A population explosion of grasshoppers in the Texas High Plains has AgriLife Extension pest management officials warning farmers to spray now to help lower the number of young nymphs in the field because they are more susceptible to insecticides than they are at later growth stages.
Reports from across the High Plains drifting in this month indicate "an exceptional swarm" of grasshoppers across large areas of the Panhandle. Entomologists say grasshopper nymphs typically hatch in the early, hot summer months, specifically in June and July, often following a wet spring. The nymphs then molt four or five times before becoming adults.
While grasshopper swarms are not unusual across the Southwest, they are problematic some years, only to skip several years until the right climate conditions encourage another spike in numbers.
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Charles Brown, United States Department of Agriculture's Animal and Plant Health Inspection Service's (USDA-APHIS) policy manager for the Rangeland Grasshopper and Mormon Cricket Suppression Program, says in excessive outbreaks, grasshoppers can pose a serious risk to rangeland grasses and field crops.
"We had a serious outbreak in the 1980s and have seen some serious but smaller outbreaks a few years back. But we're not expecting a massive outbreak this year though we will continue surveying problem areas," Brown said.
At greatest risk are rangeland grasses, but a large enough outbreak can cause swarms of grasshoppers to seek alternative food sources.
Ed Bynum, an entomologist for Texas A&M AgriLife Extension Service, says grasshoppers generally lay eggs in late spring. April and early May showers may be instrumental in elevated numbers now that hot weather is settling in across the Panhandle.
Don’t delay applications
He recommends vegetable farmers and home gardeners should spray sooner than later to avoid applying chemicals later in the season to target other plants such as ornamental grasses, some herbs as well as vegetables. He says those who are seeing large numbers of grasshoppers or nymphs should scout nearby ditches and weedy areas where nymphs can have high populations following a cool spring. Stopping them at nymph stage is much easier than waiting until adult grasshoppers attack plants.
"Small nymphs tend to stay in the grassy areas, and treating them early is a bonus because they are not yet spread out and rooted in field crops. So, if you can spray when they’re young, you have better control." Bynum added.
Panhandle Greenhouses Manager James Cathey in Amarillo says reports from across the High Plains area indicate large swarms of grasshoppers and warns that the problem could intensify as the pests reach advanced growth stages.
"Just about everyone is reporting grasshoppers, and in some areas thousands being reported," he said.
Plant and soil specialists at Texas Tech University's Department of Plant and Soil Science Resources say grasshoppers like to bury their eggs in soil. After hatching, they move into nearby weeds and grasses until they begin to mature. In sufficient numbers they can devour rangeland grasses and can cause serious damage to nurseries and vegetable farms.
For vegetable farmers, certain plants such as lettuce, carrots, beans, sweet corn, and onions are favored. Squash, peas, and tomatoes (leaves, not fruit) are among the plants grasshoppers tend to avoid. Scouting crops and watching for leaf damage can help manage grasshoppers, but timing insecticide applications is critical on vegetable crops.
Other areas being hit
The Texas High Plains is not the only area seeing elevated numbers of grasshoppers this year. Sporadic outbreaks are being reported in New Mexico and Colorado, also spawned by early spring rains and warmer summer temperatures.
W.S. Cranshaw, Extension entomologist at Colorado State University, warns that grasshoppers are difficult to control because of their mobility.
He says baits containing carbaryl (Sevin) can be broadcast. Bait formulations are made by mixing the insecticide with bran or some other carrier to target grasshoppers that feed on the bait. These treatments limit application effects on other insects present in the treated area. However, availability of Sevin baits is frequently limited, or prohibitively priced for use on large areas, and baits must be reapplied after rain.
Chemical alternatives include acephate and permethrin, but restrictions apply. Acephate can be used on non-edible crops and permethrin is widely available for gardens and most vegetable crops. Cranshaw advises farmers and homeowners to consult with county agents before applying chemical treatments.