| Partial, age-specific life-tables were constructed for generations of western yellow-striped armyworm (Spodoptera praefica Grote) in a nontreated hay alfalfa field near Davis, California. Generation mortality was highest (ca. 96%) during the egg-small larva age interval. Cage exclusion studies and observations indicated that predators were largely responsible for this mortality. The predators in question included adults and nymphs of Nabis spp., Geocoris spp. and Orius tristicolor (White), adults of Collops vittatus (Say), larvae of Chrysopa carnea Stephens, and the otherwise phytophagous species, Lygus hesperus Knight. Parasitization and disease (NPV) comprised a relatively small portion (ca. 2-4%) of the generation mortality. The major parasitoid species reared from the field collected larvae of S. praefica were Chelonus insularis Cresson, Hyposoter exiguae (Viereck), and Apanteles marginiventris (Cresson). The results of this study have implications for classical biological control, particularly the feasibility of biological control in temporary agroescosystems and the utility of predators in biological control. The results indicated that, contrary to the prediction of Conway (1976), so-called "r-pests" may be controlled by what would appear to be "r-selected natural enemies". |
