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What are the effects of the infestation?

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As most people know, grasshoppers have infested areas of Routt County, which could likely lead to the devastation of farmers' and ranchers' fields. We asked C.J. Mucklow, Routt County agriculture extension agent, what caused the infestation, what kind of damage the grasshoppers can do and how residents can combat the problem.


Q. Where are the grasshoppers, how many are there, and what are the dominant species in this area? How many grasshoppers are usually in this area?

A. There are commonly grasshoppers all over the county each year, but they rarely reach infestation levels as high as this year. The U.S. Department of Agriculture Animal and Plant Health Inspection Service surveyed the infestation and found levels of grasshoppers ranging from 120 to 180 per square yard. Grasshoppers are not considered a threat to crops unless they exceed 10 to 20 grasshoppers per square yard. Normally grasshoppers don't exceed these levels in any given year. The infestation that's been surveyed or reported to date includes areas west of Steamboat Springs south to Humble Ranch on County Road 14 and north to C.R. 56 in the Deep Creek area east to approximately the Steamboat Springs Airport and as far west as the confluence of the Yampa and Elk rivers. Additional scattered infestations have been reported in West Routt near Hayden. According to USDA-APHIS, the grasshopper infestation is principally one species of grasshoppers called clearwinged grasshoppers (Camnula pellucidia). There are several other species of grasshoppers common to the area. Nine additional species are common to mountain meadows.

Q. Why are there more grasshoppers this year?

A. To reach infestation levels, grasshopper populations need to have warm, dry conditions in the spring. This year, 2002, is the third year in a row where we have had above-average temperatures and below-average moisture in the spring. Warm, dry conditions allow for higher-than-normal egg hatch.

Q. Has northwestern Colorado had more grasshopper outbreaks so far this year than other areas of the state?

A. As far as I know, this is the only infestation widely publicized in Colorado. However, Moffat County is facing an outbreak of mormon crickets. Mormon crickets are also very devastating to native rangeland and have been a historic rangeland pest in Northwest Colorado.

Q. What damage have the grasshoppers caused so far?

A. The clearwinged grasshopper prefers to consume annual and perennial grasses but will consume other plants if grasses are no longer available. They have destroyed pastures, dryland hay, small grain crops and home yards and gardens. Affected landowners have also described them as alien-like in their densities, invading homes and making the ground seem as if it is moving.

Q. How much damage can they cause?

A. According to a University of Wyoming publication, one clearwinged grasshopper per yard over a season can reduce the yield of Kentucky bluegrass by 5 pounds per acre. Another study showed that one adult per square yard reduced grass yield by 1 pound per day per acre. As a comparison, a mature cow consumes about 25 to 30 pounds of forage a day. In summary, the grasshopper can completely destroy the grasses and forbs in the infestation area to where there is literally nothing left.

Q. How serious could the grasshopper infestation become? Do you expect that grasshopper populations will grow or die off over the summer?

A. It is already serious if you live, farm or ranch in the infestation area. It could become more widespread, particularly next year, if we have another warm, dry spring. The infestation is rapidly reaching a stage where all the grasshoppers become adults. As this happens, the grasshoppers will disperse over a wider area and lay eggs for subsequent hatches. Past research shows that infestations can grow to be as large as 2,000 square miles.

Q. What are people doing now to deal with grasshoppers?

A. People can 1) use a biological control agent called Nosema locustae, 2) use a common insecticide containing Carbaryl, and 3) use cultural control of keeping high-value grassy areas damp. The Nosema is only effective when the grasshoppers are in the early nymphal stages. The clearwinged grasshopper prefers dry sites, so keeping a lawn or hay meadow well watered will reduce damage. Carbaryl is commonly sold under the trade name Seven. Other insecticides may also be effective for grasshopper control.

Q. What has happened historically?

A. While no thorough investigation has occurred, a brief review of the local library's historical collection, the local museum's collection and discussions with three local longtime residents yielded no reference to a grasshopper infestation of this magnitude.

Q. Where can I find more information about grasshoppers?

A. There are two excellent sources on information available online. The Colorado State University Cooperative Extension fact sheet for homeowners is available at www.ext.colostate.edu/pubs/insect/05536.html and the most thorough information on rangeland grasshoppers is available at www.sdvc.uwyo.edu/grasshopper/rgmanage.htm.

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