Cool Weather Fungus Could Put Potato Pest on Hot SeatBy
Spraying potato plants with the fungus Beauveria bassiana can kill
hungry Colorado potato beetles so less insecticide is needed. The rub: Summer's
heat can squelch Beauveria before it gets started.
Studies conducted by Agricultural
Research Service microbiologist Phyllis Martin and co-workers last summer in
Maryland suggest Beauveria will perform best in early spring, or cooler
regions like Maine. Summer temperatures that climb above 86 degrees Fahrenheit
can kill the fungus or prevent it from germinating into forms that infect and
kill potato beetles.
Martin reports on her findings at today's American
Society for Microbiology meeting in Atlanta, Georgia. She and ARS
colleagues Robert Schroder and Ashaki Shropshire conducted field studies on
Maryland's Eastern Shore and at Beltsville, Md. Their work is part of an
ongoing project with Polish and Czech Republic scientists. The goal: develop an
integrated approach to managing the beetle, which resists some insecticides.
The pest costs U.S. potato, tomato and eggplant growers about $150 million
annually in losses. It's just as destructive abroad. Beauveria is one
of several natural alternatives scientists are testing. Other alternatives
include Bacillus thuringiensis bacteria, beneficial insects and a
Last year, Martin's group treated half-acre potato plots with a registered
commercial Beauveria strain from Mycotech Corp. They treated each plot
four separate times from May to July. Overseas, their colleagues followed suit,
later reporting an 84 percent drop in larval beetle populations. But in
Maryland, no such reduction occurred.
By growing Beauveria in test-tube experiments at ARS'
Insect Biocontrol Laboratory
in Beltsville, Martin concluded temperature was the deciding factor. In
Maryland, Beauveria often faced 100-plus degree temperatures. But
Poland's average daytime temperature of 74 degrees F. proved more forgiving,
allowing the fungus to survive on plants longer and kill leaf- eating larvae.
Scientific Contact: Phyllis Martin, USDA-ARS Insect Biocontrol
Laboratory, Beltsville, Md., (301) 504-6331, fax (301) 504-6973,