Grasshoppers - They’re back in force, toting voracious appetites

HOPPER SWARM: Large numbers of grasshopper nymphs are being observed in Union and Baker counties, especially between North Powder and Baker City. Most are clearwinged grasshoppers, which can be destructive to crops and rangeland during their periodic outbreaks. Pictured here are female, left, and male, right, clearwinged grasshoppers. - Photo/Helmuth Rogg

Despite a winter longer and wetter than in recent years, the hopping insects — mostly clearwinged grasshoppers, the species predominantly observed in the infestations of 2007 — are already being noted in alarmingly high numbers in Union and Baker counties.

Helmuth Rogg, an entomologist with the Oregon Department of Agriculture, said that up to 100 grasshoppers per square yard have been observed in particular sites, mainly between Baker City and North Powder.

These densities most likely relate to egg beds, Rogg said, where last year’s adult females sought out areas of sparse ground cover and loose soil, often in great aerial swarms, to deposit their broods.

“Each female deposits up to 200 eggs in the soil,” Rogg reported in a press release. “In early spring, myriads of the clearwinged grasshopper nymphs hatch in egg beds that may contain as many as 3,000 to 100,000 eggs per square foot.”

Clearwinged grasshoppers, Camnula pellucida, are most economically destructive as nymphs. Voracious feeders, they often target small grains like barley and wheat, as well as grasses — wheatgrasses, fescues, bluegrasses and bromes. During the spring hatches, entire wheat fields are vulnerable.

Later in the year, adult grasshoppers sometimes descend on vegetable crops.

In 2007, almost 600,000 acres were affected from Elgin to Baker City, with densities of up to 50 grasshoppers per square yard.

Rogg said that outbreaks, which are usually tied to weather conditions and are unpredictable, typically last one to four years.

Last year’s grasshopper numbers, coupled with the hatch being observed so far, lead Rogg to think Northeast Oregon is on the cusp of another outbreak cycle.

The duration and nature of this past winter and early spring has delayed the grasshoppers’ emergence, Rogg said.

“If we wouldn’t have had that cold winter and late spring, we would have been up to our eyeballs in grasshoppers,” he said.

Early detection of the egg beds are crucial for mitigation efforts.

“Control options include flood irrigation of rangeland (where possible) and chemical control,” Rogg stated. “Insect growth inhibitor regulators, such as Dimilin, have a high success rate for controlling immature grasshopper populations while significantly reducing the risk to other non-target species, such as honey bees and native pollinators, and applicators.”

Dimilin is only effective, however, when applied to molting grasshoppers. The insects undergo a number of molts in their transition to adulthood, and the development of a new outer skin is essential to the process.

Dimilin suppresses the development of the new exoskeleton, preventing maturation.

“So (the grasshoppers) die in their old skin,” Rogg said.

But adult grasshoppers, fully molted, are not affected.

“Therefore, we encourage concerned landowners to check their property now for signs of young grasshoppers,” Rogg said. “In the event of an outbreak of grasshoppers, early detection increases the options available for control and their effectiveness.”

Cooperation between producers in areas affected by grasshopper swarms is essential, Rogg said, to avoid re-infestation from untreated areas.

Rogg estimated that producers in the affected area had about a two-week window in which spraying would be effective.

While Dimilin is safe around humans and bees, it shouldn’t be applied near water, as it can kill aquatic shrimp.

ODA and the USDA can only offer technical assistance to landowners for outbreaks on private property. The groups are compiling information on current grasshopper distribution and control options for local farmers and ranchers.

This information will be shared at a meeting for interested parties on Tuesday, June 24, from 3 to 5 p.m. at the Baker County Fairgrounds Event Center.

For further information about the outbreak or control options, contact Darrin Walenta, Union County Extension agent, at 963-1010; Cory Parsons, Baker County Extension agent, at 541- 403-0042; or ODA at 503-986-4662.