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A contractor's plane applies diflubenzuron in the Kirby Creek area.

A contractor's plane applies diflubenzuron in the Kirby Creek area.

grasshopper on leaf.
It’s possible this resting grasshopper was picked off the leaf, soon after the photo was taken, by a pair of Mountain Bluebirds feeding young nearby.
Boone Herring, APHIS PPQ technician, inspects the contents of his net during grasshopper surveys.
Boone Herring, APHIS PPQ technician, inspects the contents of his net during grasshopper surveys.

Multi-Agency Partnership Battles Grasshoppers

By C.J. Grimes, BLM Invasive Species Coordinator, Worland Field Office

For people who depend on crops or rangeland for their livelihood, talk of a grasshopper outbreak can be stressful, or even scary. When hopper numbers exceed 15 per square yard, it is estimated that they can consume 30 percent of available forage. Predictions of high grasshopper numbers, based on USDA APHIS PPQ (Animal and Plant Health Inspection Service, Plant Protection and Quarantine) surveys in 2009, have proven accurate in the Bighorn Basin. The highest hopper counts are being reported in the southern and eastern portions of the basin, up to approximately 6,000 feet in elevation.

However, not all grasshopper species are considered pests. Some species eat weeds almost exclusively, and they are in turn eaten by a variety of wildlife species from songbirds and sage-grouse to small mammals and even trout. Problems occur when a local or regional grasshopper population increases to such a high level that it causes economic damage to crops and rangeland. For this reason, a multi-agency partnership has been working together to reduce the numbers of grasshoppers to a level that will not cause significant economic damage.

In the fall of 2009, APHIS staff created potential hazard maps for 2010, based on where they had recorded high survey counts earlier that summer. The counties hosted public meetings for landowners, farmers and ranchers to discuss the possibility of an outbreak, provide treatment information and encourage participation in treatment programs. This was not an easy task, considering the mix of private, state and federal land ownership in the Bighorn Basin, but it was necessary to establish an effective control program. “We really needed landowners to be on board early for this program to work,” said Marvin Andreen, Hot Springs County Weed and Pest Supervisor.

As summer approached and landowners signed-up for the cost-share spraying program, APHIS personnel worked long hours finalizing spray block contracts to be prepared for the peak of the grasshopper hatch in June. According to Boone Herring, an APHIS PPQ technician, the most economical way to control an outbreak of hoppers is to apply a chemical called diflubenzuron using a RAAT (reduced agent area treatment) strategy. “Diflubenzuron doesn’t affect non-target species like bees and butterflies,” Herring explained, “and the method we use doesn’t eradicate all the grasshoppers in an area. Some are left available as prey for wildlife.” Given that sage-grouse populations occur throughout the basin, this is a critical consideration.

While APHIS organized several large, contiguous spray blocks across the state, numerous smaller areas where grasshoppers posed potential harm to crops and forage also needed to be addressed by county weed and pest supervisors. BLM Wyoming was able to secure funding to assist Bighorn Basin counties in their efforts. “Grasshoppers have hit Washakie County hard this year, but we are working even harder to control the damage” said Jarrod Glanz, Washakie County Weed and Pest Supervisor. “You can do your part by using hoppers for bait when you go fishing.”

Basin-wide, approximately 330,000 acres have been protected by the control program, and some treatments are ongoing. The cost for these treatments, shared by the BLM, APHIS, State of Wyoming and many private landowners, has reached approximately $500,000.

Will next year also bring high hopper counts? It is difficult to say, since natural boom-and-bust cycles have occurred for centuries. Glanz says he’ll be happy if populations decrease next year. “I can’t wait to get back to killing weeds.”

For more information, please contact C.J. Grimes at 307-347-5100 or visit the BLM’s grasshopper webpage at: www.blm.gov/wy/st/en/programs/weeds_pests/grasshopper.html.

Last updated: 08-12-2010