Agricultural Division

News release issued June 21, 1999, effective immediately.

Now is the time to control grasshoppers

ARDMORE, OK - Grasshoppers will be a problem for many Southern Oklahoma and North Texas ranchers for the second consecutive year. That's the bad news.

The good news is that the problem does not appear to be as widespread as last year.

"There are isolated areas with very heavy infestations, while neighboring ranches in the same area may not have a problem at all," explained Jeff Ball, a soil fertility and crops specialist with the Ardmore-based Noble Foundation. "If left untreated grasshoppers can cause severe damage to pasture in a brief period of time and will be in direct competition with livestock for forage through the summer."

Dr. Tom Royer, an OSU Extension entomologist, has taken several grasshopper counts in South Central Oklahoma. He has found grasshopper populations ranging from one per square yard (nonthreatening) to 30-plus per square yard (very threatening) in bermudagrass pastures.

Due to the mild winter, egg hatching began in late February and will continue through June, Ball explained. Most grasshoppers are currently in the nymph stage, meaning they are unable to migrate and are confined to the area where they hatched, making them relatively easy to control with an insecticide. Once grasshoppers reach the adult stage, they develop the ability to migrate, making control much more difficult. If grasshoppers are not controlled on adjacent lands, adult migration may become a problem later in the summer.

"Natural enemies that usually keep populations in check are present and working," Ball said. "However, due to large numbers of eggs laid last summer and fall, 80 percent control by natural diseases may still leave 10 to 20 grasshoppers for each adult present last year.

"For optimum control with an insecticide, it is best to diagnose the problem early in the growing season. Now is the best time for treatment," Ball emphasized.

The economic threshold (the level at which plant damage saved will pay for treatment) in a pasture is 11 to 20 grasshoppers per square yard. Malathion 57% applied at a rate of 1.5 to 2 pints per acre will provide a quick kill, but offers no residual to control grasshoppers that move in from untreated areas. Sevin 80S applied at the rate of 0.67 to 1.88 pounds per acre will control grasshoppers and offer some residual control for grasshopper migration into the area after treatment.

There are no grazing restrictions on malathion or Sevin applied by air. A 14-day grazing restriction is present when Sevin is applied using a ground rig on introduced pastures. When applying insecticides, good coverage is important to achieve effective results; apply 12 to 15 gallons of water per acre to guarantee uniform coverage.

Ball explained that grasshopper populations can be suppressed by natural enemies, such as the fungus Entomophthora grylli, which often causes high mortality.

"Infected grasshoppers grasp the top of a plant with their front and middle legs while their back legs are extended. They will die in this position, and fungal spores will develop throughout their bodies. These spores become airborne and infect other grasshoppers," Ball said. "In warm, humid conditions, large numbers of grasshoppers can be controlled by this fungus.

"Be sure to scout your pastures regularly for dead grasshoppers holding on to the tops of plants to see if the fungus is present and assisting in control," he added.

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For information on the content of this news release, contact Jeff Ball at 580-223-5810

(FYI - The Noble Foundation is a privately funded, nonprofit organization headquartered in Ardmore, Oklahoma. The Foundation conducts agricultural and plant biology research; provides grants to numerous other charitable and educational organizations; and assists farmers and ranchers through educational and consultative programs.)

Web site: www.noble.org