Wyoming, Montana: Bumper crop of grasshoppers tormenting farmers, ranchers

Rebecca Colnar
for Tri-State Livestock News

They eat fence posts. They eat leather bridles. They consume their body weight daily. A new sci-fi horror film? No, although many farmers, ranchers and gardeners in parts of Montana, Wyoming and surrounding states can confirm the source of the destruction: grasshoppers.

It has been reported that 20 grasshoppers per square yard will eat or destroy as much forage as a 1,000-pound steer will consume.

Many counties in Montana and Wyoming have been inundated by grasshoppers of all sizes; some started as early as May, others appeared recently. Some areas may have lighter infestations, in other locations a person can’t walk across the lawn without a barrage of hard bodies smacking into them.

“There doesn’t seem to be anything they don’t like to eat,” said Callie Cooley, Montana State University extension agent based out of Yellowstone County, that has had their share of grasshopper infestations. “If people didn’t spray early, they have experienced significant crop loss; but even if you do spray in an attempt to manage them, many people saw very little effect from spraying. Some people have sprayed multiple times. We are harvesting wheat and barley right now in Yellowstone County and trying to get that crop out of the field before the grasshoppers get it. They also have had a real impact on rangeland. Once they get to the adult stage, they are difficult to manage.”

Cooley noted that some of the best options are early spraying with registered-use pesticides. Some of the control products are hard to come by now since private, commercial and aerial sprayers have all been very busy this year.

The intensity of grasshoppers varies county to county and even area to area. The degree of infestation has moved across Montana, some seeing heavy pressure early in the summer, some having more pressure recently from the adult populations.

According to University of Wyoming’s entomologist Scott Shell, areas in southeast Montana and northeast Wyoming have been especially hard hit. “Platte and Fremont counties have been hard hit along with Natrona and Hot Springs County,” Shell said. “Persistency is key; you just have to be patient as we begin to approach some cooler weather.”

“If the grasshoppers lay eggs in the ground and if they hatch you have an outbreak,” Shell said. “A long time ago as a student, my professor told me that every year grasshopper eggs go in the ground, if they hatch, you have an outbreak. If you have a year when conditions are good for survival, or if the previous year was high in numbers, the grasshoppers produce a lot of eggs. Weather can have a major impact on egg production. Even in drought grasshoppers can stay in good shape on pasture land that larger wildlife or cows would starve to death on. The grasshoppers eat grass beneath what a cow can get into. High humidity will kill grasshoppers. Hard driving rain and prolonged cold will generally kill them since, being cold blooded, they won’t be able to eat and will starve.”

Most of the time grasshoppers will subside on their own due to weather, although if you have a couple of good grasshopper years, look for a population buildup and a lot of eggs being laid. There are 120 species of grasshoppers with the majority hatching in spring and laying eggs in the summer. Once the eggs are in the ground, unless they are killed for some reason such as crop tillage, they hatch. With winter wheat, grasshoppers move into wheat seedlings. Ideally the time to deal with them is in early spring.


Crop damage is often first observed along the field margin as grasshoppers migrate from surrounding grassy areas. In some cases, they may cause yield damage more directly, by clipping off wheat heads or by preferentially feeding on developing pulse crop flowers.

Most methods for managing grasshoppers rely on insecticide applications based on scouting, and thresholds depend on the crop being protected. Biological and cultural control options are generally not highly effective.

“It’s imperative to scout the field and get them treated before they reach adulthood and lay eggs,” Shell said. “Forage is lost to adults, and once their eggs are in the ground, you deal with their offspring the next year.”

Figure out where the grasshoppers are, get together with your neighbors and spray. The economy of scale on spraying for hoppers is huge. USDA Animal Plant Health Inspection Service provides technical assistance free of charge. They help with scouting and let a producer know if the density is worth spraying. They will cost share the spraying on any federal land.

“A lot of time ranchers don’t really notice them much until they are adults and flying across the hood of their trucks,” Shell said. “People are pretty much reactive when it comes to treating grasshoppers because they occur infrequently enough.”

According to literature from Montana State University, most grasshoppers overwinter as eggs enclosed in a pod laid in the top few inches of undisturbed soil. These elongate pods may contain from eight to 30 eggs, and females may produce up to 100 eggs during the season. Grasshoppers hatch earlier in a warm spring, with the two-striped grasshopper being the earliest. It hatches from mid to late May, while the other species will hatch from one to three weeks later. Hatching will continue well into June. Nymphs start feeding immediately and have the same host range as adults. Nymphs will mature into winged adults in five to six weeks. Adults can start dispersing from nymphal feeding areas by late June and early July. Few nymphs will be present by August. Grasshoppers feed during the day and rest during the afternoon and night on vegetation.

Gary Heibertshausen, a sheep rancher from Alzada in the far southeastern corner of Montana, said, “Our grasshoppers showed up the first part of June, coming in on eastern winds. First, we noticed a few, then as they hatched, they kept getting thicker and thicker. That’s the same time Mother Nature turned off the moisture valve. Our hay was lean anyway and the grasshoppers were taking the light green growth full of protein. By late June, our alfalfa was only stems and same with native grass. In the sheep business, this is the time when lambs are getting old enough so the ewes are kicking them off. The lambs live on the fine, green grass because it’s easy on their mouths, which makes them gain well. Since the ‘hoppers ate all of that, I think we’re going to see a negative effect on the weights this fall.”

The rancher said the only way he sees them stopping is “if Mother Nature throws us a curve ball and brings a lot of moisture; otherwise their eggs will winter over. The only thing we can do is get together with other landowners and work with the Bureau of Land Management and other agencies to do a mass spraying. I know some people who have sprayed and it slowed the grasshoppers down a bit, but they still weren’t able to save their crops.”

He related the tale of his neighbor who had a brand-new bridle and bit in his tack room; the insects ate all of the leather off the bit. They’re eating any wood that’s soft.

“The front of my truck is solid grasshoppers from driving,” he said. “They keep moving in; it seems we have hundreds of thousands of small ones with another hatch. If you have a piece of tin lying on the ground and turn it over, it’s crawling with them.”

Heibertshausen, who serves as District 5 director for the Montana Farm Bureau, said that not only have they eaten all the forage, they’re hazardous to man and beast. “If you’re going 20 mph on your ATV and those big, mature grasshoppers hit you, it hurts. It’s making horses and cows flightier. The lambs are having a hard time being content, and our dogs are having a heck of a time because they keep jumping on them.

“Even though we’ve gotten some rain, it doesn’t seem to be stopping them. They just keep munching up the green grass,” Heibertshausen said. “Of course, it’s just another factor to deal with along with COVID-19 and low markets. This is one of those years you can’t wait to turn the calendar. You just hope 2021 is a lot better.”

Additional information can be found on the USDA ARS Sidney grasshopper website at The High Plains IPM Guide website,, provides detailed information on sampling, thresholds and management. County extension agents have information, as well. ❖