Southeast Michigan vegetable regional report – August 17, 2016

Rain finally falls across southeast Michigan, though it may slow harvest efforts.

Tomato fruit impacted by bacterial canker. Also note necrosis and curling upward of leaf edges. Photo: Marissa Schuh, MSU Extension.
Tomato fruit impacted by bacterial canker. Also note necrosis and curling upward of leaf edges. Photo: Marissa Schuh, MSU Extension.


Widespread rain occurred over the weekend and into the beginning of this week. The wet and humid conditions, especially the widespread fog Monday and Wednesday morning, Aug. 15 and 17, are ideal conditions for the spread of many diseases, so be on the lookout for strange leaf lesions and molds. If you have any disease issues you want looked at or sent to Michigan State University Diagnostic Services, feel free to contact me at or 516-264-5309.

The table below presents rainfall (in inches) for the MSU Enviro-weather stations in southeast Michigan. Degree-day is base 50 degrees Fahrenheit since March 1 for 2016 and the range of degree-days at the same station in the last five years.

Rainfall and degree-day totals as of August 17, 2016


Rainfall last week

Rainfall since April 1


Five-year range






















Sweet corn and pepper growers should be aware that corn earworm is on the move in Michigan. If you have traps out, MSU Extension advises you to check them regularly. Pyrethroid insecticides should be sufficient for treatment.

A majority of the potato plants have been killed off and the potatoes are hardening underground. The Late Blight Risk Forecasting model is predicting that the wet and cool conditions this week may mean a greater risk of late blight in the area. When scouting for late blight, I’ve come across some botrytis blight, also known as gray mold or tan spot. This fungus can lead to lesions on the plant and premature plant death, which can impact potato quality and yield. If you are one of the growers who has gotten this year’s patchy rain, this could be yet another reason for lesions on leaves. For more information, see the Michigan Potato Diseases: Botrytis Blight fact sheet by MSU Extension.

Processing tomato harvest has begun, though the rainfall has made things muddy and flooding has made shipment of tomatoes difficult. Bacterial canker was reported in varieties planted in southern Michigan; if your tomatoes have black speckles or raised, white pimples with a bird’s eye appearance, they may have bacterial canker or another bacterial pathogen. Another symptom is leaves wilting on only the right or left side of the stem. For more information on spotting this disease and preventative measures to protect future tomatoes, see “Bacterial canker ravages processing tomatoes,” an MSU Extension article from 2011 that contains useful information and pictures.

Fresh market tomato growers on smaller farms have reported problems with tomato hornworm. While their large size can cause panic, they are primarily foliar feeders. If the tomato planting is smaller, removing hornworms by hand will be the most effective way of dealing with them. If there is more than one larvae per 10 plants in larger plantings, insecticide treatments are recommended. A wide variety of products work on tomato hornworms, though populations are often localized, so only spot treatments may be necessary. For more information, see “The tomato hornworm and the tobacco hornworm” by MSU Extension.

Watermelons are growing nicely and being harvested.

Pumpkins are doing well, though those in fields without irrigation in areas that have missed this year’s sporadic rainfall are struggling. Remember that pumpkins generally do not grow anymore after turning orange, and as plants age and lose leaves, the pumpkins themselves will need to be protected from the sun to prevent sunburn and rot.

Cucurbit growers should continue being vigilant and watch for downy mildew, which has now popped up in cucumbers in Macomb, Ingham and Clinton counties. This disease is most apparent early in the morning while dew is still present on the leaves; look for yellow patches on the leaf bounded by veins, and when the leaf is flipped over you will see the gray, fuzzy spores.


For those interested in learning more about soil health and getting hands-on experience with experts in the field, consider attending MSU Agriculture Innovation Day: Focus on Soils Aug. 24 at the Saginaw Valley Research and Extension Center in Frankenmuth, Michigan.

On Aug. 27, there will be a Breakfast on the Farm event in Hartland, Michigan. Tickets are free and can be picked up at various locations in southeast Michigan.

For growers interested in organic vegetable production and management techniques, the Zilke Farm in Milan, Michigan, will be hosting an Organic Vegetable Farm Twilight Meeting from 6-8 p.m. on Sept. 8.

For women involved with farms who want to increase their knowledge in regards to farm management and finance, Annie’s Project is offering classes at the Lenawee County Extension Office starting Sept. 15. For registration and more information, visit the Adrian Annie’s Project event page.

It’s never too early to make hotel accommodations for the Great Lakes Fruit, Vegetable and Farm Market Expo, Dec. 6-8, in Grand Rapids, Michigan. Hotel accommodations often sell out early, so make sure to make an early reservation so you don’t miss this year’s exciting program.

Did you find this article useful?