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Grasshoppers are among the most conspicuous insects in Utah, and are viewed by many as also among the most injurious to our crops and rangelands. In any given year, thousands of acres may be sprayed throughout the state to reduce potential damage.
About 400 different grasshopper species are native to North America, and most are well-adapted to forage and grasslands in Utah.
Area-wide treatments are generally more effective than spot treatments because grasshoppers are highly mobile insects.
CHEMICAL CONTROL:
Killing and managing grasshoppers, unfortunately,are often not synonymous. Grasshoppers are readily killed readily by insecticides but often large acreages need to be treated. Given the great mobility of grasshoppers, area-wide treatments may only reduce populations that year. Ranchers are encouraged to scout for grasshopper "hot spots," that is, local areas in which grasshoppers concentrate egg-laying and outbreaks first occur. All too often, huge populations of grasshoppers grow and spread before control measures are taken, thus greatly increasing both the costs and difficulties of control attempts. USDA-APHIS is responsible for control programs against grasshoppers on public lands. When grasshoppers occur at high numbers (>8/yd2 over at least 10,000 contiguous acres of privately owned rangelands), the owners may join together to receive state and federal aid in planning and conducting a large-scale Cooperative Rangeland Grasshopper Management Program.
The condition and forage value of the rangelands affected must be weighed against the potential for damage from grasshoppers to determine whether control costs are justified. A grower may be able to prevent severe crop infestation late in the season by regularly checking grasshopper breeding grounds earlier in the season, and treating with insecticide in years when nymphs are extremely numerous.
Grasshopper control products are available in spray,dust, or bait formulations. Dusts and baits are relatively expensive products, but can be applied to specific areas without sophisticated equipment. Dusts do not readily adhere to foliage and must be reapplied frequently. Baits must be consumed and are most effective when host plants are scarce, small, or have dried up. Use of carbaryl bait (wheat bran laced with carbaryl) is a particularly desirable alternative to spraying for grasshoppers in pastures, fence rows,wasteland, and along roadsides. Spread evenly through the habitat, the bait selectively kills only grasshoppers and other insects that consume it in while foraging. Nymphs are most likely to injure crops while actively foraging for dry plant material on the ground,and therefore their populations are very effectively reduced in number by baits.
Malathion and carbaryl are relatively non-toxic to humans, and may be sprayed to kill grasshoppers along roadsides and fence rows by following label directions. Other products registered for grasshopper control in Utah include acephate, beta-cyfluthrin, bifenthrin, chlorpyrifos, dimethoate, and lambda-cyhalothrin. These sprays will be most effective when used against nymphs rather than against adults.
BIOLOGICAL CONTROL:
Several reduced risk products for grasshopper controlare also available in Utah. Nosema locustae (Canning),sold as Nolo Bait, is a microsporidian protozoa that infects grasshoppers through baiting. Under ideal conditions coinciding with peak nymphal emergence,N. locustae will kill 50-70% of the population and 35-50% of the surviving grasshoppers will be infected. Infected grasshoppers are weakened, feed less, and produce fewer eggs. Optimal suppression with Nosema requires a few steps:
1) species identification 2) treating young nymphs 3) treating on sunny mornings 4) treating populations 5) treating large acreages
The disadvantages of Nosema are:
1) peak mortality occurs 4 to 6 weeks after application 2) it is most effective when applied to large areas with relatively sparsevegetation 3) conventional insecticides are still required to supplement area-wide management
Another biological control agent labeled for control of grasshoppers is a fungal pathogen, Beauveria bassiana. Many other natural occurring enemies for grasshoppers in Utah do exist. Likely, a combination of predators, parasites and pathogens contribute to grasshopper control every year.
