Pink Boll worm (Lepidoptera: Gelechiidae), Cabbage Looper, and Beet Army worm (Lepidoptera: Noctuidae) Pupal Susceptibility to Steinernematid Nematodes (Rhabditida: Steinernematidae)

Abstract

Laboratory studies were conducted to determine the susceptibility of pink boll worm, Pectinophora gossypiella (Saunders), cabbage looper, Trichoplusia ni (Hubner), and beet army worm, Spodoptera exigua (Hubner), pupae to 2 species of entomopathogenic nematodes, Steinernenia riobravis Cabanillas, Poinar & Raulston and S. carpocapsae (Weiser). Uninjured pink boll worm pupae or pupae with a completely formed integument were not susceptible to nematode infection (>95% moth emergence). Pink boll worm pupae with pininflicted punctures, injuries from handling or incomplete integument formation, were susceptible to nematode infection. Uninjured cabbage looper and beet army worm pupae were susceptible to infection by both nematode species. Spiracular orifices of cabbage looper and beet army worm were elliptical in shape and larger than the circular shaped pink boll worm spiracular orifices. Spiracular orifice surface areas of cabbage looper pupae were larger than beet army worm surface areas and beet army worm were larger than those of pink boll worm. The results suggest a partial explanation for the lack of susceptibility of pink boll worm pupae to nematode infection.