MSU Extension

This week’s regional reports:

• Southwest Michigan – Ron Goldy
• Central Michigan – Fred Springborn
• Southeast Michigan – Lina Rodriguez Salamanca

Southwest Michigan – Ron Goldy, Michigan State University Extension

Weather

Temperatures for the period were again above average with highs from 80 to 90 degrees Fahrenheit and lows from 54 to 66F. The area received an inch or more of rain. There was also damaging hail reported from the thunderstorms that moved through early morning Tuesday, July 31. More frequent rains have kept the top several inches of soil moist, but deeper levels are still dry.

 Crop Reports

New weed growth is quite noticeable after recent rains. Main weeds in many fields are crabgrass and carpet weed.

Growers of fall squash and pumpkins are finding a large number of male flowers in their plants. This is due to the hot weather over the past month and as long as the plants are healthy, they should be making female flowers over the next couple weeks. So don’t give up, it only takes 30 to 40 days from pollination to maturity so there is still plenty of time to make a crop.

Unfortunately virus symptoms are increasing in many vine crop fields. Care needs to be taken in yellow squash and zucchini fields since the virus can be transmitted on cutting knives. At the minimum, knives should be sterilized between fields, or at the end of rows. Ideally it would be after every plant, but that would be unrealistic. Once plants have virus they will always have it, but the fruit set prior to infection should be okay.

Downy mildew has been confirmed in the area and the wet, windy, and cloudy conditions are ideal for spore movement. So cucurbit growers, especially cucumbers, need to make sure their crops are adequately protected.

Mites continue to be a problem in vine and Solonaceous crops. Aphid populations are also increasing in peppers.

Potatoes are senescing early but regrowth is occurring at the base of the shoots. Some potatoes planted early May still have not set tubers due to the heat. Leafhoppers are present.

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Central Michigan – Fred Springborn, Michigan State University Extension

Weather

I feel maybe too much like bragging when I report 1.25 inches of rain fell at the MSU Experiment Station at Entrican this week giving irrigation systems a break. Other parts of the central region have reported as much as 3 inches for the week. The driest soils remain on the south edge of the region where subsoil moisture remains low.  High air temperatures were in the mid 80s with lows in the upper 50s to low 60s.

Crops

Potato vines in several fields continue to deteriorate, many are declining sooner than what is optimal. Colorado potato beetle is present in all life stages. While there have not yet been any reports of late blight in Michigan it is important that growers maintain preventative fungicide applications.

Summer squash and zucchini harvest is continuing with fruit growing rapidly. Powdery mildew is present in many fields.

Pickle harvest is underway with fruit developing rapidly. I have NOT found downey mildew as of yet in Montcalm or adjacent counties, though I have had a few calls which turned out to be other leaf disorders.

Western bean cutworm pheromone trap catches continue to taper off. I am down to catching 1 to 2 per night likely indicating the end of flight is near. Scout sweet corn for western bean cutworm egg mass if at or near tassel emergence for the next week, especially if the planting is not receiving insecticide treatments for European corn borer or corn earworm.

We continue to catch low numbers of corn earworm.

Potato leafhopper adults and nymphs are present but lower numbers are being observed this week than in previous weeks.

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Southeast Michigan – Lina Rodriguez Salamanca, Michigan State University Extension

Weather

In the past week, relative humidity on the Hudson Enviro-weather station ranged from 30 to 93 percent with 5 to 15 hours of wetness. At the Petersburg Enviro-weather station relative humidity ranged from 31 to 94 percent with 3 to 17 hours of wetness.

Crops and pests

Watermelon, muskmelon and other cucurbits harvest continues. Squash and zucchini harvests are coming to an end. No more squash vine borer has been caught in Monroe County, and only one moth was found in the Washtenaw County traps. No more eggs will be laid (based on degree days).

In the Monroe spore trap, cucurbit downy mildew (CDM) counts reaching 10 spores per hour last week. Three counties – Tuscola, Berrien and Arenac – in Michigan have confirmed CDM reports (see map with counties and dates).

Cabbage and leafy greens harvest continues. Some growers struggle to control thrips on cabbage due to the hot and dry weather.

Potatoes and peppers harvest has started. Tomato hornworms are active in some fields in Washtenaw County. The risk for late blight continues to be moderate in our area.

Eggplants are bearing fruits and in some fields, mites are present and abundant.

Sweet corn harvest continues. The risk of western bean cutworm is changing from high to moderate in our area. The InsectForecast website is indicating the beginning of the end of the western bean cutworm migration. The risk for corn rootworm is high. The count of insect pests in the Monroe County traps was:

• 1 CEW - Corn earworm
• 0 ECB - European corn borer
• 1 WBCW - Western bean cutworm.

Monitoring will continue.

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