East Michigan vegetable update – July 19, 2017

Harvest of warm-season vegetable crops continues. Cool-season, single-harvest crops like cole crops are being harvested and replanted for fall. Machine pickle harvest has begun.


We have warm and wet days ahead of us this week. Nights are predicted to get down to 60 degrees and may reach dew points in many areas, which increases the amount of water that stays on leaves.

The table below shows growing degree-days (GDD) base 50 degrees Fahrenheit since March 1, rainfall (inches since April 1) accumulations and soil temperature ranges (Fahrenheit over the last week) to date from Michigan State University Enviro-weather stations in the region.

Rainfall and GDD totals as of July 19, 2017


GDD (+ added from July 5)

GDD 5-year average

Rainfall (+ added from July 5)

Rainfall 5-year average


1,282 (+ 302)


11.79 (+ 1.83)



1,294 (+ 291)


9.34 (+ 0.00)



1,443 (+ 315)


14.78 (+ 2.77)



1,351 (+ 299)


12.96 (+ 0.37)



1,317 (+ 296)


18.04 (+ 7.72)



1,318 (+ 293)


11.07 (+ 2.73)



1,230 (+ 291)


20.03 (+ 0.46)



1,326 (+ 298)


12.86 (+ 0.62)



1,379 (+ 314)


12.31 (+ 3.66)



1,213 (+ 292)


11.57 (+ 0.96)



Corn earworm catches remain low in sweet corn, under five moths per night. A five- to seven-day spray schedule is adequate for now. Western bean cutworms are being caught. Do you think you are seeing corn earworm resistance to pyrethroids? Test your coverage with water-sensitive cards before jumping to conclusions. Sprays should be reaching the silks.

In pickles, downy mildew has been found in Bay County. Machine harvests started last week. MSU Extension plant pathologist Mary Hausbeck’s downy mildew recommendations for 2017 suggests at least a three-product rotation of Gavel 75DF, Orondis Opti SC, Ranman 4SC, Zampro 4.4SC and Zing! SC. Each material needs to be tank-mixed with Bravo Weatherstik or Mancozeb.

Cantaloupes are being harvested, but watermelons are still sizing. See pickle section for fungicide recommendations for downy mildew. Alternate those products with powdery mildew products like Quintec, Torino, Vivando or Rally. Some bacterial issues were evident on some farm visits last week, and treflan injury was evident in one field where the boom charged at the end of the rows.

Summer squash pickings continue. Winter squash and pumpkins are flowering and setting fruit on some farms. Squash bees are active. Some growers have just begun treating for powdery mildew. See cantaloupe section above for powdery mildew products.

Hausbeck has been receiving more vine crop samples infected with phytophthora. This is an important disease for the long-season winter squashes and pumpkins. She secured a Michigan 24(c) label for Orondis that allows for two consecutive sprays of this product if the phytophthora spray program only consists of two sprays. If the phytophthora spray program consists of three sprays, then Orondis can only be used once. The label language and packaging have been tricky since the release of this new product.

Fresh market field tomato picks are continuing. More farms are picking now. Late blight was confirmed in potatoes in St. Joseph, Michigan. Apply Bravo or Mancozeb as protectants against this disease when we have a string of dewy mornings and cloudy days. A lot of growers like using Mancozeb (five-day pre-harvest interval) while tomatoes are still green, and switch to Bravo (one-day pre-harvest interval) once picking begins.

Bell peppers are sizing up and walls are thickening. The flavor isn’t there yet in some plantings. They still taste bitter and vegetative. Be careful which peppers you taste-test! Hot Hungarian wax peppers look just like sweet banana peppers.

The few eggplants I see on my rounds are large and flowering, but still no fruit. Colorado potato beetle pressure appears to be low this year for many growers.

Thrips populations in onions are increasing. MSU Extension entomologist Zsofia Szendrei recommends growers should be on their second spray of Radiant at the lower rate. A penetrating or non-ionic surfactant is a must at a rate of a half-gallon surfactant per 100 gallon tank-mix. Trade names for some of these include Silwet, MSO and Dynamic.

Cole crop plantings continue for fall harvest. Spring plantings for broccoli, cauliflower and cabbage are being harvested. I’ve gotten reports of diamondback moth that is not controlled by pyrethroids. They are known to be resistant to many pyrethroids (Group 3A) and many carbamates (Group 1B).

Growers experiencing poor control after many years of 1B and 3A insecticides need to being using new modes of action:

  • Intrepid: Group 18, one-day pre-harvest interval
  • Coragen: Group 28, three-day pre-harvest interval
  • Proclaim: Group 6, seven-day pre-harvest interval for head/stem brassicas, 14-day pre-harvest interval for leafy brassicas
  • Radiant: Group 5, 1-day pre-harvest interval

Bt products, such as Javelin or Zentari (Group 11, zero-day pre-harvest interval), do a great job controlling cabbage whites and diamondback moth before cabbage looper arrives. Bt is specific on caterpillars, as well as conserves parasitoid wasps.

When moth pressure increases and cabbage looper migrates up, begin using Intrepid, Proclaim and Radiant, which are more aggressive on higher moth populations, but have a lower impact on parasitoids than Group 1B or 3A insecticides. Coragen can also be effective at killing caterpillars and conserving parasitoids as a chemigation treatment through drip.

Upcoming meetings

The Midwest Mechanical Weed Control Field Day is Sept. 26 at the MSU Horticulture Farm. For more information and registration, see “Midwest Mechanical Weed Control Field Day.

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.

Please contact me at phill406@msu.edu or 616-901-7513 to pick up any suspected disease samples from your farm, or send the diseased plant parts to MSU Diagnostic Services.

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