Threat to crops? Watch is on for grasshoppers

Experts are keeping a watchful eye on eastern Washington rangeland this spring, looking out for what could be a big year for grasshoppers.

“This could be a big year out around the Hooper country and also the breaks of the Snake River,” said Steven Van Vleet, WSU extension agent for Whitman County.

A large outbreak of grasshoppers could devour and damage grazing grasses and crops.

The university Friday issued a news release that warned the mild, dry spring created conditions for a massive grasshopper outbreak this summer.

Larry Skillestad, a technician for the USDA’s Plant Health Inspection Service, said his agency has seen a steady increase in eastern Washington grasshopper populations over the past three years and agreed this spring could bring on an outbreak.

“We really anticipate that we’re going to see a lot of grasshoppers yet this season,” said Skillestad, “Whether they mature to adulthood or not depends on a lot of different factors.”

Skillestad said cold and rain in the next few weeks could prevent grasshopper larva from reaching maturity.

USDA agents are currently scouring the state to survey grasshopper nymph populations. By counting the amount of young grasshoppers in a square yard, they can predict the potential summertime population.

“Last week we were out on our hands and knees to find hoppers,” said Skillestad.

Adult grasshoppers on the Palouse begin to show up in mid-to-late June when temperatures heat up. They then begin to munch on the grasses and forbs in ranglelands like those along the Cow Creek drainage and along the Snake River breaks.

Last August, USDA researchers counted 15 to 20 adult grasshoppers per square yard in rangelands in western Whitman County and along the Snake River breaks.

Skillestad noted those adult grasshoppers could have mated and laid as many as 5,000 eggs.

While that may seem like a lot, very few of those eggs will reach maturity. Fungus, parasites, predators and weather wipe out most of the grasshopper larva before they hatch.

Skillestad said weeks still remain where moisture can prevent nymphs from maturing. When they get too cold or wet, they lack the energy even to eat, he said.

Populations of up to 15 grasshoppers per square yard can live off the same grasses that will support a cow and a calf.

When counts top that, they begin to pose problems to ranchers by devouring most of the grass meant to be grazed by cattle, said Steve Miller with the USDA.

Once warmer summertime temperatures begin to dry out rangeland grasses, the grasshoppers have to look for food – often in neighboring cropland.

Van Vleet said grasshoppers typically turn to garbanzo fields first after their grassland supplies run out. Skillestad said different species enjoy different field crops. Danger to field crops depends on how many grasshoppers mature of specific species.

Several methods exist to control larva populations. Those range from traditional pesticides to more modern chemicals.

George Bruno, also with the USDA, said he recently helped test a chemical in Nebraska that hardens the exoskeleton while the grasshopper nymphs grow, preventing them from molting. Once the larva grow too large for their outer shell, they explode into pieces.

Miller said for now the key is for ranchers in grasshopper-rich areas to be vigilant. He urged them to inspect for the pests as they patrol their range areas.