Two years of historic drought have left parts of Oklahoma and the region with an abundant supply of hungry grasshoppers, which is bad news for winter wheat and canola producers.
“A plague of grasshoppers means possibly significant damage to newly emerging wheat and canola, and these grasshoppers will eat until cold weather gives them permanent rest,” said Tom Royer, Oklahoma State University Cooperative Extension entomologist.
Fortunately, farmers have management options for grasshopper control.
A non-chemical option for wheat – but not canola – is to double-seed a 60-foot to 120-foot strip around the field margin. Grasshoppers will move into the field margin as other food sources are depleted.
“Double-seeded margins produce a thicker plant stand that can hold the foraging grasshoppers,” Royer said. “This allows the seedlings in the remainder of the field to establish themselves.”
Seed that is treated with imidacloprid (Gaucho), thiamethoxam (Cruiser) or clothianidin (Poncho) will reduce feeding damage from grasshoppers in both wheat and canola.
“Be aware that seed treatments will reduce damage from a moderate level of grasshopper infestation but won’t hold up under severe pressure by greater numbers,” Royer said. “Producers should use seed treatments at the highest registered rate to be most effective.”
Seed treatments also will reduce aphids in wheat and canola, as well as fall Hessian fly infestations in wheat. For more information, consult OSU Extension fact sheet CR-7088, “Effect of Planting Date and Seed Treatment on Diseases and Insect Pests of Wheat.” The fact sheet is available through all OSU Cooperative Extension county offices or online at http://osufacts.okstate.edu  via the Internet.
Apply a liquid or bait insecticide along the field margins at the time of seedling emergence.
“It may require up to a 150-foot wide band to get effective protection, plus a second application may be needed two to three weeks after the initial application,” Royer said. “Always check labels for grazing restrictions on any product selected.”
Grasshopper densities in Oklahoma vary with location, so producers should scout their fields prior to making a treatment decision. Numbers exceeding three to seven grasshoppers per square yard in a field or 11 to 20 grasshoppers per square yard in a field margin justify control. Also, grasshoppers will spread out and typically cause less damage as more wheat acres are planted.
“Although rain is in the forecast for parts of Oklahoma, it is still important to remember that hot, dry conditions will reduce residual activity of the insecticide, so a repeat application may be necessary,” Royer said. “Decisions will need to be made relative to local conditions.”
Royer added that producers seeking grasshopper control on wheat – but not canola – can combine options one and three.
As always, extreme infestations of grasshoppers are difficult to control. Additional information is available by consulting OSU Extension fact sheets EPP-7196, “Grasshopper Management in Rangeland, Pastures and Crops”; CR-7194, “Management of Insect and Mite Pests in Small Grains”; and CR-7667, “Management of Insect and Mite Pests in Canola.”