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OVERTON, Texas – Armyworms are on the march in East Texas.
"This time they're everywhere, in home lawns, pastures and hay meadows,” says Dennis Smith, agriculture and natural resource agent with Texas Cooperative Extension in Gregg County. “It looks like this infestation is much larger than those in July and early August.”
Smith and other extension agents in east Texas have been getting more calls than usual this year. The outbreak has to do with the weather, said Allen Knutson, extension entomologist.
Outbreaks typically happen in the fall, and for reasons unknown are worse when rains are frequent and temperatures are cooler, says Knutson, who is based in Dallas.
Fall armyworm moths migrate in the millions, literally, northward from south Texas in the spring and summer. As part of its natural life cycle, each moth will deposit a clump composed of 50 to100 eggs on individual blades of grass.
When their egg-laying coincides with a rainfall, fall armyworms hatch in droves and immediately start maneuvers.
The eggs yield tiny armyworm larvae which feed on leaves for two to three weeks.
"Young larvae don't eat much, and infestation can easily go undetected as little damage to the pasture or hayfield is visible from a distance," Knutson says. "However, once larvae reach about 3/4-inch long, their appetites greatly increase. During the last week of their development, armyworm larvae eat 80 percent of their total food intake. For this reason, damage can occur very quickly and hay fields or pastures can seem to disappear almost overnight."
The best counterattack against an armyworm invasion is to treat with pesticides when larvae are small and have yet to do extensive damage, Knutson says. Also, sometimes using chemical controls may be a Pyrrhic victory in economic terms; the producer may control the infestation, but spend more money than would be made from the use of the pasture or harvest of hay.
"As a general guideline, if three to four or more armyworms are present per square foot, economic loss is likely and an insecticide treatment should be considered,” Knutson says. “If plants are small with few leaves, two to three larvae per square foot may be a damaging level.”
Most products approved for lawns are less concentrated than those used for production agriculture. Usually, people can venture out on the lawn as soon as the application dries.
For more information, contact the Extension office in their county, which is usually listed in the telephone directory under the "county offices" section.
More information on fall armyworms and other agricultural pests can also be found at the Texas A&M University Department of Entomology Web site at http://insects.tamu.edu/imagegallery.
Source: Texas A&M University Department of Entomology