Writer: Pam Dillard, (806) 359-5401, p-dillard@tamu.edu;
Contact: Dr. Carl Patrick, (806) 359-5401, c-patrick@tamu.edu
AMARILLO – What do corn growers in at least five states have in common right now besides corn?
Entomologists say they are seeing two distinct types of borer moths active in corn fields in the Texas High Plains and Oklahoma Panhandle. Infestations also are present in production areas of eastern New Mexico and southeast Colorado as well as southwest Kansas.
According to Dr. Carl Patrick, entomologist for the Texas Agricultural Extension Service at the Texas A&M Research and Extension Center here — both the southwestern corn borer and European corn borer have been seen in fields across the region.
“Heavy infestations of these borers can severely damage the crop,” Patrick said.
Dr. Steve Amosson, Extension economist of Amarillo, stated that corn forecasts this year are expected to match the production averages for 1995-96.
“In Texas alone, if the figures equal those of the past two years, we’ll see approximately 2.1 million acres planted and 1.85 million acres harvested. The statewide yield has been averaging 108 bushels per acre over the same period,” he said.
The cycle of potential damage actually begins when borers of either type overwinter as larvae in old corn stalks and stubble. The adult moths emerge in late May and early June to lay their eggs in corn.
“The tallest corn will attract European corn borer females where they deposit their eggs, usually an average of 15 eggs on the underside of the leaves near the midrib,” the entomologist said. Eggs hatch within 3 to 7 days.
“Any size corn plant is a haven for the eggs of the southwestern corn borer,” Patrick said. An average of two to five eggs may be laid on any size corn plant, mostly on the upper surface of the leaves. Their offspring emerge in about five days.
The newly hatched larvae of both species move to the whorl, or center part of the plant where its leaves unfurl, to feed. A symptom called “dead heart” may occur if southwestern corn borer feed on the growing point of small corn plants.
Patrick noted that infestations of southwestern corn borer on whorl-stage corn seldom reach economic levels, usually running less than 3 percent. However, economic infestations may develop in corn planted next to unplowed stubble, he added.
An insecticide application to control European corn borer on whorl stage corn is justified if 50 percent of the plants are found infested with an average of at least one larva per plant.
The entomologist said the story doesn’t end here either. A second and more damaging generation of these two borers will occur in July and August.
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