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Wheat growers need to consider options to manage grasshopper problemsNebraska Grasshoppers have been plentiful in many parts of Nebraska this year. With the upcoming planting of winter wheat, growers need to consider their options to manage grasshoppers this fall. Grasshopper populations decline through late summer and fall. However, they remain significant enough until the first hard freeze to threaten wheat seedlings as they emerge, said Gary Hein, University of Nebraska-Lincoln entomologist at the Panhandle Research and Extension Center at Scottsbluff. "Emerging winter wheat has very limited foliage. Grasshoppers can easily keep the wheat clipped back completely, causing stand losses in the field margins," Hein said. "Growers need to monitor grasshopper densities in areas surrounding wheat fields." Normal threshold densities in areas surrounding cropland need to be lowered because of damage potential. Densities in the range of 11 to 20 per square yard in non-crop borders surrounding newly planted wheat fields may be enough to cause significant loss, Hein said. Although grasshopper damage potential decreases into the fall, if grasshopper densities are extreme it is difficult to completely eliminate the damage. Several options are available to help reduce the risk and/or manage developing problems, Hein said. "Early planting should be avoided in areas of high grasshopper activity to reduce damage potential," Hein said. "Planting high risk fields near the end of the optimum planting window will reduce the time period that a field will need to be protected from grasshoppers in the fall." In addition, growers should increase the seeding density of wheat in field margins to compensate for partial stand loss. This may allow for a reasonable stand after grasshopper damage has run its course, Hein said. "If grasshopper populations surrounding wheat fields are high, insecticide control may be necessary to reduce their impact," Hein said. Controlling adult grasshoppers is difficult, but several options are available including: planting time application or seed treatments to field margins or treatments of surrounding borders to protect the wheat as it is emerging. More detailed information about grasshopper control, including information about insecticides, can be found in Crop Watch, UNL Extension's crop production newsletter, at http://cropwatch.unl.edu/archives/2008/crop21/grasshoppers.htm. "Grasshopper control around wheat fields can be challenging and the level of effectiveness for any control option will depend largely on the density of grasshoppers," Hein said. "Under very heavy pressure none of the control options will be completely effective, and the loss of some stand on the field margins may be inevitable. Grasshopper control in winter wheat really will be a compromise between effective control and affordability." If grasshopper damage reduces stand in the field margins, growers can replant these areas in the fall after the first hard freeze and grasshopper populations have declined, Hein said. 9/22/08 Date: 9/17/08
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