Grasshopper numbers on the rise

Grasshopper outbreaks often follow or coincide with drought years as low rainfall and warm spring weather create ideal conditions for egg hatches and the survival of small nymphs, according to the Oregon Department of Agriculture.

SALEM — Surveys are underway on rangeland across Eastern Oregon for grasshoppers and Mormon crickets after last summer’s outbreak, which was one of the worst in 50 years.

Grasshopper outbreaks often follow or coincide with drought years as low rainfall and warm spring weather create ideal conditions for egg hatches and the survival of small nymphs, according to the Oregon Department of Agriculture.

Last summer was a prime example, with ODA reporting a record 10 million acres sustained economically damaging levels of infestation on farms and ranches in 18 counties. About 40% of the damage was in Harney and Malheur counties in Southeastern Oregon.

In response, state lawmakers approved a one-time $5 million allocation for grasshopper and Mormon cricket suppression, including $803,207 for expanded surveys on public and private land and $4.19 million for treatments under a cost-sharing program administered by ODA.

Todd Adams, survey coordinator for ODA’s Eastern Oregon Field Office in Hermiston, said the agency is starting to receive reports of grasshoppers hatching, including at higher elevations near Jordan Valley along the Oregon-Idaho border.

“We are expecting to see a similar type of year (to 2021),” Adams said.

Grasshoppers are voracious eaters, and having eight or more per square yard is considered enough to cause economic damage on rangeland.

According to ODA, 15 to 20 grasshoppers per square yard spread out over a 40-acre field of alfalfa will eat 1 ton of hay per day, and seven grasshoppers per square yard over 10 acres can eat the equivalent of one cow feeding throughout the season.

“In Jordan Valley, the only thing left was sagebrush,” Adams said of last year’s outbreak.

While Oregon has 100 species of native grasshoppers, only about a dozen of them have the potential to create pest outbreaks, Adams said. He highlighted a few species, including Camnula pellicuda, or the clearwinged grasshopper, and Aulocara elliotti, or the big-headed grasshopper.

Oregon also has several populations of Mormon crickets: near Arlington along the Columbia River, Jordan Valley, Enterprise in Wallowa County and a newer population near McDermitt along the Oregon-Nevada border.

Mormon crickets can cause similar damage to crops and forage.

They are not crickets, but flightless katydids that move together in swarms. The population in Arlington has been at outbreak level since 2017.

To control grasshoppers and Mormon crickets, Adams said diflubenzuron, a growth-inhibiting pesticide, is used. It affects the insects’ molting when they shed their exoskeleton.

Diflubenzuron does not kill adult insects and must be sprayed when they are still in their nymphal stages.

Adams said it is critical for ranchers to look for signs of grasshopper activity so ODA can survey their pastures and prescribe a treatment plan.

“They’re hatching throughout most of the state now,” he said.

Treatments on public land will be done by the USDA’s Animal and Plant Health Inspection Service in coordination with ODA. Private landowners and land managers can apply to be reimbursed for treatments through the state’s cost-share program. Applicants must first receive a treatment plan from ODA to qualify.

For more information or to request a survey, visit www.oregon.gov/oda, or call {span}503-949-2993.{/span}

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