East Michigan vegetable update – July 10, 2019

Harvests are ramping up, but not in the order that is expected.

This side-by-side comparison of three-week old lettuce roots (top) and seedling onion roots (bottom) show growth in tilthy soils (left) and compacted soils (right). A high water table can create a shallower root system similar to the images on the right by preventing respiration of root tissues. Source: Weaver and Bruner, 1927 “The Root Development of Vegetable Crops."


There is a cold front predicted for tonight, July 10, bringing approximately 0.25 inches of rain. With the fruit loads on vine crops and tomatoes right now, this will be a welcomed shot. The next week will be warmer than normal, with highs in the mid-to-high 80s and low 90s. Expect to see wilting from these conditions and from cultivation between the rows.

Weaver and Bruner published an amazing book in 1927, “The Root Development of Vegetable Crops,” with line drawings in 1-foot by 1-foot grids. These drawings clearly show how far some of our vegetable crops really reach. This year, deeper roots stopped at the high water table, and so plants are now relying on those shallower side-ways growing roots, which will be prone to drying out and cultivator blight. I am already seeing “flash drought” symptoms in field corn with the classic pineapple-like leaves in fields with obvious flood damage, and a pumpkin grower in the region reported wilting from root damage after cultivating. Strange year.

Since so many field crops got in late this year, the season for spraying herbicides has also been extended. Keep an eye out for herbicide drift this season throughout the month of July. If you want resolution from the Michigan Department of Agriculture and Rural Development (MDARD), you must report it within 30 days for any sampling to be effective at confirming the chemistry that caused symptoms.

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 models. I used Lapeer as an example. I removed the seed and root maggot data because those pests are not much of a threat going forward.

European corn borer emergence – Base 50 F

Current degree days (Lapeer)

940 GDD

Overwintering generation start to emerge and lay eggs

450 GDD (occurred June 11)

Peak flight and egg laying of overwintering generation

700 GDD (occurred June 28)

Peak flight and egg laying of first generation

1,700 GDD

Peak flight and egg laying of second generation

2,450 GDD


In cole crops, the canopies of early plantings are now coming together and final hoeing passes were taking place this week. I saw cabbage heads in Bay County about 4 inches in diameter. Broccoli heads are small. Swede midge continues to be a presence in Sanilac County. Diamondback moth pressure is under threshold at most farms (40% of broccoli/cauliflower plants or less with larvae on them), and the season for flea beetles appears to be extended like strawberry harvest. Other caterpillars have not been very prominent yet.

Transplanted sweet onions are being harvested. Some leaf blights are beginning to show up in these fields as tip dieback. Stemphylium and Alternaria are two fungal pathogens that form dark circular sporulation spots on these dying leaf tips. Stemphylium forms smaller rings of spores than Alternaria, and his harder to control. MSU’s Mary Hausbeck conducted fungicide trials and found that the best products for Stemphylium are Luna Sensation, Luna Experience or Luna Tranquility, Bravo, Omega, Tilt, Tebuzol and Approvia Top.

Further, with the dry and hot weather in the near forecast, thrips could be on the rise over the next week.

Garlic is being harvested. This is uncured for immediate consumption, similar to sweet onions.

Sweet corn plantings are pollinating. Corn borer caterpillars are showing up in the whorls right on schedule. The development of this insect is temperature dependent and predictable. Peak flight and egg-laying of the adults occurred June 28, and now the caterpillars have hatched and begun causing the birdshot holes in the leaves in the whorl. Insecticides should be applied before the caterpillars bore into the tassel stalk. A boom that directs sprays down into the whorls works best.

Pickling cucumber plantings are far from complete. Growers are planting daily to catch up with a goal of finishing by the end of this month. Harvest has not yet begun. Cucurbit downy mildew spores have been caught in spore traps in Allegan County this week, but field symptoms have not yet been found. Start protectant fungicides now.

Zucchini and fresh market cucumbers are being harvested and also planted. I received a report of fruit abortions in hoophouse cucumbers last week. The temperatures were over 90 F in the hoophouse, even with full ventilation and fans running. When the temperatures get over consistently over 80 F, cucumber plants that have set fruit already will suppress the formation of more fruit. Tomatoes, peppers and eggplants will also suppress fruit set at around 90 F. That is just a tough shake in the summer time. Two options to consider if vents and fans are not enough are shade cloth, or creating an evaporative cooling effect by wetting the soils between the rows, installing irrigation misters, or constructing a DIY cooling wall.

Watermelons and melons are in various stages, with the earliest plantings beginning to fill the row middles and with fruits about 6 inches in circumference. Start protectant fungicides now for downy mildew and powdery mildew. Cucumber beetles are out, but I have not seen them in high numbers.

Pumpkins are still being transplanted. This week is the absolute last opportunity to make yield from transplanted pumpkins. Seeded crops will not make yield at this point. For fields with a history of phytophthora, this year could be rough. Products for root rots should be applied to the soil at the base of the plant through drip irrigation or directed high volume spray. Drip application works much better than a directed spray. Foliar applications should be used for fruit protection. It is difficult to achieve good coverage as foliage gets larger. Quadris is not effective anymore. Orondis Ultra, Ridomil, Elumin, Presidio and Revus are better products for this.

Peppers are small and fruiting. They will not do well this year. Fifty to 60 pounds of nitrogen can help kick them in to more vegetative growth, but most plantings that I have seen are already devoting a lot of energy to flowers and fruits. Phytophthora root rots could be a problem for peppers this year as well. Similar to pumpkins and squash, Quadris is not effective anymore for this disease. The best control is offered by products delivered through drip irrigation, and soil or stem-directed sprays do not work well.

Hoophouse tomatoes are being harvested in volume now. Some gray wall symptoms are showing up in some plantings. This is a complicated nutrient issue that is not easy to diagnose or solve. Suffice to say, a lack of potassium is often the cause. Either from not enough of it, or from competition from other more available nutrients.

I received my first report of field tomatoes going to market in Linden. Early blight is showing up in both field and hoophouse plantings.

Red beets and radishes are being harvested and planted.

Asparagus picking is wrapped up, and summer weed control between final harvest and fern growth is the next step.

Strawberry picking continues, and it will soon be time to renovate strawberries.

Get togethers

The Young Growers Exchange Bus Tour is designed to allow the “next generation” of vegetable growers to network with each other while visiting west Michigan farms and is open to all growers in the Midwest. The tour will take place over two half days on July 17-18. Day one will focus on soil health, showcasing Morgan’s Compost and a major potato grower who is part of a soil health initiative. Day two will include another major potato grower plus muck vegetable production. There has been a lot of grower interest, so early registrations in the grower category are filling up fast. We are also offering a single-day option to allow for additional participants to caravan and leave on their own.

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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