Armyworms invade pastures, cropland

SALEM, Ohio – Ohioans are watching the march of armyworms as their invasion draws near.

Farmers in Missouri, Texas, Illinois, Indiana and Kentucky have seen extensive feeding damage from the armyworms, so named because they appear to march in unison across the fields, devouring all green leafy plants in their path.

Dan Digman, Ohio State University Extension entomologist, says although he doesn’t foresee any problems, farmers won’t see the armyworm larvae in Ohio for another couple of weeks.

“The adults are here. I wouldn’t say I’ve seen an abnormal number though,” said Digman. “The adults are laying eggs and we won’t see any feeding damage for another two to three weeks.”

High populations.

Why the armyworm population is so high in neighboring states remains a mystery. Many state entomologists credit the early spring weather. In Indiana, Purdue entomologists caught 670 armyworm moths in black light traps. They say typical numbers are usually in the 20s at the most.

The worms range in size from a quarter-inch to 11/4 inches in length. The worms consume emerging corn, wheat, rye and other tall growing grasses. When armyworms consume all available green leaf material in a field, they’ll move into adjacent fields. Urban lawns could also provide a succulent dinner for the worms.

The feeding frenzy ends when the larva buries itself in the soil to pupate. In late summer, the adult moth emerges and begins laying eggs.

Inspect fields.

Farmers should inspect their fields for signs of armyworm damage. If worms aren’t seen, farmers should look for damage to edges of leaves and for droppings on the ground. Farmers should also look in soil cracks or under surface residue to actually find the worms.

Controlling the worms in row crops may be done with many different products and pesticides. However, farmers need to be aware of harvest restrictions on the label. Pastures should recover as the worms move away in search of more leaf tissue. Depending on the extent of the damage, cattle may need moved to other pastures to let the grass rejuvenate.

Natural controls of the armyworm are a wasp that lays eggs on the worms and a fungus that kills the worms.