LUBBOCK - Farmers growing corn on the South Plains should scout their crop soon for evidence of Southwestern corn borer eggs, said a Texas Agricultural Extension Service integrated pest management agent.
“The second generation Southwestern corn borer recently began laying eggs in Castro County. Even though egg counts were relatively low the week of July 19, we will likely see increasing egg numbers in the next two weeks,” said Johnna L. Patterson, Extension IPM agent for Castro and Lamb counties. “As a result, producers should plan to scout their fields soon.
“Second generation Southwestern corn borers usually begin laying eggs after plants have tasseled. Most of these eggs will be found on the plant’s middle seven leaves from four leaves below to two leaves above the ear leaf.”
These borers often lay single eggs, but masses of two or more eggs are not uncommon. The eggs overlap each other, much like fish scales or roof shingles. Freshly-laid eggs are creamy white in color, while day-old and older eggs sport three red-colored bands. The eggs usually hatch in about five days, the agent noted.
“Hatchling larvae from these eggs will feed behind the plant’s leaf collars and ears, and beneath the shucks of the primary ear,” she said. “Older larvae will bore in the stalk and continue feeding on the plant. When fully mature, these dull-white larvae are about one inch long and have a regular pattern of raised black dots over their bodies.
“As corn plants reach maturity, these larvae prepare to overwinter in the base of the stalk by girdling the plant one to six inches up from the soil surface. The weakened stalks make the plants vulnerable to wind lodging. Blown-over plants are difficult to harvest, and yields can suffer if enough plants are affected.”
Producers should consider an insecticide treatment for this pest when scouting reveals that 20 to 25 percent of plants in a field are infested with eggs or newly-hatched larvae, the agent said.
“Scouting is the only reliable way to check the crop for eggs and larvae, and to determine whether an infestation warrants an insecticide treatment,” Patterson said. “Producers should consult their Extension agent or crop consultant to correctly time an insecticide treatment to achieve the best control.”
Farmers with Internet access can keep abreast of crop pest numbers, control recommendations, and current growing conditions across the South Plains by accessing the weekly Focus newsletter and IPM county newsletters available at: http://lubbock.tamu.edu/ipm/ipmcentral.html.
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