Michigan brown marmorated stink bug update – June 19, 2018
Brown marmorated stink bugs have been caught in traps and nymphs have been detected feeding on peaches.
For the past four weeks, members of the Michigan State University Extension fruit team have been monitoring for brown marmorated stink bugs in commercial apple and peach orchards. We think 2018 is going to be a big year for this pest, especially in southern Michigan. This is based on a combination of ever-increasing nuisance reports from urban to rural structures across Michigan, as well as what we have been seeing in traps and what scouts have been reporting in orchards.
This time of year, based on growing degree-days used in a model to predict adult brown marmorated stink bug activity and egglaying, eggs are hatching and second instar nymphs may be found feeding on young peaches. These nymphs are typically about a quarter or less of the size of adult stink bugs and appear dark brown to black with bands of white on their legs and antennae (see photo). Often, they will be found not far from the egg mass from which they emerged. In the photo, you can see the egg mass on the underside of the yellowed leaf.
Fresh evidence of damage will look like little beads of sugar water on the exterior of the fruit (see photo). Though these nymphs are small, they can do considerable early-season damage in peaches if not managed.
In addition to the other materials listed as effective against brown marmorated stink bug in tree fruit (see MSU Extension’s “2018 Michigan Fruit Management Guide,” E154), for the 2018 growing season, Michigan pome and stone fruit growers have a special use label (Section 18) for dinotefuran (sold as Venom or Scorpion) available to them. Contact your local MSU Extension fruit educator to obtain a copy of the label if you would like to use one of these products, as it is not yet posted to the Michigan Department of Agriculture and Rural Development website.
To know whether this pest is active in your orchard, use the limb-jarring method over a white sheet or tray and stink bugs will drop out of the tree onto the tray. Do this in trees at the edges of orchards next to woodlots and at the margins of orchards that had evidence of feeding damage last year. There is no threshold for triggering management using the limb-jarring method, but if you are finding nymphs or adults in orchard edges, use a material for your next cover spray that is also effective against brown marmorated stink bugs.
A threshold has been developed for brown marmorated stink bugs using traps baited with the Trécé dual lure. The recommendation is to count the number of nymphs and adults that accumulate in perimeter traps around a 10-acre or less orchard block, and when 10 brown marmorated stink bug nymphs or adults have been captured, that triggers a spray. Start the accumulation count over once a spray has been applied.