Southeast Michigan vegetable update – Aug. 9 2017

Harvest continues and pest pressure remains low.

Brown marmorated stink bugs have a brown, shield-shaped body with black and white banding along both their rear end and antennae. Photo by Marissa Schuh, MSU Extension.

Brown marmorated stink bugs have a brown, shield-shaped body with black and white banding along both their rear end and antennae. Photo by Marissa Schuh, MSU Extension.

Weather

The current cool and dry weather pattern will likely hold through the end of this week and into next. There is a chance for small amounts of rain Friday, Aug. 11. While moisture from humidity and rain is minimal, the low, overnight temperatures are usually reaching the dew point, and the resulting leaf wetness can still allow foliar diseases to flourish.

The table below presents rainfall in inches for the Michigan State University Enviroweather stations in southeast Michigan with the amount of change from last week reported. Growing degree-days (GDD) starting March 1 are calculated using the Baskerville-Emin Method.

Rainfall and GDD totals as of Aug. 9, 2017

Enviroweather Station

GGD base 50

Five-year GGD average base 50

Rainfall since April 1 (inches)

Commerce

1,700 (+104)

1754.2

11.9 (+2.38)

Deerfield

1,972 (+120)

Not available

12.23 (+0.52)

Hudson

1,767 (+105)

1914.2

13.21 (+0.5)

Pests

A new pest to be aware of is brown marmorated stink bug, a pest capable of feeding on a wide range of crops. You’ve likely seen these large, brown insects in your home, which is where this pest overwinters. This year’s batch of stink bugs are starting to be caught in traps, and some damage in apples has been reported in our part of the state.

I am trapping for brown marmorated stink bugs in tomatoes in Lenawee and Washtenaw counties, and while I haven’t caught any, these traps only reflect a limited area. The vegetables most at risk include beans, eggplant, peppers, sweet corn and tomatoes. In sweet corn, the damage causes kernels to collapse and discolor areas, while in fruiting vegetables white or yellow areas of spongy tissue are found in areas where feeding has occurred.

For pictures of damage in all at-risk vegetables, see “Integrated Pest Management for Brown Marmorated Stink Bug in Vegetables” from Stop BMSB. For more information on brown marmorated stink bug biology and their current status in Michigan, see the MSU Extension article, “Michigan brown marmorated stink bug report for Aug. 1, 2017.”

Crops

Broccoli and cauliflower are being harvested.

I’ve heard some reports of thrips in cabbage, which happens when thrips move from small grains or grassy areas into other crops as things get dry or the area they were inhabiting is harvested or mowed. The key to controlling this pest is the right product at the right time. An effective product needs to be used and on the plant before thrips can enter the head, where they can cause damage without being hit by insecticides.

There are a few products labelled for thrips in cabbage. Trials in Ohio found Radiant to be effective, according to “Vegetable Insecticide Update” by Ohio State University. For a full listing of products, see the “Midwest Vegetable Production Guide,” and if this is a consistent problem, consider planting a thrips-tolerant variety.

Eggplant is being harvested and reports of verticillium wilt continue to roll in. Growers producing some of the less traditional, non-Italian varieties report good market sales. While white, lavender and striped varieties may produce fewer or smaller eggplants than the typical Italian variety, these eggplants are often less common at markets and can sell quickly for a good price, though their success will depend on your market.

Muskmelons are being harvested.

Onions are being harvested.

More pepper fields are being harvested. Good yields and quality are being reported.

My European corn borer traps all captured zero moths this week, and the MSU Enviroweather model for this pest suggests the moths have stopped flying in our region.

Pumpkins and winter squash continue to size up. Squash bugs are still in the nymph stage in some fields; taking care of these guys now is much easier than taking care of them later. See the Midwest Vegetable Guide for a list of recommended products.

I’ve seen aphids present in low numbers in some fields, as well as some sporadic virus symptoms. Treating aphids because they are a nuisance or because they spread viruses is tricky, as they are often controlled by natural enemies and sprays can wipe out the local population of predatory insects.

When you’re in your field, look for aphid colonies with mummified aphids as well as nearby ladybeetles, minute pirate bugs and other natural enemies. If these predators are near aphid colonies, they are feeding on the aphids and will likely bring their population numbers under control.

aphid colony

In this aphid colony, the three large, white aphids have been mummified, meaning a parasitic wasp has laid eggs inside the aphid. The wasp larvae consume the aphid from the inside, the aphid dies over the course of a few days, and a new generation of parasitic wasps emerge, starting the cycle over again. Photo by Alton N. Sparks, Jr., University of Georgia, Bugwood.org

On the disease front, make sure preventative fungicides for powdery mildew are being applied. Recent work in Ohio found Approvia Top, Inspire Super, Procure, Quintec and Rally to provide very good control of powdery mildew, according to “Cucurbit Powdery Mildew: A Little Late this Year but Start Scouting Now” by Ohio State University. The “Midwest Vegetable Production Guide” has a bigger list of recommended products. When evaluating your program, alternate between products with different FRAC groups and apply products tank-mixed with Bravo and a surfactant when appropriate.

Sweet corn harvest in ongoing. Corn earworm populations continue to be low, with less than 15 moths being captured over the course of the last week in my traps in Lenawee and Monroe counties. Western bean cutworm catches are low, with less than 10 a week in my traps in Lenawee, Monroe and Washtenaw counties, suggesting the peak of this pest has passed.

Cooler temperatures over the last week will likely cause gray wall in tomatoes. This condition causes tomatoes to have yellow blotches and streaks that never ripen, and when the tomato is cut in half width-wise, this yellow area will have darkened vascular tissue. This is generally seen when tomatoes are exposed first to warm, sunny weather and then to cooler, cloudy weather.

Staked tomatoes are being harvested. I’ve heard some complaints about small tomatoes, which are typically caused by either hot weather or dry conditions; the latter is likely the case in our area.

Processing tomatoes are being sprayed with ethylene as ripe, green tomatoes are found. Harvest will begin in the next week on most operations.

Smaller, specialty varieties of watermelon are being harvested.

Contact me any time at 517-264-5309 or .(JavaScript must be enabled to view this email address) for pest or disease sampling. I make updates regularly on Twitter at @SoutheastMIVeg.

Meetings

The Small Farm Pest Management: Informed Decisions and Sustainable Approaches field day on Aug. 13 in Ann Arbor, Michigan, will cover integrated pest management practices that can be utilized to control insects in vegetable systems.

Growers with greenhouse and floriculture aspects to their farms may be interested in the attending the 2017 Greenhouse Production, Plant Health, and Marketing Conference Sept. 13 in Lansing, Michigan. A wide range of topics will be covered, with a focus on increasing plant quality, safety and sales. For more information, see “Register now for 2017 Greenhouse Production, Plant Health and Marketing Conference.”

The Midwest Mechanical Weed Control Field Day is Sept. 26 at the MSU Horticulture Farm. This meeting will feature mechanical weeders from the U.S. and Europe, as well as the experiences of farmers who use these tools. For more information and registration, see “Midwest Mechanical Weed Control Field Day.”

Hotels are filling up for the Great Lakes Fruit and Vegetable EXPO, Dec. 5-7 in Grand Rapids, Michigan. The combination of grower-focused, research-backed presentations and an amazing exhibit hall make it a can’t-miss event. 

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