Michigan brown marmorated stink bug report for Aug. 1, 2017

Fruit and vegetable growers across the southern Lower Peninsula should be scouting and preparing to actively manage for brown marmorated stink bugs this season.

Key identifying features of brown marmorated stink bugs include a banded pattern along the abdomen and antennae with smooth, rounded shoulders. Photo by Jeff Wildonger, USDA-ARS-BIIR.

Key identifying features of brown marmorated stink bugs include a banded pattern along the abdomen and antennae with smooth, rounded shoulders. Photo by Jeff Wildonger, USDA-ARS-BIIR.

This is the first report of the Michigan State University Extension brown marmorated stink bug monitoring network for the 2017 growing season. Monitoring began in mid-May at some sites where brown marmorated stink bugs have been well-established, with new sites being added as the season progresses for a current total of 81 sites.

2017 MSU Extension Monitoring Network

Traps (see photos below) baited with a commercial lure are set up near apple, stone fruits (peach, plum, sweet and tart cherry), blueberry, grape, strawberry, a variety of vegetable crops and at several urban locations considered to be hotspots. Traps are up in all of the major specialty crop producing regions in Michigan (see table below).

Region in Michigan’s Lower Peninsula

Counties

Crops monitored in 2017

Northwest

Antrim, Benzie, Grand Traverse, Leelanau

Apple, cherry (sweet and tart), grape (wine and juice)

West central

Mason, Oceana

Apple, peach, pepper

Fruit Ridge

Ionia, Kent, Montcalm, Muskegon, Ottawa

Apple, blueberry, cherry (sweet), grape

Southwest

Allegan, Berrien, Ottawa, St. Joseph, Van Buren

Apple, blueberry, cherry (sweet and tart), grape, peach, plum, pumpkin, strawberry, raspberry

Southeast

Genesee, Ingham, Lapeer, Lenawee, Livingston, Macomb, Monroe, Saginaw, Washtenaw

Apple, cherry (sweet), grape, peach, pepper, soybean, tomatoes

Results so far

At this time last season, we had caught a total of 30 brown marmorated stink bugs. This season, we have already captured 190 brown marmorated stink bugs across the entire network with the majority of brown marmorated stink bugs found in traps in orchards and vineyards in the southwest part of Michigan. However, the average number of brown marmorated stink bugs caught in traps in any region is still well below one per trap per week. That said, growers of vulnerable crops need to monitor for this pest themselves since local populations can still be highly variable and especially in blocks where there was suspected crop injury in 2016.

While adult brown marmorated stink bugs have been captured in traps since May, nymphs have started being caught at a few sites within the last few weeks. Both nymphs and adults can injure crops when they feed on fruit, pods, nuts, or seeds.

Biology and lifecycle of brown marmorated stink bugs

Brown marmorated stink bug adults emerge from overwintering sites (e.g., woodlots, manmade structures) in response to a day length of 13.5 hours, which is late April in Michigan. Egglaying begins after 135 growing degree-days (GDD equals base 57.2 degrees Fahrenheit) have accumulated, around the end of May. Females lay clusters of up to 28 greenish-white eggs on the undersides of leaves of preferred host plants, and between 10-20 egg clusters in their lifetime.

Feeding and development continue through five nymphal stages before molting into the adult stage in late July or early August. High densities of brown marmorated stink bugs and the potential for damage become more likely at this time. The summer generation continues to feed before moving to overwintering sites beginning in early September through November. The adult produces an attractant, called an aggregation pheromone, which attracts other adults to the same location. This is why clusters of adults can be found gathering on buildings. One generation is thought to occur in Michigan.

Trapping for nymphs and adults

While brown marmorated stink bugs are fairly easy to identify and distinguish from native stink bugs, they can be highly cryptic because they prefer the tops of trees and their coloring exactly matches tree trunks. Traps are easy to deploy and check, but the area of influence for a single baited trap appears to be relatively small, and not terribly efficient. Therefore, it is best to place traps so brown marmorated stink bugs are intercepted as they move between habitats.

Traps

Several different kinds of traps are available (see photos below). Most tend to have a pyramid shape with fins that need to either touch the ground or be attached to a tree trunk or post in such a way so nymphs and adults can walk up into them. There is also a new, clear, sticky panel trap that can be attached to a tall stake. All of these traps must be paired with lures.

Brown marmorated stink bug diagram

Examples of traps used to monitor for brown marmorated stink bugs: pyramid (left), Rescue brand (middle) and a clear sticky panel (right).

Lures

Lures are meant to be attractive to nymphs and adults. Several commercial lures are available, but all of them appear to have a relatively limited range of attraction. In other words, brown marmorated stink bugs need to be in the vicinity in order to pick up on the scent. Follow the manufacturer’s recommendation for how often to replace lures.

Making the most of brown marmorated stink bug traps

Traps are used to intercept brown marmorated stink bugs as they move among different host plant habitats and to guide decisions about when to apply insecticide. In orchards, use six traps per every 10 acres, with four traps placed around the perimeter and two traps placed in the interior where damage has been detected previously or is otherwise considered to be at high risk of damage. Check traps, at minimum, once per week.

Other monitoring techniques

Visually inspect field or orchard edges for crop injury or the insects themselves. In tree crops like apples and peaches, limb-jarring upper branches over a white sheet can help determine if brown marmorated stink bugs or other stink bugs are present.

Host plant preferences

The list of plants on which brown marmorated stink bugs will feed is long, including many wild, agricultural and ornamental plants (see table below). Preferred hosts are non-native ornamental trees and shrubs that bear seed pods or fruit, but they will also feed on and damage herbaceous fruiting plants. Brown marmorated stink bugs move in and out of different crops over the course of a season, therefore it is useful to know whether other high risk crops and ornamentals are near your vulnerable crop when considering where to focus monitoring efforts. Woodlands are thought to be important overwintering sites and as a non-crop food source.

Relative risk of damage by brown marmorated stink bugs to Michigan specialty crops, field crops and ornamental or non-crop trees and shrubs.

Risk level

Tree fruit and nuts

Berries and grapes

Vegetables

Field crops

Ornamental or non-crop trees and shrubs

High

Apple, Hazelnut, Nectarine, Peach1, Pear (Asian and European)

Grape2

Beans (green, pole, snap), Edamame, Eggplant, Okra, Peppers, Sweet corn, Swiss chard, Tomato

Dry beans, Field corn, Soybeans, Sunflowers

Black cherry, Catalpa, Crab apple, English holly (female), Japanese pagoda tree, Multiflora rose4, Redbud, Tree of heaven4, Wild brambles4

Moderate

Apricot, Cherry2 (sweet and tart), Plum, Walnut

Blackberry, Blueberry2,3, Raspberry

 

Asparagus, Broccoli, Cauliflower, Collard, Cucumber, Horseradish, Lima bean, Tomatillo

Winter wheat5

Black walnut, Flowering dogwood, Littleleaf linden, Maples, Serviceberry

Low

Not available

Cranberry, Strawberry

Carrot, Garlic, Kohlrabi, Leeks, Lettuce, Onion, Potato, Spinach, Sweet potato, Turnip

Not available

Blackgum, Ginkgo, Japanese maple, Kousa dogwood

1 Additional risk potential due to bark feeding.
2 Potential risk of taint/contamination.
3 Considered moderate to high risk.
4 Considered to be a particularly attractive and important host plant.
5 Considered to be a population source more than a crop damaged by brown marmorated stink bugs.

For more information about management strategies in fruit:

For more information about management in vegetable crops:

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