East Michigan vegetable update – May 15, 2019

Growers are catching up this week.

Plasticulture sweet corn
A glimpse at plasticulture sweet corn. The corn on bare ground was seeded, covered and sprayed with a preemergent herbicide in one pass in mid-April. The corn on black plastic was seeded in mid-April in 92- and 128-cell trays in a hoophouse and transplanted/covered two weeks ago. Both are varieties with expected maturity of less than 70 days. The growers are targeting the first week of July for harvest. Photo by Ben Phillips, MSU Extension.


We are likely clear of frost in Michigan’s southern Lower Peninsula.

Traps in southeast Michigan caught a flight of black cutworm moths on May 8 with the weather system that came up from the southwest. Wet soils and weedy fields are a perfect place for black cutworm moths to lay eggs and thrive. Timely herbicide application, or tillage to bury weed residue, is typically the key to avoiding a black cutworm infestation.

Here is a table that summarizes the maggots of concern and the degree days that signify when they will be laying eggs in the areas around seedlings. I used Lapeer as an example. The seed corn maggot and cabbage maggot models are from Michigan State University’s Enviroweather, and the onion maggot model is from NEWA. Both onion maggots and cabbage maggots began to emerge in the last week, but peak flight has yet to occur. Delay planting if possible, or time banded insecticide applications for the peak flight of overwintering flies.


Seed corn maggot emergence - base 39 F

Onion maggot emergence – base 40 F

Cabbage maggot emergence - base 43 F

Current degree days (Lapeer)




Overwintering flies start to emerge and lay eggs

201 (occurred 18 April)

390 (occurred 15 May)

298 (occurred 11 May)

Peak flight and egg laying of overwintering flies

342 (occurred on 4 May)



Peak flight and egg laying of first generation flies




Peak flight and egg laying of second generation flies




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

Vegetable crops

Regarding greenhouse management, I visited a grower utilizing tall wooden raised beds in a greenhouse, approximately 3 feet tall. They were left over from a previous owner, with nice irrigation plumbing that made it seem wasteful to tear them out. Their goal was to maintain a 12-month supply of tomatoes by replacing old plants with new plants within the same beds. Basically, a mixed-age planting within each bed. Major pest issues were choking out the older plants and adding new plants right into that biohazard would not work out.

Remember, greenhouses are built for sanitation. That is their advantage, and you should work with that natural advantage. Separate plantings between houses or bays. Keep transplants in a separate area. Travel through the cleanest areas and transplant areas first. If you work with built raised beds, they should be treated like tiny fields that need breaks, remediation and rotation.

Field preparation is on-going as conditions allow.

Asparagus picking has begun in fits and starts. The purple varieties are farther along. Asparagus beetle feeding damage is showing up on young spears with heavy straw mulch around them.

Garlic is showing some nitrogen deficiency (yellowing midrib and leaf tips), likely from cool soils. If you have not removed the straw mulch yet, this could be part of the problem. However, garlic does tend to do this regardless.

Some sweet onion transplants are still going in, and that is a bit late to get large bulbs. Long-day varieties are triggered to bulb as days get longer. Once they are triggered, they do not grow as much leaf mass. The goal is to achieve as much leaf mass as possible before they are signaled to bulb by the lengthening days leading to the summer solstice in late June.

Heated hoophouse tomatoes are charismatically showing how they feel. Magnesium (Mg) deficiencies are showing up as mottled yellowing between the veins of the oldest leaves. This is very common around fruit set time. In some houses with high soil pH, manganese (Mn) deficiencies are also showing up as mottled yellowing between the veins of the newest leaves. It is unfortunate those two nutrients sound so similar, with similar symptoms: one (Mg) occurring more on the oldest leaves, and the other (Mn) on the newest leaves. If left unaddressed, both can eventually occur on all leaves of the plant. Just make sure you are addressing the right one!

Recent soil tests can help parse through the diagnosis, and it is also worth while to send leaf tissue samples to a good lab to see what is happening in the plant. JR Peters (phone: 866-522-5752) in Allentown, Pennsylvania, and A&L Labs (phone: 260-483-4759) in Fort Wayne, Indiana, are great labs for this type of service. Both can send you test kits with instructions and sample forms to mail back, but A&L is about half the price. It might help to call them for any specifics that would help you get them a good sample. Be sure to wash the leaves before sending so that any foliar applied nutrient or pesticide residues do not skew your results.

I walked a hoophouse with dead weeds in it this week and bleaching in the newest tomato leaves. Gluttonous use of glyphosate can gum up the growth of great tomatoes.

Heated hoophouse cucumbers were on their sixth flower node at a hoophouse in the Thumb this week. They were a seedless variety called Excelsior.

Early sweet corn plastic has not been removed.

Zucchini, summer squash and cucumbers were being transplanted into the field on black plastic and under low-tunnels this week.

Tomatoes and peppers were both being transplanted into the field on black plastic and under low-tunnels last week, and in one case the peppers froze out. We are thinking it was because the plants were set and tunnels were finished up in early evening, without much sunlight left to bank up some heat in the tunnels. However, if temperatures were low enough, then even a morning planting would not have helped.

A question came to me this week about mixing sweet and hot peppers. Will the hot pepper cross-pollinate with the sweets and turn them hot? The answer is no. Just as a pregnant woman does not take on the appearance of the man who impregnated her. However, the seed might grow into a plant that might produce more capsaicin. Just as how a baby might grow up to have mother’s eyes and father’s hair color. Unless you are saving seed, cross-pollination is nothing to worry about with peppers.

Potatoes have been planted under plastic for early “new potato” harvest in some areas, and bare-soil plantings are still taking place. The earliest plantings are poking leaves out, and Colorado potato beetle will be soon to follow.

Rhubarb picking is underway, with shoots about 14 inches long, and still a lot of green color. Seed stalks are already forming on some varieties and growers have been snapping them off at picking to concentrate the plant’s energy on the roots and stems.


We are planning one more Produce Safety Alliance (PSA) Grower Training event in South Haven, Michigan, on June 4. If you were hoping to sign up for an On-Farm Readiness Review this season, we ask that growers attend a PSA Grower Training before scheduling an On-Farm Readiness Review! This will be the last opportunity to participate in a grower training, and therefore an On-Farm Readiness Review, until this coming October! Register here: Produce Safety Alliance (PSA) Grower Training.

It is never too early to make accommodations to attend the Great Lakes Fruit, Vegetable and Greenhouse Growers EXPO, Dec. 10-12 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.

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 Diagnostic Services.

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