During the past three weeks, high numbers of true armyworm moths have been captured in the southern states of Kentucky and Arkansas. Similarly, high moth numbers have been observed in southwest Missouri. Numerous storms and high winds often transport moths into the state from more southern regions of the U.S. The risk of true armyworm damage is more common in southern Missouri areas, although all areas of the state can develop problems depending on where moths land and lay eggs.

Armyworm. Photo provided by Wayne Bailey

Crops most at risk of true armyworm damage are tall fescue seed fields, fescue and other grass pastures, and wheat. True armyworm overwinter as large larvae and quickly develop into moths in early spring. True armyworm moths are light tan to grayish-brown in color with a pinkish-white spot located near the center of each forewing. Each female moth may lay 2000 pale green eggs, usually on green vegetation. Larvae emerge within a couple of weeks and feed on grasses and cereal crops for three to four weeks. Larvae are yellowish-brown in color with smooth hairless bodies and three dark longitudinal lines running down each side and back. A distinguishing characteristic is the presence of four pairs of abdominal prolegs, each with a dark triangle located near the tip of the leg. Although two to four generations may occur in Missouri each year, the first generation is responsible for most damage to tall fescue and wheat.

Armyworm larvae avoid light and spend most daylight hours hiding deep in plant residues near the soil surface. Feeding generally occurs at night with plants being defoliated from the soil surface upward. If larvae devour available food in one area, they will readily move (march) in mass to another field of grass or wheat. This behavior is responsible for the name armyworm. Although no reports of armyworm damage have been reported in Missouri at this time, producers of tall fescue seed, tall fescue pastures, and wheat are encouraged to scout for the presence of armyworm larvae or foliar damage to host crops. We will continue to monitor fields statewide for the presence of Armyworm. Photo provided by Wayne Bailey

Wayne Bailey
Entomology
573-882-2838 office
573-864-9905 cell