Plan Treatment Early: New year ominous for grasshopper infestation |

Plan Treatment Early: New year ominous for grasshopper infestation

By Rebecca Colnar for TriState Livestock News



After a summer of severe grasshopper infestation in many parts of Montana, Wyoming and the Dakotas, landowners are enjoying the winter reprieve from the insects. Although there are more than 400 species of grasshoppers, only about two dozen are capable of causing the destruction of crops and grasslands that occurred across parts of the West in 2020. Unfortunately, one bad grasshopper year is followed by another one, as they lay their eggs in the soil in the fall.

At the start of winter, the last thing any farmer or rancher wants to think about are grasshoppers, but planning ahead could help prevent another

“The attached map indicates there are areas that could have significant grasshopper populations again in 2021 in the areas that are orange and red,” noted Gary Adams, who is Montana’s State Plant Health Director for USDA’s Animal and Plant Health Inspection Service (APHIS). “We need to get suppression programs in place for next year. The sooner we can get people engaged and lined up, the better.”

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APHIS is teaming up with the Montana Department of Natural Resources and Conservation (DNRC) to see how the conservation districts across Montana can help. “I’m excited to build a relationship with the Conservation Districts to help support coordination of these Cooperative Projects,” Adams said.

He explained that APHIS relies on surveys for management decisions as it allows them to estimate how many are present; early surveys are especially good to determine treatment.

“We need to do a density survey before treatment and after. Early on we conduct a nymphal survey as we need to know early if you need help,” Adams said. “We also conduct an adult survey from late summer into early fall. Keep in mind different species hatch at different times. Mid-May is really early and some species don’t hatch until mid-June. Keep in mind that not all species hatch at the same time and even the same species hatch at different times. It’s highly variable and some people can be caught off guard later in the season.”

2020 was an ideal year for the hoppers in much of the Northern Plains. 2019 had plenty of moisture and good grass growth, followed by a mild 2020 winter which was then followed by drought. This weather was optimum for egg hatches; thus, the infestation.

To survey, Adams said to visualize a square foot and count how many grasshoppers jump out of that square foot as you approach and write down that number. Walk in a horseshoe shape, repeating this 18 times or for a total of 2 square yards. This will give you a total number of grasshoppers in 18 square feet. Divide that number by 2 to determine the average number of grasshoppers per square yard. There is also a forage calculator that can estimate how much forage may be lost at various densities for different lengths of time.

“Farmers and ranchers seeking feedback on whether or not they may need to treat for grasshoppers next year, should reach out to their State Plant Health Director for guidance. APHIS may be able to provide input based on previous surveys of the area, or may visit the site and assess various factors to determine whether action is necessary. These factors include, but are not limited to, grasshopper densities per yard, the pest species and its biological stage, treatment timing and options, and other ecological considerations. County, State, and Federal officials, tribes, and/or rancher groups may also initiate cooperative local programs and request APHIS assistance when surveys show the potential for large grasshopper populations,” according to Bill Wesela, National Policy Manager, in the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS).

This is the time to make the decision if the cost of spraying the grasshoppers is worth the forage lost. If you’re in the midst of a drought, is it even worth trying to hay?

“That’s what USDA is here for, to assist in answering those questions,” Adams said.

APHIS currently has three types of pesticides approved to treat grasshoppers as part of their program: Malathion and carbaryl are generally available and can be purchased by the general public. APHIS’ treatment of choice is diflubenzuron. However, it is a restricted-use pesticide and needs to be applied by a licensed applicator. The diflubenzuron affects the ability of the grasshopper to re-form its exoskeleton each time it molts, causing it to die. The pesticide is not hazardous to birds or mammals. Adams noted that APHIS has the best results with grasshopper control using the Reduced Agent and Area Treatments (RAATS). RAATS is basically skip swathing, with grasshopper mortality occurring in the treated swaths. Because grasshoppers are especially mobile, they generally will come into contact with a treated swath. The more predacious insects and parasitoids can still survive because of the non-treated swaths.

When a grasshopper outbreak threatens rangeland forage, landowners and managers can write and request assistance from the Rangeland Grasshopper and Mormon Cricket Suppression Program, part of the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS), to reduce rangeland grasshopper and Mormon cricket populations via suppression treatments.

APHIS treats for grasshoppers and Mormon crickets on rangelands upon written request of the landowner or manager after determining the treatment will effectively suppress populations to levels where the grasshoppers and Mormon crickets will not be able to cause significant forage loss and ecological damage.

“Last year, spraying cost less than $3 per acre, but that can vary on the bids we get from contractors. There is no guarantee on price,” Adams noted, adding that the cost is mainly determined by the contractor hired to spray, and is based on other factors such as the distance the sprayer needs to go, available airports, water access and more.

“Most importantly plan early,” Adams strongly advised. “Keep in mind we need to do a National Environmental Impact Act (NEPA) as well as site specific Environmental Assessments.

If you’re going to look for PPQ funding, requests and estimates need to be in by December 18, 2020,” said Gary.

For more information, reach out the Gary Adams, ((406) 657-6282 or or contact your local Extension Agent or the DNRC and check out Protecting U.S. Rangeland from Grasshoppers and Mormon Crickets at


Legend – Blue: 0-<3, Green: 3-<8 Orange: 8-<15 Red: 15+
Legend – Blue: 0-<3, Green: 3-<8 Orange: 8-<15 Red: 15+