Grasshopper Control

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Organizing a Grasshopper Control Program

 
  Early spring is the time to start scouting for grasshopper nymphs. They were easy to find in 2008 and 2009.
 
  Mated female grasshoppers lay eggs in the fall in undisturbed soil.
 
  GIS maps outlined fields to be treated with insecticide.

For farmers and ranchers who depend on their land’s productivity to stay in business, grasshoppers can be economically devastating. Control options are highly dependent on the balance between cost and effectiveness versus the economic loss of the crop or land use. For grasshoppers, the per-acre cost of control decreases and the effectiveness increases when large blocks of land are treated. Therefore, organizing groups of landowners to implement management improves the economics of grasshopper control.

Not only are grasshoppers voracious, but they also clip and drop green forage material, making it unavailable as range food. In a 10-acre field, for example, a density of eight grasshoppers per square yard can clip and consume enough forage in one season to feed a cow for one year (Hewitt 1977). The USDA-recommended action threshold for stockable rangeland is nine adults and/or late instar nymphs per square yard. Because grasshoppers are more susceptible to chemical control in the early nymphal stages, the Utah Department of Agriculture and Food considers chemical control justified when populations reach eight or more nymphs per square yard.

In fall 2008, the Extension offices in Duchesne and Uintah Counties were receiving calls about heavy grasshopper infestations. These calls led to fall scouting of infested areas to estimate the number of adults laying eggs.

Our scouting efforts discovered a high number of egg-laying adults, which meant that there could be a heavy grasshopper infestation in 2009. County Commissions, FSA Committees and Conservation District Boards were informed of the fall situation. We organized community meetings in early spring 2009 to spread the word of the possible devastation a large grasshopper infestation could have on forage and gardens. Another purpose of the meetings was to teach participants how to scout for grasshoppers, estimate densities, and chemical control options.

Grasshopper densities are reported as numbers of grasshoppers (all species combined) per square yard. The technique most commonly used for these estimates requires the surveyor to count the number of grasshoppers fleeing an estimated one-squarefoot area approximately 10-15
feet ahead (USDA, undated). The surveyor repeats this procedure 18 times per sample location, adds the 18 observations, and divides by two to determine the numbers of grasshoppers per sq. yard.
 

Producers in selected areas of possible heavy infestations were solicited to help in early scouting. When producers found high densities of grasshopper nymphs, they organized meetings to determine acreage infested and who might be interested in participating in a control program. After those meetings, we met with the representative producers and County Commissioners to inform them of the problem and to see if the county would be willing to help in the control program. The counties agreed to conduct GIS mapping and to serve as liaison between producers, the pesticide applicators, and the State of Utah. County attorneys prepared contracts for individual producers in which they agreed to pay their portion of the spray bill.

County GIS personnel created maps of producer fields that needed to be sprayed, which were used by the pilots applying the grasshopper insecticide. The growth regulator, Dimilin (diflubenzuron), was applied using the “reduced agent and area treatment method”, or RAATs.

Over 59,000 acres were sprayed representing 304 individual producers. Duchesne County paid the grasshopper spray bill of $136,766.50 while Uintah County paid $29,433.00. UDAF reimbursed 90%, and producers reimbursed 10% of the total bill. There was a 78% estimated average kill based on post-spray survey of the originally-scouted acres. Overall success of the program was attributed to a combination of factors including organization of large numbers of landowners, the participation of the counties, and the technical aspects of the mapping and spraying.

In 2010 and 2011, we conducted grasshopper scouting and landowners implemented their own control measures and submitted paperwork to the state for reimbursement. The success of the large effort in 2009 was evident in the reduced grasshopper numbers in both 2010 and 2011.



References:

 

Hewitt, G.B. 1977. Review of forage losses caused by rangeland grasshoppers. USDA Miscellaneous Publication 1348, 24 pp.

U.S. Department of Agriculture. Undated. Grasshopper survey, a species field guide. USDA, APHIS, PPQ.



-Boyd Kitchen, Extension Associate Professor, County Director for Uintah and Daggett Counties,
and Troy Cooper, Extension Associate Professor, County Director for Duchesne County.