Extension offers solutions for grasshopper issues

With the hot weather here, it might be too late to effectively get rid of the pesky grasshoppers, but Wendy Carr of the Sanders County Extension Office doesn't believe it is hopeless yet.

"After they have grown to the adult stage one can use Lambda-cyhalothrin, which is a synthetic pyrethroid, often times purchased as the brand names Warrior, Round House, or Silencer," said Carr. She said that it's a broad spectrum insecticide, but if the product carries Lambda-cyhalothrin, a private applicator's license is required for use. Other recommendations at the adult stage include carbaryl, cyfluthrin, 7-5 bait, and malathion.

Spring is the best time to manage grasshoppers when they are nymphs and haven't had the chance to eat too much, according to Marni Rolston, an arthropod diagnostician with Montana State University at Bozeman. Rolston said that the later the grasshoppers get treated the bigger and more resilient they get and the harder it is to get rid of them. In addition, when they get larger they become more destructive.

Grasshoppers, depending on the species, will eat everything in sight, said Gary Adams, the U.S. Department of Agriculture State Plant Health director at MSU. He said that some species feed primarily on grasses, some primarily on broadleaf plants, but he added that some will consume both and a few select only weeds, like the snakeweed grasshopper. "Sometimes it seems they'll eat everything in sight on large infestation years. I've even had people report them eating clothes they've hung on their clothes line," said Carr, the agriculture, horticulture, and natural resources specialist in Thompson Falls.

Carr said that it's a little on the late side for spraying the most helpful stuff, Dimilin, but it might help for next year. "If adults are already present they could add a second insecticide for adults," she said, adding that it depends on each area's hatches if it is too late for Dimilin or not. "It is best to use this before they fly, so people should do a survey to see if their hatches are flying or not and this can help steer them to what insecticide to use," she said. Carr also said not to rule out some of the more organic methods, such as adding scents to a yard or garden, which makes the areas less attractive to grasshoppers. "Although you will have to experiment with what scents deter the specific grasshoppers you have, some suggested scents and plants that grasshoppers stay away from include garlic, rosemary, peppermint oil, thyme, basil, cayenne pepper, onion, clove oil, cilantro, squash, peas, and tomato leaves, although some species may still eat these," said Carr.

"It will be more difficult to treat them in July and August because they're more mobile and treatments aren't as effective," said Rolston of the Shutter Lab, located at MSU. Lab staff members there help identify plant diseases, insects and herbicide and insecticide injury on horticultural and agricultural plants free for the residents of Montana. Rolston noted that adult grasshoppers are the most damaging stage because they're bigger, eat more, and can quickly fly from one area to another. "Nymphs can't fly, but if they hatch in areas without suitable or sufficient food, they can move, at times in swarms, by crawling and hopping. Grasshopper control is most effective for nymphs since they aren't as mobile and are more susceptible to insecticides," she said.

At the point where grasshoppers are half grown, one of the most effective insecticides is diflubenzuron, according to Adams, who said that the rangeland treatment program prefers to use "insect growth regulators," such as diflubenzuron and treat every other swath, but he added that it is a restricted use pesticide and not available to everyone. The extension office at Thompson Falls offers a test to become a private applicator. Carr said that diflubenzuron, often purchased under the brand name "Dimilin," works by disrupting the formation and deposition of chitin in the exoskeleton, which interrupts the immature grasshopper's ability to molt. "Effects of treatment will normally appear within three to seven days, as the grasshopper nymphs fail to molt and then die," she said. "Other pesticides may be effective on adult grasshoppers, but by then they are highly mobile, mating and laying eggs," said Adams.

"I know the weed shop has been recommending Eco-Bran for a more environmentally friendly option for around gardens. She said that according to the Eco-Bran website, it kills grasshoppers fast and is for growers that require immediate control and is environmentally sensitive. In addition, EcoBran only impacts insects with chewing mouthparts, such as grasshoppers, crickets and cutworms.She also said that studies from the U.S. Department of Agriculture show that EcoBran does not impact birds and it has little or no effect on beneficial insects.

Rolston said that Montana has about 70 different species of grasshoppers, but of these only about two dozen are considered pests. Carr said the primary species of grasshoppers in Sanders County are Camnula pellucida, also known as the clear-winged grasshopper, the Melanoplus sanguinipes, the lesser migratory grasshopper, and the Melanoplus bivitattus, the two-striped grasshopper, which can all be a significant pest species. "Some of the species that cause significant crop damage are the clear-winged, the migratory, the two-striped, the packard, the differential, and the red legged grasshoppers," said Carr.

Rolston said that for most species, the females lay about 100 eggs in hard packed soil in the summer and fall. "The eggs are deposited within a frothy liquid that hardens and acts as a protective barrier. Grasshopper nymphs hatch out of their eggs in the spring, molt five times and reach the adult stage within about five or six weeks," said Rolston, who added that adults live for two to three months, depending on the weather. "Grasshoppers are ectotherms, like all insects, which means they depend on external temperatures to stay warm and grow. The warmer their natural environment is, the faster they will grow and develop."

The arthropod specialist also stated that grasshoppers can do a lot of damage in Montana, particularly on rangeland, crops, gardens and landscaping. "In a normal year when there's plenty of moisture, grasshoppers remove approximately 20% of rangeland vegetation and feed sporadically on crops, but their damage isn't very destructive because plants can compensate for this feeding injury by regrowing.

However, grasshopper populations are cyclical, and when outbreaks occur (every 8 to 10 years, often during droughts), rangeland infestations result in significant economic losses for producers," said Rolston, who suggested that late in the summer it might be helpful to mow a wide strip between grassy or weedy fields and a garden to deter hoppers from migrating into a garden. "Grasshoppers can be difficult to manage. If they were a problem last year, they will probably be again this year," said Rolston. Carr said that it's important that neighbors also treat for grasshoppers, otherwise, they will just move in on neighboring properties even if you have treated. Rolston said there are a lot of natural enemies of grasshoppers - birds, predatory insects and spiders, blister beetle larvae, which feed on grasshopper eggs, parasites and pathogens.