North Dakota State University Extension Service - Burke County

Burke County AgAlert

Grasshopper Alert!

Field reports indicate that grasshoppers are increasing in numbers in the central and north central regions of North Dakota. Any crop is susceptible to attack from grasshoppers; however, later maturing crops are at very high risk now as early maturing crops are being harvested. 

Several conditions that favor a ‘grasshopper outbreak’ have occurred in 2008:

• Cool and wet early spring prevented premature grasshopper hatch and insured an adequate food supply.

• Warm and dry late spring promoted uniform hatching time and good weather conditions for feeding. 

• Hot summer with adequate rainfall in some areas of North Dakota has provided good food supply and low incidence of diseases.

A sweep net is an easy way to monitor for grasshoppers. In general, four 180-degree sweeps equals one square yard. Note that thresholds are different depending on whether you sample nymphs or adults, or whether you sample from the field margin or from inside the field. Grasshopper thresholds based on numbers of grasshoppers per square yard shown in the following

Grasshopper Thresholds: Infestation Ratings

One must be diligent scouting for grasshoppers this time of year because they are very mobile and will continue to be “on the move” during the harvest season.  The following table lists insecticides labeled for later maturing crops:

^aOnly Mustang Max was granted the Section 24C label in flax from July 24 through September 1, 2008.

^bDo NOT graze or feed areas treated with these insecticides.

^cOnly effective at controlling immature grasshoppers.

Note:  Mention of an insecticide does not constitute an endorsement or recommendation of the insecticide. Controlling mature grasshoppers is more difficult than immature grasshoppers and a higher rate may be necessary this time of year.  Please consult the 2008 ND Field Crop Insect Management Guide for rates: http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm

Dan Folske
Extension Agent/Burke County
Soil Conservation Technology Specialist
PO Box 280
Bowbells, North Dakota 58721
dan.folske@ndsu.edu
701-377-2927

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