What is in this article?:
- Rising prices make corn insect control more beneficial
- Can tolerate damage
- Rootworm spreading southward
• There are a lot of new traits, herbicide and insect-tolerant traits, and it’s getting even more complicated as new products come on line.
• Five to eight different genes have increased the price of a bag of seed over conventional corn by up to $70 to $75 per bag.”
• There is no key insect pest of corn in Georgia causing serious damage in most fields every year.
Can tolerate damage
Corn can tolerate considerable leaf defoliation and some ear and kernel damage before significant yield loss occurs, he says. “Therefore, insecticide use in field corn in Georgia historically has been limited and aimed mostly at soil and seedling pests,” says Buntin.
Insect pest management in field corn, he says, consists of two approaches: 1.) prevention of insect damage by crop management and preventive insecticide use in high-risk situations; and 2.) regular monitoring of the insect-pest infestations and treatment on a field-by-field basis as needed after plants have emerged.
“Historically low commodity prices for corn made routine preventive use of insecticides in Georgia a questionable practice. However, recent robust grain prices and availability of low-cost seed treatments make active pest management with insecticides more beneficial,” says Buntin.
Corn fields should be checked about two weeks after planting to verify that plants are emerging and to determine the kinds and numbers of insects that may be present and initiate controls if necessary, he says.
“Inspect at least 10 whole plants at each of 10 different locations for average sized fields. Sample the entire field. Yield loss occurs when as few as 10 percent of plants are destroyed or damaged so severely as to prevent normal stalk and ear development. Look for insects around the plants, on the plants, and in the soil around the stem and roots.
“Also, look for dead, dying and lodged plants. If insects are present, heavy damage to the young seedlings can occur in two to three days if not controlled, says Buntin.
Growers should check late-planted corn very carefully for the lesser cornstalk borer by looking for larvae (usually in a silken tube) boring into the plant just at the soil line.
Once corn plants reach the five to seven-leaf stage, they are large enough to escape damage by most seedling pests, says Buntin. Most insects of importance during the whorl stage defoliate the whorl and leaves. These include grasshoppers, armyworms, corn earworm, cereal leaf beetles and others.
Stalk-boring and root-feeding insects can be a problem on corn at mid-season, says Buntin. European corn borer, Southwestern corn borer and Southern cornstalk borer are caterpillars of moths that tunnel inside corn stalks during the whorl and ear fill stages.