News release, October 12, 1998, effective immediately.
For media inquiries, contact Caroline Booth Lara, Communications Specialist, (580) 224-6379.
  email: cblara@noble.org

Attack of the Armyworms

As if landowners in Southern Oklahoma and North Texas haven't had enough problems this summer with drought, high temperatures and grasshoppers, they now have something else to worry about — fall armyworms.

Damaging populations of the pests have been reported on several Noble Foundation demonstration farms in Southern Oklahoma as well as by area land owners and managers, and NF specialists warn the worms are doing significant damage to newly established small grain pastures and new growth in bermudagrass fields.

"In several instances, entire small grain fields are having to be replanted because the armyworms have eaten the seedling leaves as they emerged from the soil," said Hugh Aljoe, NF forages specialist.

He urges producers to check their small grain pastures daily while stands are emerging and becoming established.

"A fall armyworm infestation can devastate a new small grains crop within hours," Aljoe said.

Armyworms are small green, brown or black caterpillars with an inverted "Y" on the head, about 0.5 to 1.5 inches long. They feed continuously, but are most active and easily seen during the early morning and late evening.

Producers also should watch for the presence of small white or pale gray moths in pastures just before dark. This moth lays eggs from which armyworms hatch. Fall armyworm damage is often first noticed around the field margins near fence rows with overgrown vegetation or wooded borders, Aljoe said.

Fall armyworms will likely be present from August until frost. Populations can reach damaging proportions following fall rains, while temperatures are relatively warm. As temperatures decrease, the life cycle of armyworms slows. The destructive caterpillar stage of the army worm lasts two to three weeks. Although prefering immature growth on grass, they will eat new growth on most any plant. Chemical treatment may be the only option to destroy the pests when armyworm populations reach 4 to 5 armyworms per square foot, or two to three armyworms per row foot on plants 2 to 4 inches in height. However, chemical treatment may not always be economically feasible.

Two types of chemical treatment are available: 1) treating the plants where the pests will be feeding, and 2) killing the caterpillars on contact.

Among the most common leaf-treatments are Sevin and Lorsban SG. Sevin is labeled for both wheat and pasture, and does not have a grazing restriction. Lorsban SG kills on contact and by ingesting the chemical, and is labeled on wheat only.

Chemical treatments that kill on contact include Lorsban SG, Karate, methyl-parathion, parathion, and malathion. Lorsban SG has a grazing restriction of 14 days, methyl-parathion and parathion both have 15-day grazing restrictions, Karate has a 30-day grazing restriction, and malathion has no grazing restriction. Most contact pesticides have little or minimal residual affect after initial application.

The insecticide Confirm has been allowed under Section 18 for fall armyworm control in pasture. It provides excellent control and a 21-day residual with no grazing restrictions.

Regardless of the treatment or chemical being used, all label instructions should be read and followed.

Significant numbers of armyworms may reappear within five to seven days after treatment. Regular monitoring of treated and untreated fields should continue until the region experiences cooler temperatures and plants are more advanced in their growth.

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(FYI — The Noble Foundation is a privately funded, nonprofit organization headquartered in Ardmore, Okla. The Foundation conducts agricultural and plant biology research; provides grants to numerous other charitable and educational organizations; and assists farmers and ranchers through educational and consultative programs.)

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