emergence – Base 50 F

Current degree days (Lapeer)


Overwintering generation start to emerge and lay eggs

450 (occurred June 11)

Peak flight and egg laying of overwintering generation

700 (occurred June 28)

Peak flight and egg laying of first generation

1,700 (occurred July 31)

Peak flight and egg laying of second generation


Phytophthora Phthought

This disease is kind of like diabetes of the farm. If diagnosed, you will be living with it and will need to change certain practices and behaviors to reduce its effects on the long-term productivity of your business. It can be overwhelming to read about this plant destoyer. So, here is just one thought at a time for anyone going through this.

When trying to make the best of a field showing symptoms in the late season, you can harvest fruit that are not soft before they are fully ripe. Peppers, tomatoes, hard squash and pumpkins can be stored for a while and monitored as they ripen. Save these sections for harvesting last, and do not cross over uninfested fields afterwards until equipment is washed.

Tune in to the Great Lakes Vegetable Producer’s Network next week to partake in a conversation with leading Phytophthora expert, Chris Smart, from Cornell University. We broadcast live via Zoom at 12:30 ET every Wednesday from the first week of May to the first week of September. Listen live or later.

Crop progress and pests

Brassica root crops are being planted again for fall harvest, like turnips and rutabaga. Also, red beets and radishes are still going in. Flea beetle pressure seems to have been constant through the whole season. We think this may have been from the mild winter.

Sweet corn harvest is shutting down on some farms. Others will be trucking on into late September. Corn earworm moth catch is still very low and below treatment threshold, with one to 1.5 moths caught per night.

Cucumber harvest continues. Some samples were sent to the lab with squash mosaic virus (SqMV). This virus is transferred by cucumber beetles. Another sample came in with tobacco ringspot virus (TRSV). This virus is quite rare in the north, but is sometimes seedborn and transferred mainly by nematodes, but also mites and thrips.

Pumpkins and most winter squashes are being harvested on some farms for direct sale or display right now, and for protected ripening under trees, and in sheds and barns. Some farms are seeing plants dying down from defoliation and wilting. The causes seem varied, from Septoria leaf spot, Fusarium wilt, Phytophthora wilt, paraquat drift, vine borer, potential nutrient deficiencies, and plain old tired plants with a heavy fruit load.

Summer squash and zucchini are still going strong on some farms but are experiencing more disease pressure and looking sad.

Field tomatoes, peppers and eggplants are being picked. Strong rain and wind can knock off flowers and fruit and can open up the canopy on these crops, exposing the fruit and causing sunscalds. One grower I visited experienced a trellis tip-over with Red Deuce grafted on Maxifort. After years of decreasing plant vigor in an unrotated tomato hoop house, the grafted stock put on growth that they had not seen in a while. And so, their trellis was incapable of handling it.


Now is a good time to send in weed seed if you think it is resistant to herbicides. Don’t bother sending marestail. We know it’s basically resistant to the main herbicides across the whole state. The Michigan Vegetable Council is funding resistant screening for anything else. You can use this form and ship before mid-November.

$$$$ MONEY $$$$

You know me because I am your vegetable doctor, and you have come to know what I can help you with. I have colleagues that are like business doctors, offering similar consultation services as I do with plant health, but with financial health. Due to faculty turn-over from retirements, they are all brand new employees learning the ropes! They really want to know what they can do to make your business maintain or increase profitability. Help them help you by answering these three questions.

Also, just so you know, there is money available for COVID-19 relief for growers with fewer than 10 employees, and also for growers with more than 10 growers.

Please contact me at phill406@msu.edu or 616-901-7513 with questions, concerns, or to schedule a farm visit. You can also send plant materials to MSU Plant & Pest Diagnostics.

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