Heavy grasshopper infestations warrant treatment

Writer: Kay Ledbetter, 806-677-5608, skledbetter@ag.tamu.edu
Contact: Dr. Ed Bynum, 806-677-5600, ebynum@ag.tamu.edu

AMARILLO – Farmers and homeowners alike are battling against a heavy infestation of grasshoppers in the High Plains, and while tiny now, without treatment they could double in size, numbers and amount of damage.

“Looks like it could be a bad year for grasshoppers,” said Dr. Ed Bynum, Texas A&M AgriLife Extension Service entomologist in Amarillo. “If you have been out any at all you already know that they are everywhere.”

Bynum said there’s a wide assortment of grasshopper species present. The egg hatch typically ends by late June, but the nymphs will be molting four to five more times and will become adults over the next 40 to 60 days.

And that’s when the real damage will begin, he said.

“Right now the pastures, Conservation Reserve Program fields, grasses and ditches still have a lot of green plants for the grasshoppers to feed on, which keeps them out of the field crops in large numbers,” he said.

With warm, humid weather, grasshoppers can become infected and die from a naturally occurring entomopathogenic fungus, Bynum said. Infected grasshoppers move to the top of a plant and die in a characteristic pose, with the front and middle legs grasping the object and the hind legs extended out.

He warned, however, it is more likely they won’t be affected by this fungus in the High Plains and will continue to grow and become more difficult to control.

AgriLife Extension publications recommend control measures begin while grasshoppers are still young nymphs and to treat along the hatching sites – roadsides, fencerows, etc.

Treating now can mean fewer acres need to be treated, requiring less insecticide, and excessive crop damage might be prevented, Bynum said. Also, the nymphal stage grasshoppers are not able to fly and are more susceptible to insecticides than are the larger nymphs and adults.

“But, if you are the only one treating, then your acreage may be re-infested and overrun when grasshoppers can fly and migrate,” he said. “The ideal situation would be to coordinate an area-wide spray program among producers within and across counties.”

To control the grasshoppers, Bynum said insecticide sprays and baits are the primary options. Baits are effective, but limited to those grasshoppers it attracts. Insecticide sprays can be used for larger acreage and are more economical. Canola oil added to the insecticide spray has been shown to improve control by making the treated plants more attractive to the grasshoppers.

He said there are numerous organophosphate, pyrethroid and other classes of insecticides labeled for grasshopper control in field crops. Primarily the pyrethroids will be labeled for urban/homeowner use. Sevin products with carbaryl also are labeled for use by homeowners and in urban landscapes.

Each product is labeled for specific crops or non-cropland usage and should be consulted before use, Bynum said.

Another insecticide labeled for select crops and non-cropland areas is Dimilin 2L, a bio-insecticide. This product is an insect growth regulator that interferes with grasshopper nymphs ability to molt to the next life stage, he said.

“Since adults do not molt, this product is only effective against the small to medium sized immature grasshoppers,” Bynum said. “But it does have a long residual activity.”

Two other products with a new chemistry insecticide are Besiege and Prevathon. These products contain the insecticide chlorantraniliprole, which provides good control of grasshoppers.

Prevathon only has this insecticide as its active ingredient, but Besiege is a chemical mixture of chlorantraniliprole with a pyrethroid insecticide. Both products are labeled for use in several crops and for range, pasture, and forage and silage production of grass, Bynum said.

“But, neither of these products are labeled for use in non-cropland areas, so that means that homeowners do not have them as an option,” he said.

Bynum warned all chemicals have restrictions, so it is important to read the labels before use.