The two most important corn borer pests are the sugarcane borer and the southwestern corn borer.
LSU AgCenter agents and specialists are using "trapping" technology to track the southwestern corn borer and help prevent major damage to Louisiana’s corn crop.
Dr. Jack Baldwin, an LSU AgCenter entomologist, said the demonstration project designed to evaluate corn borer damage has been conducted each year since 2004. This year pheromone traps were placed in seven fields in three parishes as part of this grant-funded effort.
Baldwin explained that the so-called sugarcane borer infests corn in northeastern Louisiana and south-central Louisiana and is now the predominant corn borer pest in the state. The southwestern corn borer occurs mainly in the upper parishes of Northeast Louisiana and does not have a statewide presence, he said. In addition, the European corn borer occasionally is found in northern Louisiana, but Baldwin said is not a serious problem.
"Numbers have recently declined in parishes where the southwestern corn borer was once a serious problem – probably due to the adoption of Bt corn and other pest management practices," Baldwin said.
This year traps funded by a $4,000 grant from the Louisiana Soybean and Grain Research and Promotion Board were placed in three fields in East Carroll Parish, two fields in Madison and two in West Carroll. In addition, agents in Franklin and Richland also maintained traps.
"Traps have told us this year that southwestern corn borer populations have been relatively light," Baldwin said.
In addition to the traps monitoring borer populations, LSU AgCenter faculty members conducted a comparison test of Bt and non-Bt corn at one of the pheromone trap sites.
Corn borer larvae damage corn by boring into the stalk and then boring up and down the stalk. This disrupts the flow of water, nutrients and other elements required to sustain plant growth and develop an ear of corn.
"Damage to the stalk can even sometimes cause plants to lodge," Baldwin explained, adding that corn plants are most susceptible at and after the tassel/silk (reproductive) stages and that borers can sometimes even bore into the ear while it is developing.
On the other hand, borers are not considered to be very damaging in whorl-stage (pre-tassel) corn, because of low numbers and feeding on the foliage. But there are times when they cause "dead heart" condition – if they feed on the growing point deep in the whorl.
The LSU AgCenter’s pheromone traps are located in parishes considered to be key to determine moth counts and watch for population increases of the southwestern corn borer.
Specialists also provide recommendations on Bt corn varieties, which often are tested in parish corn variety trials. Other recommendations for minimizing damage include early planting, recommended thresholds and insecticides, and post-harvest crop destruction, Baldwin said.
In addition to the demonstrations, LSU AgCenter researchers test Bt technology and other pest management strategies to determine effectiveness against corn borers and other corn pests, and they monitor corn borer populations for early signs of resistance to Bt.
"Bt corn has been planted on 40 percent to 45 percent of total state corn acreage," Baldwin said regarding the effectiveness and popularity of that pest management technology.
In addition to the problems the pests can create in corn, corn borers also can be a serious pest in grain sorghum, especially if it is planted late, Baldwin said.
"Corn borer moths migrate from corn as it dries down and then migrate to nearby fields that are still susceptible," he said.–Tom Merrill
(This article was published in the 2008 edition of the Louisiana Soybean & Grain Research & Promotion Board Report.)