Distribution. Clover cutworm occurs throughout the United States except for the southeastern states. It also occurs throughout southern Canada and in Alaska. Apparently it is a native species, though it is also reported to occur in Europe and Asia.
Host Plants. This species is an occasional pest of several crops, preferring crops and weeds in the plant family Chenopodiaceae. Among vegetables attacked are beet, cabbage, lettuce, onion, pea, spinach, tomato, and turnip. Field crops consumed include alfalfa, cotton clover, flax, canola (rape), sugarbeet, and sunflower. The incidence of clover cutworm on sugarbeet explains the alternative common name, "striped beet caterpillar." However, weeds are the usual host. Weeds known to be suitable larval food plants include kochia, Kochia scoparia; lambsquarters, Chenopodium album; purslane, Portulaca sp.; and Russian thistle, Salsola kali.
Natural Enemies. Walkden (1950) reported that of field collected larvae, 12% died from parasitic Hyme-noptera, 16% from parasitic Diptera, and 22% from pathogens. Santiago-Alvarez and Federici (1978) reported Euplectrus sp. (Hymenoptera: Eulophidae) and Euphorocera tachinomoides Townsend (Diptera: Tachini-dae) attacking larvae in southern California. Other wasps parasitizing clover cutworm are Apanteles plathypenae Muesebeck, Meteorus leviventris (Wesmael) (both Hymenoptera: Braconidae), and Enicospilus mer-darius (Gravenhorst) (Hymenoptera: Ichneumonidae). Other parasitic flies include Euphorocera claripennis (Macquart) and Lespesia archippivora (Riley) (both Diptera: Tachinidae) (Arnaud, 1978). Both granulosis and a nuclear polyhedrosis viruses are known from clover cutworm larvae, and Federici (1978) reported the gran-ulosis virus to be especially important in regulating insect density. Federici (1982) also described an unusual rickettsia-like organism in clover cutworm larvae, but there is no indication that this pathogen occurs frequently.
Life Cycle and Description. There are three generations annually in Colorado and Kansas. Moth flights occur in late May, early July, and late August-early September. Pupae from the third generation overwinter. Knutson (1944) and Ayre et al. (1982a) suggested only two flights of adults in Minnesota and Manitoba, respectively, though the "second" flight period was protracted and may represent two overlapping periods of adult activity. Ayre et al. (1982a) suggested that the level of diapause induction in pupae was a critical determinant in overwintering survival in Manitoba; they speculated that if the last generation develops early in the season, diapause is not induced and the insects proceed with a generation that is not completed before the onset of winter.
Clover cutworm larva.
series of black spots immediately above the lateral band, and serves to distinguish this caterpillar from beet armyworm, Spodoptera exigua (Hubner), a species that is superficially quite similar (Capinera, 1986). Larvae attain a length of 35-40 mm at maturity. Duration of the larval stage is 16-22 days under warm conditions, but it may be extended to nearly 50 days by cool weather. (See color figure 47.)
This insect is not well-studied. Marsh (1913) gave a brief account of its biology. Walkden (1950) gave additional notes and provided a key to noctuids in the central Great Plains. Crumb (1956) described the mature larva and provided a key to larvae. The larva was also included in a key by Capinera (1986), and in a key to armyworms and cutworms in Appendix A. The moth was included in pictorial keys developed by Rings (1977a) and Capinera and Schaefer (1983). Santiago-Alvarez et al. (1979) reported a suitable artificial diet.
The larval stage defoliates plants, though it appears to favor weeds over crops. It is not a ground-dwelling species and does not sever plants at the soil surface, but climbs plants to feed on leaves. During periods of great abundance it has caused significant damage, and has been reported to assume a gregarious, dispersive "armyworm" habit.
Natural enemies, especially pathogens, generally serve to keep the population in check. Adult popula tions can be monitored with pheromone traps (Struble and Swailes, 1977a; Swailes and Struble, 1979; Ayre et al., 1982a). This species is reported to be easy to control with foliar applications of insecticides, though Bacillus thuringiensis is not often recommended. This species is a plant-inhabiting, climbing cutworm; therefore, the mechanical barriers recommended for protection of seedlings against ground-dwelling species are of little value. It is possible to deny access by ovipositing moths through use of netting and row covers, however.
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