Grasshopper numbers on the rise

Grasshopper activity is high in parts of the Oregon.

Along with a punishing heat wave, active wildfire season and a persistent drought drying up crops across the West, farmers also have to deal with growing numbers of grasshoppers and Mormon crickets.

The USDA’s “2021 Rangeland Grasshopper Hazard” map shows that parts of Eastern Oregon and Southern Idaho have high numbers of the insects. The map shows part of Oregon has densities of at least 15 insects per square yard. Eight grasshoppers per square yard are considered enough to cause economic damage on pasture and cropland, according to Helmuth Rogg, director of Plant Protection & Conservation Programs for the Oregon Department of Agriculture.

In 2020, Oregon had over 1 million acres of grasshopper infestations.

“The biggest biomass consumer in this country is not cattle, it is not bison, it is not whatever else — it’s grasshoppers,” Rogg said.

Agricultural damage from grasshoppers can be catastrophic. Grasshoppers can eat 30 to 100 milligrams of dry plant material each day, and six to seven grasshoppers per square yard will eat as much as one cow.

According to the USDA, the 17 western states impacted annually by the insects have an average of $400 million in forage losses and 20% cropland losses.

This spring, officials worked with private landowners in Klamath County and Harney County, advising the community on spraying just as grasshopper eggs hatched. For the most part, it worked in that area.

Agriculture officials have also seen a spread in other areas such as Baker County in Oregon and Walla Walla County in Washington.

This year, the Animal and Plant Health Inspection Service contracted treatment for 19,000 acres and protected approximately 39,000 acres through cooperative treatment projects, said Clint Burfitt, state plant health director for APHIS in Oregon.

Rogg said the state spends between $2 and $4 to spray an acre.

In spring, grasshoppers hatch from their egg and gorge on food until their bodies are big enough to grow genitalia and wings — cementing their adulthood. That is their current stage in Oregon, meaning Dimilin, an insecticide that interferes with molting in immature stages of insects, is now ineffective.

“At this point, it’s too late to do something about it because the damage is already done,” said Rogg.

However, land managers can contact local area applications to arrange other treatments independently; APHIS will provide technical assistance for treatments.

Parts of Oregon and Idaho are also battling a Mormon cricket infestation.

This spring, some Idaho residents experienced an infestation of Mormon crickets and shield-backed katydids as millions made their way through the Owyhee rangeland, according to KIVI-TV.

However, some environmentalists worry about the impacts pesticides meant to manage the insects will have.

“These are grasslands, sometimes with hundreds of different native pollinator species found in them...,” said Aimee Code, pesticide program director with the Xerces Society for Invertebrate Conservation, a conservation group focused on insects.

Sharalyn Peterson, a healthy wildlife and water program manager at Northwest Center for Alternatives to Pesticides, suggests insecticides that are less toxic such as BotaniGard ES and Safer BioNeem, which stunt population growth. Organic biocontrols such as Nosema locustae offer long-term grasshopper protection, she said.

Rogg said Dimilin is relatively safe to use in pasture settings as it should not harm other insects such as butterflies, which go through a pupa stage before becoming an adult.

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