Larry Stalcup

September 1, 2011

3 Min Read


Mid-summer drought held down many southern corn yields for 2011. But even though the heat slowed insect damage, there’s no way growers can relax on insect control. And they’re waiting on new chemistries to broaden their bug-battling ability.

Southern insect pests are relentless in their attacks on crops. And corn is among their favorite targets. While northern growers, too, have their bug breakouts, southern growers normally face heavier pressure and for longer periods, say Rogers Leonard, LSU AgCenter entomologist.

These pest problems can range from massive spider-mite infestations spawned by a Texas drought, to sugarcane beetle (borer) invasions in the Carolinas and Louisiana. There are usually plenty of insecticides to control them, but you have to be ready to fight before it’s too late.

Cutworms are common early season problems and require pyrethroid applications at planting. Stink bugs and corn earworms at silking are also problems and may also require pyrethroid apps if heavy pressure occurs.

Even with Bt helping control earworms, heavy pressure can still force growers to spray a pyrethroid. The 2011 corn year was so dry for many that they couldn’t determine whether or not Bt-stacked hybrids worked.

Most growers go with an insecticide-fungicide seed treatment. Leonard says insecticide-treated seed can help with early insect pest problems, such as chinch bugs, which were a problem on seedlings early on in 2011.

“Seed treatments usually control them. They usually are not yield-limiting pests unless there is heavy pressure,” he says.

Southern corn rootworm, wireworms and white grubs are still among the most common early season insect pests. In 2011 the sugarcane beetle injured corn seedlings and required some fields to be replanted, Leonard says. He adds that later in the year, a complex of caterpillar pests, such as armyworm, corn earworm, southwestern corn borer and sugarcane borer, feed on leaves, stalks and grain.

“The sugarcane beetle has been more of widespread problem than one may realize, with reports of damage in Mississippi and Tennessee cornfields.” Leonard says. He advises growers to be ready for them in 2012. “They carve out the root system and can kill plants as tall as 12 in.”

Entomologists at North Carolina State University (NCSU) say the beetles feed below the soil surface and chew into the outer walls of lower stalks, leaving large ragged holes. Seedlings suffer the most damage and are often killed when the beetles destroy the growing point.

Damage occurs primarily from April 15 to June 15 in Gulf Coast states and from late April to late June in Virginia and North Carolina, NCSU entomologists say.

Leonard says southern growers are looking toward new SmartStax and Viptera Bt corn lines, in which combinations of Bt proteins from the former YieldGard and Herculex technology is pyramided with novel Bt proteins, as well as wider tolerance to more herbicide chemistry in stacked packages.

“Eventually, these tools should help provide excellent control of many caterpillar pests and provide more options for herbicide-use strategies,” he says.

 “We have greater caterpillar pest pressure for a longer time. We were happy to see that Monsanto and Pioneer have developed new corn-breeding and technology development facilities for the South,” Leonard says.

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