Biology and population ecology of parasites of the green cloverworm, Plathypena scabra (F.) (Lepidoptera: Noctuidae) in Iowa

Abstract

Iowa during 1970 and 1971 with the following objectives: 1) To identify the parasites of the green cloverworm. 2) To determine the distribution and seasonal occurrence of these parasites. 3) To determine the incidence of parasitism, both collectively and individually, by these parasites through space and time. 4) To determine various host-parasite relationships, i.e., stage of host attacked, whether parasitism is solitary or gregarious, and host stages in which parasite development occurs. 5) To identify the hyperparasites associated with the green cloverworm. 6) To determine the incidence of parasitism, distribution, sea sonal occurrence and host associations of these hyperparasites. 7) To determine characteristics of green cloverworm larval popula tions, i.e., relative abundance, adult sex ratio, incidence of disease and other mortality factors. An egg parasite study was undertaken with the following objectives: 1) To identify egg parasites of the green cloverworm. 2) To determine the incidence of egg parasitism and its possible role in population regulation. An intensive sampling program was conducted near Ames in 1971 with the following objectives: 1) To determine, on a weekly basis, any changes in the incidence of parasitism by individual and groups of parasite species within field populations of green cloverworms. a distance of 50 to 100 yd and then quickly alight (Hill 1925). Feral adults have been reported feeding on the nectar of blossoms of host plants (Hill 1925) and cultured moths on molasses (Sherman 1920) and water or 1% sugar solution (Pedigo et al. 1973). Mean longevity of the adult stage has been reported as 7.3 days (Hill 1925); 9.0 days (Smith and Franklin 1961); 7.9-11.1 days (Stone and Pedigo 1972), and 22.4 days (Pedigo et al. 1973). These latter workers found that females live significantly longer under greenhouse conditions than do males. Like many other noctuids, moth activity begins at dusk and con tinues into the night. Pedigo et al. (1973) observed flight to begin at ca. 3 ft-c of light and increased 3-fold (15-52 moths flying) at < 1 ft-c, during a 10-min period. Moth activity, as measured by blacklight trap catches, was shown by Pedigo et al. (1973) to occur between 8:00 PM and 2:00 AM CDT. The use of light traps to measure seasonal moth activity in Ontario, Canada, was reported by Stirrett (1931). No moths were caught in the trap between June 15 and 30, but were caught, however, between July 5 and Oct, 3 with peak moth activity between July 13 and Aug. 3. In Min nesota, moth activity was measured and reported by Knutson (1944). He collected moths as early as the 1st wk of May with heaviest flights occurring the last 3 wk of July. Pedigo et al. (1973), in Iowa, also found heaviest numbers occurring in July but reported numbers to drop substantially on Sept. 11, These latter workers reported catches to be quite erratic, though, and found no clear generation or seasonal pattern.

Life History of the Hyperparasitoid Mesochorus discitergus (Hymenoptera: Ichneumonidae) and Tactics Used to Overcome the Defensive Behavior of the Green Cloverworm (Lepidoptera: Noctuidae)

“…As reported here, C. marginiventris requires 17-18 d to mature at 24°C, whereas M. discitergus requires 20-21 d at that temperature. Lentz (1973) Simpson 1978). The egg stage lasted 2 d at 240C (Table 2).…”

“…Defensive responses of first to sixth instars of the green cloverworm were described by Yeargan & Braman (1986). M. discitergus hyperparasitizes three indigenous braconids-C. marginiventris, Diolcogaster facetosa (Weed), and Rogas no lophanae Ashmead-which in turn have attacked young larvae of the green cloverworm (Barry 1970, Lentz 1973; K, V. Y., unpublished data), These three braconids attack primarily the following green cloverworm instars: C. marginiventris, first and sometimes second instars (Kunnalaca & Mueller 1979); D. facetosa, second and third instars (Year gan & Braman 1986); R. nolophanae, third instars (Lentz & Pedigo 1974). By direct observation in the laboratory, we documented the methods by which M. discitergus captures second-, third-, and fourth-instar green clover worms, because these are the instars most likely to contain the appropriate stage of the above-mentioned primary parasitoids.…”

“…Several species, including Mesochorus discitergus (Say), hyperparasitize hymenopteran primary para sitoids of the green cloverworm, Plathypena scahra (F.), an occasionally serious pest of leguminous crops in the United States (Hill 1925, Barry 1970, Lentz 1973, So teres et a1. 1984, Daigle et a1.…”

The relation of wild parsnip, Pastinaca sativa L., to parasitoid populations associated with soybean pests in central Iowa

“…A greater wealth of documentation exists for fauna of soybean fields, including lists of predators in Iowa soybean fields, and Iowa green cloverworm parasitoids (Bechinski and Pedigo, 1981;Yeargan, 1983a, 1983b;Dietz et al, 1976;Harper and Garner, 1973;Ignoffo et al, 1975aIgnoffo et al, , 1975bKogan, 1981;Lentz, 1973;Lentz and Pedigo, 1972;McCutcheon and Turnipseed, 1981;Pedigo et al, 1981).…”