Grasshoppers and Mormon crickets are among the most economically important pests in the world.
David Branson, ARS entomologist, researches both grasshoppers and Mormon crickets, trying to find solutions to control them and to give producers tools to manage the insects.
Mormon crickets are a major problem in the southwestern part of the country, but they have also been spotted in Wyoming and other Western states, Branson said.
“Mormon crickets are a big problem especially in the southwest,” Branson said. “Millions of crickets sort of march along and can ruin rangeland and cropland.”
Branson is currently studying grasshopper/Mormon cricket interactions in Wyoming.
The problem with spraying grasshoppers on rangeland is that the forage on rangelands is not as valuable as cropland.
“Your cost is high relative to your return,” he said.
In crops, it is a different approach because crops are valuable.
The main insecticide used is Sevin XLR, a product in the carbamate group. It must be ingested by the grasshoppers, and in a large outbreak, usually has to be sprayed several times to gain a good result.
Sevin dust works on Mormon crickets, as well.
ARS scientists are also researching a fungus bait formulation for grasshopper and Mormon cricket control.
Producer should look for grasshopper nymphs that are active in field ditches, and crop edges.
Treatments made during grasshopper outbreaks, when densities can be 60 or more per square meter, still leave a number of grasshoppers that may be higher than the number of grasshoppers found in a normal year.
Grasshopper nymphs migrate into cropland from weedy areas and ditches. Nymphs look like adult grasshoppers but are smaller and have wing pads instead of wings.
While most grasshopper species overwinter in the egg stage in pods just under the soil surface, a few species spend the winter in one of the older nymph stages, molting into adulthood in early spring.
Grasshopper nymphs typically go through five molts before the final sixth molt into adulthood.
Branson is working on other controls for grasshoppers, including biological controls.
Habitat management techniques are ways of manipulating the quality of habitat available for grasshoppers and/or their predators, thus reducing grasshopper outbreaks.
“Burning grasslands or using livestock grazing can help significantly, and ARS has studies looking into these biological controls,” Branson said.
A promising ARS study found that during an outbreak period both grasshopper densities and forage consumption were five to nine times lower in twice-over-rotational grazing pastures than in season-long grazing pastures.