East Michigan vegetable regional report – August 5, 2015

Much needed water but mild temperatures do not favor our warm-season crops.

This is not pepper maggot, but the picture demonstrates the mimicry between a similar species and a jumping spider. Photos from “A Sheep in Wolf's Clothing: Tephritid Flies Mimic Spider Predators,” Mather MH, Roitberg BD
This is not pepper maggot, but the picture demonstrates the mimicry between a similar species and a jumping spider. Photos from “A Sheep in Wolf's Clothing: Tephritid Flies Mimic Spider Predators,” Mather MH, Roitberg BD


The weather system that came through on Sunday-Monday, Aug. 2-3, brought some much needed water, ranging between 1 and 2.5 inches across the region. This put the east side pretty close to the five-year average for rainfall accumulation for this week. However, the weather system came from the northwest and brought cool air with it, which we will be sitting with us for the rest of the week. Re-apply fungicides to stay covered in this mild weather.

It is good to hear from readers. Thanks for calling.

I had the opportunity to visit some beautiful food gardens in Lansing, Michigan, coordinated by John Krohn, at the Ingham County Land Bank. Krohn is doing a fine job negotiating city water supplies, mulch acquisition, composting and hugelkulturing dead trees in abandoned lots, and demonstrating plasticulture and fertigation to vegetable newbies. (Hugelkulturing is a composting process employing raised planting beds constructed on top of decaying wood debris or other compostable biomass plant material.) They are producing high quality okra and garlic at commercial market-garden scale. Morale is high and everyone is pretty much on the same page, which is rare in these community endeavors. Must be doing something right. One direction they want to move into is the production of bulk organic transplants.

Here are the rainfall and growing degree day (GDD) base 50 degrees Fahrenheit accumulations to date from Michigan State University Enviro-weather stations.

Rainfall and GDD summary


GDD (50 F, March 1)

Rainfall (inches, April 1)


1,503 (174.4 behind average)

10.93 (1.98 since last week)


1,607 (197 behind average)

11.21 (2.55 since last week)


1,588 (194.1 behind average)

14.51 (1.96 since last week)


1,576 (213.9 behind average)

13.41 (1.04 since last week)


Carrots are sizing up nicely. Aster leafhopper catches have increased on the west side of the state, but infectivity remains low.

Sweet corn harvest continues. Corn earworm has been captured at a rate of one moth per night in Michigan’s Bay area. This warrants insecticide applications every five days in silking corn. Western bean cutworm catch has been increasing rapidly.

Many cucumber and pickle plantings are crashing hard. Every cucumber plant I have seen in the last week has downy mildew. The map of confirmed counties now includes most of Michigan’s east side, and one can assume that every county east of US-127 has downy mildew.

Melons and watermelons should be scouted and protected from downy mildew as well. They are quite susceptible and high value.

The first plantings of squash are out, and the second plantings will be producing soon. There have been some virus symptoms found in the Bay area, even with low aphid populations. Michigan State University vegetable entomologist Zsofia Szendrei has reported a spike in aphid numbers caught in suction traps deployed across the state. Virus infections of squash plants could start showing up with the recent blow-in of aphids. It is worth scouting for, but systemics should not be applied close to harvest or flowering.

Pumpkin hobbyists are having trouble with a variety of things, including lack of pre-plant broadcast nitrogen (N), forgetting or neglecting to sidedress with any additional N, inappropriate crop rotation distances and time-frames, and deer browse. Michigan State University Extension recommends getting about 20-30 percent, or 40 pounds, of N down pre-plant, and then follow up with the remaining percentage of your soil test recommendation in one or two follow up applications.

Root rots and cucumber beetle pressure can be exacerbated when pumpkins follow pumpkins year after year. In addition, deer herds can get used to that resource and will browse young pumpkin fruits heavily if action is not taken. Some growers invest in fencing where deer populations are perennially high, while others rely on spray-on repellents. As summarized in an Alabama Extension bulletin, there is a wide range in price and ingredients of these deer repellents. Like birds, deer herds can get used to particular approaches, and growers should pair repellents with other harassment techniques. If you need more protein in your diet, check out this guide to lethal control of birds and mammals in Michigan farm fields.

Cauliflower, broccoli and cabbage were seeded and transplanted for fall harvests over the last couple of weeks. MSU is very interested in hearing if any of your cole crops go blind this year. There seems to be a pattern showing up on the east side, and it could be important to take a closer look at the crops that are scarred and twisted.

Field tomatoes and peppers are being harvested. Growers should be judiciously applying protectant fungicides for late blight. Please see “Tomato Late Blight Fungicide Recommendations 2014” or MSU Extension Bulletin 0312, “2015 Insect, Disease and Nematode Control for Commercial Vegetables,” for a listing of registered fungicides. Like downy mildew in cucumbers, this is fast, deadly to plants and early this year.  

I received a report from my colleague in Macomb County that a pest is starting to show up consistently in organic peppers. The pepper maggot is a small, picture-winged fruit fly that lays its eggs on the skin of round and blocky-shaped pepper and eggplant fruit. The larvae burrow into the fruit and feed on the inside. You can identify its presence through discolored spots on the fruit and maggots inside, and the adult flies on your plants. Picture-winged fruit flies have stripes on their wings that mimic the leg-arrangement of jumping spiders (see photo). This protects the flies from being attacked from behind, like jungle-dwelling humans wearing a reverse mask to trick big cats into thinking they’ve been spotted. Their damage differs from European corn borer because they don’t leave burrowing holes. European corn borer also burrows up near the cap.

Pepper maggots can be controlled with the same systemic insecticides used for European corn borers, and commercial conventional growers are probably controlling it already. Gardeners and commercial organic producers should keep an eye out because Bt won’t work on these flies, and eggs and larvae can’t be controlled with sprays because they are inside the fruit from the beginning.

Onions just look fantastic where weed control has been good. MSU weed specialist Bernie Zandstra has some tips for onion growers in these wetter and cooler years. Thrips populations multiplied in last week’s hot weather. Growers should be thinking about an application of Radiant.

Please contact me at phill406@msu.edu or 989-758-2502 to pick up any suspected disease samples, or send the diseased plant parts to MSU Diagnostic Services.

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