Distribution. Bronzed cutworm is widespread in distribution, occurring throughout the United States except for the southernmost tier of states. It also is found in southern Canada, from the Maritime Provinces to British Columbia. Despite the broad distribution of this species, its economic impact is limited to the eastern portion of its range, as far west as the Rocky Mountains. Also, it rarely is known to be damaging south of Kansas, Missouri, and Virginia. It is a native species.
Host Plants. Bronzed cutworm larvae feed on grasses and such grain crops as barley and wheat. It is most frequently considered a pest of pasture and lawn grasses, especially Poa spp., and occasionally it damages field crops such as clover and sugarbeet. It commonly damages corn in the midwestern states, and when preferred plants are exhausted it may feed on other vegetables. On occasion, larvae also are observed to climb fruit trees and feed on the buds and leaves.
Natural Enemies. Parasitoids and predators, though observed, seem less significance as mortality factors than viral diseases. Wasps known to attack bronzed cutworm include Rogas terminalis (Cresson), Apanteles rufocoxalis Riley (both Hymenoptera: Braco-nidae), and Campoletis oxylus (Cresson) (Hymenoptera: Ichneumonidae). Among parasitic flies reared from bronzed cutworm are Aplomya trisetosa (Coquillett), Euexorista futilis (Osten Sacken), Phryxe pecosensis (Townsend), and Tachinomyia variata Curran (all Diptera: Tachinidae). Western yellowjacket, Vespula pen-sylvanica (Saussure), is reported to prey on bronzed cutworm moths (Warren, 1990). A polyhedrosis virus has long been considered to be an important mortality factor (Walkden, 1937), but a granulosis virus also has been reported (Steinhaus, 1957).
Life Cycle and Description. There is a single generation per year over the entire range of this insect.
Adults are present in the autumn. In New York, moth flights consistently occur in September (Chapman and Lienck, 1981), in Minnesota they occur in late August and early September (Knutson, 1944), and in the central Great Plains their flights occur in September and October (Walkden, 1950). The eggs overwinter; however, egg hatch occurs early in the year, often in January and February. Larvae complete their development in April or May, and become quiescent until July or August, when pupation occurs.
Bronzed cutworm larva.
head is orangish-brown. The first four instars differ in background color, in that they are green instead of bronze, but also are marked with longitudinal stripes as found in the latter instars. (See color figure 44.)
Detailed description and biology of bronzed cutworm was given by Crumb (1926) and Walkden (1937). A bibliography was published by Rings et al. (1974a). A comprehensive key to larvae of the Noctui-dae, including this species, was presented by Crumb (1956). It is also included in less inclusive keys for caterpillar pests in Nebraska (Whelan 1935) and Colorado (Capinera, 1986), and in a key to armyworms and cutworms in Appendix A. Moths are included in pictorial keys by Rings (1977a) and Capinera and Schaefer (1983).
Larvae are defoliators, and consume the leaves and stems of young plants. As they are present early in the year they normally damage only early-season plants.
Larvae have been controlled successfully with applications of residual insecticides to the soil and foliage. Bacillus thuringiensis is not often recommended for cutworms. Although there seems to be no report of experimentation with baits, treated bran would likely prove effective.
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