Two fungi may represent a natural solution to the problem of millions of grasshoppers leaping across parts of the western United States each summer. Both are like a fatal case of athlete's foot to insects, producing infectious spores that hoppers can pick up on their feet.
Stefan T. Jaronski, an insect pathologist with the Agricultural Research Service, is studying these fungi and other microbes in hopes of keeping soaring hopper populations in check. He works at the agency's Northern Plains Agricultural Research Laboratory in Sidney, Mont.
During outbreaks, which are often driven by droughts, grasshoppers can gobble up valuable crops, forage and ornamental plants, costing millions of dollars in damage.
One fungus, Beauveria bassiana, is already registered in the United States for the control of a variety of insects. Once grasshoppers pick up its spores on their feet and other body parts, the fungus grows quickly inside their bodies, usually killing them within a week.
Recently, Jaronski found that an effective way to deliver the B. bassiana spores and make them attractive to grasshoppers is to mix them with raw canola oil. Black and strong-smelling, the raw oil contains higher concentrations of the fatty acids that the insects find irresistible. It's also cheaper than using refined, store-bought canola oil.
Jaronski envisions the mixture of canola oil and fungal spores being sprayed on targeted strips of rangelands from the air or on the ground. Because the oil attractant lures hoppers to the strips from a wide distance, only small amounts of the fungal spores are needed.
The other fungus, Metarhizium anisopliae var. acridum, is much more host-specific than Beauveria, affecting just grasshoppers and their close relatives. Jaronski's lab has found that Metarhizium is very infectious in most American grasshoppers and the Mormon cricket, which also causes destructive outbreaks. Coupled with the raw canola oil carrier, it could also become a valuable tool for controlling grasshoppers.
ARS is the U.S. Department of Agriculture's chief scientific research agency.
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