Crop Tech Corner

Got Stink Bugs? There's an App for That.

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Stink bugs are a growing menace for Midwest farmers. But with apps, scouting assistance and new insect predator research, scientists are doing their best to help out. (DTN photo by Nick Scalise)

ROCKVILLE, Md. (DTN) -- This bi-monthly column condenses the latest news in the field of crop technology, research and products.

NAME THAT (STINK) BUG

The University of Minnesota has released an app called the Midwest Stink Bug Assistant to help farmers quickly identify and report the invasive Brown Marmorated Stink Bug (BMSB) in their fields. This pest, which first crept into the eastern U.S. in the late 1990s, is becoming a serious pest of corn and soybeans in the Midwest, as well as fruits and ornamentals. The app allows growers to upload pictures they snap of questionable bugs. It features high-resolution photos of lookalike insects and graphics that highlight the BMSB's most distinctive features, to aid with identification. The app user can also submit a photo, using the app's "Report Invasive" option. An expert reviews the image and -- if it is confirmed as a BMSB -- adds it to a nationwide database tracking the pest's spread.

As a bonus, growers can also use the app to identify and report another new invasive pest -- the Bagrada Bug, which attacks vegetable crops like broccoli and cabbage.

The Midwest Stink Bug Assistant is free for both Apple and Android products. Apple users can download it here: https://itunes.apple.com/… and Android users can download it here: https://play.google.com/….

Read more about the app from the University of Minnesota here: http://blog-crop-news.extension.umn.edu/….

NEW SPRAY THRESHOLD FOR STINK BUGS IN CORN

As stink bugs have become a more permanent pest of corn, researchers are catching up to them. Recently, a North Carolina State University graduate student, Arun Babu, combed through the cornfields of eastern North Carolina and fine-tuned the scouting and threshold recommendations for this pest. Babu recommends scouting at least 100 plants scattered throughout the field, starting at the edges where stink bugs congregate, and moving toward the middle.

Babu has created two threshold tables for growers, each broken down into corn growth stages. The first table, called "partial plant sampling" allows growers to estimate the infestation as they scout, so they can decide quickly whether a field is in the danger zone or not. For example, if you are scouting a V4 cornfield and find 13 or more stink bugs before you reach 100 plants, you can stop scouting and plan to spray without finishing the field. The second table Babu developed is for a fully scouted field, and lists the percentages of infested plants at each growth stage that would trigger an insecticide application.

You can see the tables and their explanation here: https://entomology.ces.ncsu.edu/….

WASPS WITH STINKY TASTES (AND GRUESOME MANNERS)

And now for the good news! Stink bugs are almost universally reviled by humans and animals alike (chickens are a notable exception). They are also difficult to control with insecticides. Fortunately, there are a few parasitic wasp species out there that find them a delicious and convenient way to rear their young.

Scientists have honed in on one such species, a small parasitoid samurai wasp (Trissolcus japonicus), which lays its eggs inside stink bug eggs. Once the wasp larvae hatch, they feed on the eggs, emerge as adults and seek out more stink bug eggs to start the grisly cycle over again. With help from academic institutions, USDA is working to release this species of wasp in a number of states across the U.S. in hopes of providing a good biological control of stink bugs.

More recently, Oregon State University researchers have discovered another type of wasp, a soil-nesting species called Astata unicolor (A. unicolor), which also has a good appetite for stink bugs, and BMSB in particular. Unlike the samurai wasp, A. unicolor targets stink bugs in the nymph and adult life stages, but its methods are equally gruesome. The wasp first paralyzes its victim with a bite, and then spirits it away to a nest. There, the wasp lays its eggs in the stink bug, whose corpse serves as the hatched larvae's food supply. The Oregon scientists are hopeful that A. unicolor could someday be a good biological control of stink bugs, although its habitat is tricky to predict and encourage.

Read more about the new discovery of this soil-nesting wasp species here: https://entomologytoday.org/…

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee

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Emily Unglesbee