Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
8/22/00
Contacts:
Larry Pedigo, Department of Entomology, (515) 294-1101,
lpedigo@iastate.edu
Micheal Owen, Extension Agronomy, (515) 294-1923, mdowen@iastate.edu
Julie Todd, Extension Communication Systems, (515) 294-2405,
jtodd@iastate.edu
Herbicide-Resistant Soybean Technology Affects Insect Populations
AMES, Iowa -- Iowa State University research indicates that using herbicide-resistant soybeans with herbicide-based weed management programs can affect populations of insects.
Several herbicide-resistant and traditional soybean varieties were grown in field experiments at two locations in Iowa from 1996 through 1999. Weeds were managed by a conventional herbicide program, a targeted herbicide program with a herbicide to which the soybean cultivars were resistant or a mechanical weed management program that kept the plots weed free.
Soybean growth, yield and weed control success were assessed, and more than 100,000 insects from the soil surface and the soybean leaves were collected and identified.
The experiments showed that populations of soil surface insects were significantly affected by the type of weed management program used. Larry Pedigo, ISU entomology professor, said, "These changes in soil surface insect numbers probably were related to changes in food availability and soil moisture content that were influenced by the degree of weed control among the treatment combinations."
The research also revealed that weed management programs that provide less than complete weed control typically had greater overall foliar insect numbers than the most effective weed management programs, which allowed very few weeds. However, one pest insect, the potato leafhopper, had a preference for weed management systems with reduced numbers of weeds. Also, potato leafhoppers and bean leaf beetles seem to have preferences for certain soybean varieties.
ISU Extension weed scientist Mike Owen said, "This research illustrates the concept of integrated pest management. Controlling weeds without considering other pests is wasted effort."
This research was funded by Iowa soybean checkoff funds.
ml: isufarm
Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.