Farmers are being warned of the presence of armyworms in several parts of New York State, including northern and western counties.

Experts said that the offspring of this infestation, expected next month, could cause significant crop damage.

State Agriculture Commissioner Darrel Aubertine said the Department of Agriculture and Markets has received numerous reports from farmers and the New York State Integrated Pest Management (IPM) Program have verified that true armyworms have severely impacted parts of New York State, especially in western New York counties. Additional reports have established the presence of armyworms in northern New York, the Finger Lakes and Eastern New York.

Homeowners and farmers are encouraged to watch grass and corn fields for signs of infestation. According to New York State IPM Livestock & Field Crops IPM Coordinator Keith Waldron, a second generation can be expected and may result in further damage in July.

New York's last significant infestation was in 2008, and prior to that in 2001. By some accounts, this year's infestation is surpassing those.

The pest’s moth overwinters in the South and, in some years, flies up to New York laying eggs that hatch into worm-like caterpillars. It is a migratory pest and the unusual spring weather may be responsible, at least in part, for this infestation.

Armyworms got their name because they can move in a mass, marching in lines from one destroyed field to their next feeding ground. They have been found in New York in small grains, corn, mixed stands of alfalfa, turf grass, grass and hay fields, but have been known to also infest various vegetables, fruits, legumes, and weeds, including beans, cabbage, cucumbers, lettuce, onions and peas.

In their early stages, armyworm larvae appear smooth, cylindrical in shape and are pale green to brownish. Mature larvae are smooth and marked with two orange, white-bordered strips on each side. True armyworm ranges in size from 1/8 inch to 1.5 inches long and overwinter as partly grown larvae.

Preferring to feed at night, armyworms devour succulent foliage. By feeding on leaves and occasionally stems, they can severely damage seedling stands. Because they feed at night, armyworms may inflict much injury before they are detected. Having exhausted a current food supply, the worms migrate as an "army" to new host plants. Fields adjacent to or harboring lush grass are most commonly attacked.

Parasites, various diseases, insect predators, and birds usually keep armyworms under control except after cold, wet springs. When practical, cultural methods, such as disking large areas, can help reduce future armyworm populations by exposing the pupae to natural enemies and hot weather. However, since armyworm moths are strong fliers, most areas will be subject to constant reinfestation.

Armyworms are easily controlled chemically when buildup occurs, but both the armyworm pest and the specific crop should be on the insecticide label before using the product. Monitoring is important prior to spraying as treatment should be sought only when pest levels would cause economic damage.

In a newsletter released on Monday, Cornell Cooperative Extension suggests that a storm system about a month ago brought adult armyworm moths to Western New York. After mating and egg deposition the hatching larvae have begun feeding.

Reports from Erie, Genesee, Orleans, Livingston and Monroe Counties demonstrate the feeding capacity of these caterpillars, according to Walt Nelson CCE-Monroe County Agriculture Program Leader. There are also reported armyworm sightings in Eastern New York.

Cereal grasses, including wheat and rye as well as corn and alfalfa are reported targeted by the armyworm. Several home owners and golf course superintendents tell of turf grass consumed by the insect. After consuming all those plants in their path they often move into vegetable fields, including sweet corn. They are nocturnal feeders, spending the day under plant residue on the soil surface.

The gray-green to tan larvae is 1 ¾ inches long, at maturity. Characteristic longitudinal orange stripes run the length of the body. Fortunately there are several pest management options farmers have in combating the insect. A field perimeter spray late in the day is often sufficient to protect the entire field, reducing pesticide use with this integrated pest management strategy. There are usually several generations each year. Fortunately, there are several natural enemies that should rapidly increase in number to bring into check future generations in the area.

For more information regarding armyworms in New York and how to detect or combat them, contact your local Cornell Cooperative Extension agent (www.cce.cornell.edu).

Images from Indiana University.