East Michigan vegetable update – June 24, 2020

Crop progress is going well overall with some specific issues on individual farms.

bare ground peppers freshly cultivated
Macomb County bare ground peppers freshly cultivated. Photo by Ben Phillips, MSU Extension.


Rainfall across the region over the last week was between 0 and 0.25 inches.

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)


Overwintering generation start to emerge and lay eggs

450 (occurred June 6)

Peak flight and egg laying of overwintering generation

700 (predicted to occur June 20)

Peak flight and egg laying of first generation


Peak flight and egg laying of second generation



I looked at last year’s report for this time and other than crop progress being much more normal, pest pressure is very similar.

Stemphylium and Alternaria symptoms can be found in transplanted sweet onions.

Moisture stress in garlic is starting to yellow the leaves.

European corn borer began its peak egglaying phase this week. Sweet corn over the V6 stage will be susceptible to them.

Cucumber beetle is being reported in high numbers on pumpkins, squash, melons, watermelons and cucumbers with untreated seed.

Cercospora leaf spot and Alternaria leaf spot have both been showing up in Ontario red beets.

Cucurbit downy mildew has been found on plants in Berrien County, two weeks after spores were first trapped there. Spores were also trapped in Bay County and Saginaw county since June 16, but no symptomatic plants have been found here yet. Given the appearance in the state, conditions are favorable and growers should consider starting up their preventative protectant sprays on melons and cucumbers. On small plants, growers may be able to use banded applications.

Zebra caterpillars are on some cole crops plantings.

Fourlined plant bug is ravaging herbs in some places.

Tarnished plant bug can be found now.

Japanese beetles are out.

Crop progress

Asparagus is being renovated for fern out.

Strawberries are picking strong but berry size is smaller than what some growers were hoping for due to moisture stress. Renovation will begin soon.

Cole crops that experienced vernalization temperatures this spring will be bolting around now. I have not seen any flowers except on radish. Broccoli curds are forming and are about the size of a baseball. I have not seen cauliflower at this stage yet but it is probably there somewhere. That is the time when tying takes place to keep the heads white. No need for this with the colored varieties.

I have heard reports of collards/kale going to seed this week. If transplants were in the ground with at least four leaves before those freezes on May 9 –12, then they may have accumulated enough vernalizing time (three to five weeks) in the range of 32 to 55 F.

Root crops are being harvested. I also received reports of radishes bolting this week. They can vernalize as soon as seed germinates, and as quickly as one week with temperatures between 32 and 59 F. So, I went through hourly weather data to see how quickly they would have accumulated a week’s worth of vernalizing time based on their planting dates. Plantings between May 6 and 11 received one week of vernalizing time within 10 to 12 days with no devernalizing temperatures above 68 F to subtract from that. Plantings after May 13 received a week’s worth of vernalization temperatures within seven days of planting, but had about 4.5 days of time above 68 F that could be subtracted, leaving only two days of vernalizing time. All plantings after May 13 have not bolted.

Early transplanted sweet onions are golf ball size. Seeded onions are about the diameter of a $0.25 piece.

Melons and cucumbers are flowering across the region. Watermelons are close behind.

Summer squash in field plantings are just starting to bloom in some fields if they were transplanted early. The hoop house crops of squash are being harvested.

Peppers and eggplants early fields have first fruit set and are about 1 foot tall. Some planting is still going on.

Tomatoes in the field are just beginning to flower. Stakes are in and the first level of strings have been tied. I’ve been getting lots of questions about pruning field-planting indeterminate tomatoes.

In a lean and lower tomato greenhouse system, these plants are pruned down to one leader and attached to a hangar spool on the ceiling. The single leader is allowed to grow as long as possible because flowers come directly off of the main stem. So, more stem equals more flowers. All other suckers are cut to keep the plant focusing its resources on the one stem and to maintain airflow in what could otherwise be a stifling jungle of leaves.

On a single stem, the flowers appear higher up the stem as it grows and this is why greenhouse growers use hangar spools of string to lower the vine and pull it to the side to keep a comfortable picking height. This practice is similar for all types of indeterminate tomatoes grown in a greenhouse, from cherries to beefsteaks. The high value space and the availability of a strong ceiling are what drive that system.

For field produced indeterminate tomatoes, stakes need to be 8 to 10 feet tall above the ground to support the plant. About half of the plant’s fruit production will occur above 5 feet. Without a strong ceiling, you are relying on the strength of the stakes and trellis string to brace against the wind. When plants get large, they make good sails.

Some growers sink a tall pole for each tomato and tie the tomato to the pole as it grows. Others pound a stake every three or four plants and fasten a rail or top wire across the top of the stakes along the row, and even between the rows to strengthen the support. Anchor stakes to tension and tie off the top wire at the end of each row are also common. Basket weaves can be harder to accomplish as plants get higher, but with top rails or wires, you can tie vertical string supports similar to in a greenhouse or use horticultural netting. Leaning and lowering outdoor indeterminate tomatoes would seem possible with a top wire, but the wind may undo your efforts. Field plantings are much better ventilated.

If fields are much more ventilated, should the number of leaders be the same? This takes a little experience to judge and is variety dependent. Leave cherry and grape types alone. For larger fruited plants, pay attention to vigor. If your tomato’s anatomy has a low vigor plant, focus the plant’s resources on one leader and prune the rest below the first flower cluster. For a medium vigor plant, leave two to three leaders below the first flower cluster. For a high vigor plant or a block that is on plastic with irrigation and a good fertilizer program, leave four to six leaders below the first flower cluster. Basically, by leaving more leaders on a more vigorous plant, you are taxing its vegetative resources and prompting it to produce more flowers on more stems.

Once this initial pruning has been completed and flowers are being produced, the plant will not spend much more energy to fully develop more suckers. Suckers at that point will become small branches and not big bully stems. If you do not prune at all, the plant will spend a lot of energy and time developing more than six leaders before committing to flowering. This makes for a densely crowded planting, a delayed harvest and smaller fruits who have to share the remaining energy of the plant after all that vegetative growth and fruitset.

About a month before first frost, field-planted indeterminate plantings can be “topped” to remove the growing tips of the main leaders. This will focus the plant’s resources on ripening fruit. Similar to how topping Brussels sprouts bulks up the side sprouts on the stem.

Great Lakes Vegetable Producer’s Network

MSU Extension is participating in a live, weekly roundtable discussion during the growing season for commercial vegetable producers in the Great Lakes and Midwest region. Join us! We broadcast live via Zoom at 12:30 p.m. ET/11:30 a.m. CT every Wednesday from the first week of May to the first week of September. Listen live or later. If you have a pressing vegetable production issue that you would like discussed, simply email it, along with your phone number, to greatlakesvegwg@gmail.com 

Next week, July 1: Getting Elemental with Boron

“Preparing your farm for tax season now” online program

Held July 17 from 12-1 p.m. via Zoom, the goal of this program is to help farmers who do not have a good recordkeeping system in place but are not ready to buy an accounting software, or hate computers, or love spreadsheets. Want to take the next step beyond keeping records in a shoebox and get your records straight using something like the farm records book in preparation for the next tax season? Then register for this program at: Prepare Your Farm For Tax Season Now - Online Workshop.

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 Plant & Pest Diagnostics.

Did you find this article useful?