Most corn insect control decisions are made before the planter hits the field. “Of course, decisions to control stalk borers in non-Bt corn, as well as cutworms and stink bugs in all corn, are made in-season,” says Auburn University entomologist Kathy Flanders.
“However, growers select the appropriate insecticide seed treatment and Bt corn technology long before they plant.”
Flanders says growers first need to choose a seed treatment for early season insect pests, including billbugs, white grubs, wireworms, sugarcane beetle adults and stink bugs.
“Additionally, the correct seed treatment rate is critical, especially when planting in a high risk situation, such as new ground that has been reclaimed from pasture or continuous corn,” she says. “And in no-till corn, a broadcast insecticide spray application is recommended for cutworm control.”
Next, select the appropriate Bt corn technology, Flanders says. “In addition to considering a hybrid’s agronomic and disease features, growers who have problems with stalk borers — such as southwestern corn borer, European corn borer and/or sugarcane borer — can pick one of the Bt traits that enables them to plant 80 percent Bt corn with a 20 percent refuge.”
Corn earworms are South Carolina’s most consistent corn insect pest, says Entomologist Francis Reay-Jones, Clemson University Pee Dee REC, Florence. “They typically feed on the tip of the ear, and sometimes along the side of the ear. Several newer Bt traits effectively control corn earworms.
“We also have seen more sugarcane beetles, which feed on the stem of the corn plant below the soil surface during the first few weeks after emergence. It’s more of a problem in the western part of the state.
“Fall armyworms can be our most devastating insect, particularly in non-Bt hybrids. When and where the insect migrates from Florida varies yearly. The best method to prevent fall armyworm injury is to select a Bt hybrid that is effective for the insect.”
Chinch bug infestation fluctuates annually in Arkansas seedling corn. “Often, the damage mimics herbicide injury because they feed at the base of the plant, sometimes just below the soil line,” says University of Arkansas Entomologist Glenn Studebaker.
“Some seed treatments help suppress chinch bugs early, and also control wireworms, white grubs, southern corn rootworms and fire ants.
“Insecticides easily control chinch bugs. The difficulty is getting the insecticide to the pest, which tends to be behind the leaf sheaf or below the soil line. Spray with a ground rig, using a high water volume, so the insecticide will run down the plant to the base behind the leaf sheath. And maybe direct spray toward the base of larger plants.”
Another major Arkansas pest in non-Bt corn is the southwestern corn borer. “If growers had trouble with it in 2012, they may have trouble with it again in 2013,” Studebaker says.
“Monitor the refuge with pheromone traps to determine when each generation begins to emerge so you can time a residual insecticide application.”
Sugarcane beetles are the main upcoming pest challenging Mississippi corn growers, says Angus Cat-chot, Mississippi State University Extension entomologist at Starkville. “Some hill region areas have extreme problems with this pest.
“They generally infest corn from the V2 to V4 stages. Adults feed on the stem about one-half inch below the soil surface. Often, the plant will either die or sucker out and essentially become a weed.
“There are no rescue treatments after the fact, so we address this pest with seed treatments. Poncho or clothianidine-based treatments work best, but we need to use higher rates — as high as 1,250 in some situations.
“In 2012, we tested Capture LFR in-furrow with our starter fertilizer at planting. It performed extremely well and will be a top recommendation for 2013 where sugarcane beetles threaten.”
Several new Bt lines have multiple genes that include the Viptera trait and Genuity SmartStax; they all have genes that protect against corn earworm.
“Genuity VT Double PRO corn technology has been available for several years and provides ear protection in addition to armyworm and stalk borers,” says University of Georgia Entomologist David Buntin.
“We also had some issues with sugarcane beetle. In north Georgia, corn is planted later in April, which coincides with the beetle’s emergence. The lower seed treatment rates vary in efficacy against this insect, so growers might want to consider a seed treatment with a higher rate, such as a 500 or 1,250 rate.
“Later, stink bugs occur at ear development prior to pollen shed. We need to scout and apply a foliar insecticide at threshold levels.”
The biggest decision Tennessee corn growers will have to make in 2013 will be which hybrids and Bt technologies to plant. “Many Bt trait packages are available and non-Bt corn refuge requirements vary considerably,” says Scott Stewart, Extension entomologist at Jackson.
“Bt technologies were introduced to control corn borers, either southwestern or European corn borers, and they all work very well. Newer technologies enable growers to reduce their refuge requirements in many cases.
“Southwestern corn borer in parts of our state remains a significant pest, as well as the European corn borer. Besides Intrepid and pyrethroid insecticides, new insecticides for controlling corn borers and other caterpillar pests in non-Bt corn include Belt, Prevathon and Besiege.
“We normally don’t spray a lot of corn for pests other than corn borers, but we need to remain alert for sugarcane beetle, cutworms and several other pests that occasionally cause problems.”