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Scientists scrutinize corn borer numbers
MISSISSIPPI STATE -- Scientists at Mississippi State University are counting corn borers to see why the numbers are so high and to determine better ways to control the pests.
Don Parker, entomology specialist with Mississippi State University's Extension Service, said monitoring for the Southwestern corn borer has intensified this year. The corn pest has become a bigger problem in recent years as Mississippi farmers are planting more corn.
"In recent years our corn acreage has increased and the corn borer has started showing up in significant numbers to affect yield," Parker said.
Parker initiated a coordinated effort to record details of the three flights, or generations, of corn borers seen each growing season.
With the assistance of Extension county agents, farmers, agriculture industry personnel and crop consultants, Parker is setting out pheromone traps for the Southwestern corn borer. These green or white and yellow traps are about the size of a gallon bucket with a roof on top. They are hung about chest high in and around cornfields.
"We're keeping records to try to understand what normal flights look like so we can determine if a flight is normal or exceptionally high," Parker said.
Adult corn borers are attracted to the trap's scent and are captured and recorded.
"We're trying to establish whether traps can be used to determine when a field should be treated," Parker said.
Producers scout, or physically examine, a field to determine when treatments should be made. However, scouting for Southwestern corn borers is difficult because their eggs are flat and about the size of a minnow scale.
"When we start getting adults in the traps, we expect to start seeing more eggs in the field," Parker said. "That tells us to intensify the scouting in the fields."
When corn borers hatch, they move down the leaf and penetrate the stalk near the base. Corn damaged by corn borers can lodge, or fall to the ground or lean on adjacent rows of corn. This decreases yield and makes harvest difficult. Even plants that do not lodge may have significant yield loses due to the tunneling of the corn borer larvae.
The best control for corn borers is to plant Bt corn, Parker said, or corn that is bred to be resistant to certain insects. Non-Bt cornfields are treated with insecticides when corn borer numbers are high enough to warrant spraying.
"For resistance management reasons in areas where cotton is grown, only 50 percent of the corn can be planted in Bt," Parker said. "That leaves half our acreage that has to be protected through some other means."
In the past, farmers planted early to avoid the third, and largest, generation of corn borer that typically causes the lodging. With better harvest equipment, lodging is not as much of a problem as before, but the second and third generations of the pest can still cause significant damage.
"One field we examined had 76 percent of the plants infected, with an average of 14 inches of each stalk tunneled through by the Southwestern corn borers. It resulted in a 40 bushel an acre loss," Parker said.
Extension entomologist Mike Williams created a website to assist with the Southwestern corn borer monitoring. Results of the traps and other related insect information are posted online at http://www.msstate.edu/entomology/cornforum/.
For more information on trapping, contact Parker at (601) 857-2284.
Contact: Dr. Don Parker, (601) 857-2284