Michigan vegetable crop report - June 15, 2022
Extreme weather has adjusted schedules for earlier morning starts for more comfortable laboring, and some growers are documenting damage.
A climatological “ridge” is passing over us, which brought severe weather and high heat this week. One more day of the heat wave and record humidity, and then the “trough” that passed over Yellowstone is coming our way. Thunderstorms are likely for northern Michigan later in the week, possibly bringing high wind and hail. Heat will return next week. Degree day totals are ahead of normal in most of the state and water demands for crops are higher than normal with full sun and heat.
The forecast calls for:
- Sunny, hot and humid in most areas. Scattered showers and thunderstorms northwest during the day, spreading southeast into lower Michigan overnight into early Thursday. Severe storms possible Upper Peninsula, northern Lower Peninsula.
- Fair, dry, and cooler Thursday through Saturday.
- Fair, mostly dry, and warmer early next week, with a chance for showers and thunderstorms.
- Daytime temperatures in the 70s far north to 90s Wednesday. Excessive heat conditions likely south Wednesday. Highs falling back to the 70s – low 80s Thursday into this weekend. Lows gradually falling back from the 60s and 70s Wednesday into the 50s this weekend.
- Medium range guidance calls for warmer and drier than normal weather through much of the remainder of June.
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Hail damage response
Some farms experienced hail, wind, and water damage to crops and hoophouses this week in SW Michigan, and the weather system coming later this week may bring more to northern areas of the state. This is unfortunate and demoralizing. What can one do? Plants will not achieve their peak performance after hail damage. But, aside from calling your insurance adjuster and taking pictures, you can give plants their best chance for recovery.
Avoid splashing around in fields that are still too wet to avoid compaction and additional splashing onto plants, and refrain from trying to fix trellises until both fields and foliage can dry. Then, for crops that are susceptible to economically important bacterial diseases (tomatoes, peppers, onions, beans, for example), use a copper-based or sulfur-based bactericide to help prevent the spread of bacterial pathogens that can easily infect open wounds in the plant and are spread by driving rain and splashing. There are both conventional and organic options here.
Conventional growers might also consider mixing the bactericide with a broad-spectrum systemic fungicide like azoxystrobin (Quadris), pyraclostrobin (Cabrio), trifloxystrobin (Flint), and a protectant like mancozeb (Manzate) or chlorothalonil (Bravo).
After heavy rainfall, fields with a known history of Phytophthora would also benefit from additional fungicides specific for the management of oomycete pathogens. Mary Hausbeck maintains a list of effective fungicides for Phytophthora in three factsheets for peppers, summer squash and winter squash/pumpkins.
Herbicides and high temperatures
With the heat wave intersecting prime weed control time, it might be nice to review some patterns with herbicide application during hot weather. This Kansas State University article covers some important concepts.
In general, systemic herbicides are less effective in hot conditions, and contact herbicides are more effective both on the weed and in injuring crops. Some chemistries are more prone to volatilizing and moving off target in hot weather.
What about postemergence grass herbicides, where it is common to spray right over the crop and add a surfactant or nitrogen to improve efficacy?
Of the options most commonly available, fluazifop (Fusilade) and sethoxydim (Poast) are safest to spray right over their respective labeled broadleaf crops. Clethodim tends to be more injurious even under optimum spray conditions. Under hot and sunny conditions, no matter the gramminicide you choose, use the lower rate on the label with a nonionic surfactant instead of concentrated crop oil (COC), and do not add nitrogen. Foxtail, and barnyard grass will be easier to kill at these lower rates, but crabgrass will not respond as much.
Early season stand reducers
Seedcorn maggot and cutworm have been reducing stands in some west central crops. Seedcorn maggot risk declines once soils consistently hit 70 degrees Fahrenheit at 4-inch depth. Hopefully with hot weather coming, soils will warm and issues will be an unpleasant memory. High risk situations include planting very shortly after incorporation of cover crops or other organic matter. Cutworms are down in the soil during the day and come out at night to do their dirty work. Dig down around freshly damaged plants to see if they are present.
Conventional growers can apply a cheap pyrethroid to provide control. We do not have direct experience with organic options; Entrust and Pyganic do have activity against other caterpillar pests, but weigh the cost of these products against the potential for future damage. Experience in other crops suggests Bt is not effective.
How to tell if an application of uncertain efficacy is worth a shot? It depends on how many caterpillars are out, and how far they are from finishing development. In some cases, damage may mostly be in the past. So, check for damaged plants and caterpillars; small caterpillars will need more time to feed and develop, and so have the potential for more damage. Besides checking for worms, you could always flag out some freshly damaged plants, and come back the next day to see if more plants are damaged down the row.
Harvest was wrapped up in southwest Michigan but plugging on with high heat ahead, as of Friday, June 11. Rainfall last week was much welcome, but also brought extended wetness periods, leading to severe purple spot in some fields late last week. This unfortunately is not unexpected; last fall’s extended warmth let this disease ramp up, so there was plenty of inoculum. It is a good reminder to protect young fields that are ferned out with fungicide. Mancozeb and chlorothalonil can both provide protection, tebuconazole can protect against rust.
Keep an eye on your scouting reports and aster leafhopper texts in the coming week. MSU Extension has been sweeping, and numbers increased in one of the sampled fields over the past three weeks.
As of Monday, June 13, the early summer peak of cabbage maggot was still about two weeks off, based on weather at the Grant, Hudsonville, Fennville and Allegan Enviroweather stations. This pest is still active between peaks.
Organic growers on more than one farm have faced early season stand issues. Seedcorn maggot is the likely culprit in some cases, while other insects like cutworm may be active in others.
Cucumber beetles have been reported to be “worst ever” on a few farms.
With the hot weather, it is time to check fields for onion thrips. Movento or Senstar can be applied using a threshold of 0.6-1 thrips per leaf. Senstar is a premix of spirotetramat with another active, the other active does not help with thrips control. Movento should be applied prior to bulbing, so if you are growing transplanted onions, and want to apply Movento, keep an eye on plants. Cornell thrips control guidelines from 2021 are here.
Early tomatoes are being pruned and the first trellis strings are being installed.
Colorado potato beetle larvae are feeding along with adults laying eggs.
Strawberry harvest continues. Maintain fungicide coverage to protect the leaves and help prevent fruit rots as fruit continue to ripen, especially with the heat and afternoon rain chances this week. The heat, humidity and especially yesterday’s storms may shorten the season for some growers. Slugs have been reported in some fields.
This workshop will explain the difference between risk and uncertainty and describe risk-reducing opportunities. Then participants will gain experience reducing risk in a game-like setting where insurance is available for reducing risk. At the end of the workshop, participants will better understand opportunities for reducing risk and acquire some experience reducing risk in a game-like setting.
Date: June 16, 2022
Time: 6:00 pm to 8:00 pm.
Place: Lake Michigan College – South Haven Campus
Virtual Workshop will be at the same time via Zoom.
This work is supported by the Crop Protection and Pest Management Program [grant no 2021-70006-35450] from the USDA National Institute of Food and Agriculture.