Soybean School: Grasshoppers thrive in dry conditions

(Kara Oosterhuis/RealAgriculture)

Grasshoppers have proven to love Manitoba soybeans this season, and producers are starting to get anxious.

With harvest approaching, it’s important to know the difference between grasshoppers that are pests and which ones aren’t, and to keep an eye on the pre-harvest intervals on products if a grower decides it’s economical to spray.

As John Gavloski, provincial entomologist with Manitoba Agriculture, explains in this Soybean School, the main pest species farmers should be aware of is the two-striped grasshopper.

“It’s got two stripes that start right behind the eye, and they come right to the back of the wings,” says Gavloski. “They can come in both brown and green, and [when fully developed] they can fly.”

When it comes to controlling the hoppers, Gavloski suggests bran baits and various insecticides. However, he notes that while baits will have some control over the adults, it has a higher control rate on juvenile grasshoppers.

“As a juvenile, one or two flakes will kill the grasshopper. As an adult, it’s about four or five flakes, so higher rates are needed.” (Story continues below)

To learn more about grasshoppers stages, residuals, and other potential control options, check out this Soybean School filmed at Crops-A-Palooza in Carberry, Man.:

When deciding whether or not to spray your crop, Gavloski emphasizes that you have to keep an eye on the pre-harvest intervals.

“Some products, you just can’t use them when we get into late July and August because the pre-harvest intervals are just too long,” he notes, while adding that there is another technique that producers can use for spraying: reduced agent-area treatments. It’s a strategy for broadacre crops, versus fruits or vegetables.  “The way this works is instead of spraying [the whole field], you will spray in strips. You do a pass that’s treated, and a pass that’s non-treated.”

As far as pressure goes for this year, Gavloski says it has been moderately high. “We have had worse years, so I won’t call it an outbreak, but there are certainly very high levels, and there has been a lot of spraying.”

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