Realized and potential fecundity, egg fertility, and longevity of laboratory-reared female beet armyworm (Lepidoptera: Noctuidae) under different adult diet regimes

Abstract

Longevity, duration of the oviposition period, realized fecundity, potential fecundity, and egg fertility of the beet armyworm, Spodoptera exigua (Hübner), were examined in the laboratory under three different adult diet regimes. All parameters were significantly reduced for the water-only diet compared with 10% honey or sucrose diets, except fertility, which could not be measured after 5 d because of high mortality of water-fed females. Oviposition was highest the night after mating and decreased in a logarithmic manner thereafter. In the carbohydrate-fed moths, 92% of lifetime realized fecundity occurred by the fourth night of oviposition. Although our data indicate that carbohydrates in the adult diet can increase realized and potential fecundity, most of the lifetime complement of oocytes (91%) is present at the time of eclosion from the pupa. Pupal weight was significantly correlated with lifetime potential fecundity, explaining 37-66% of the variation among moths depending on adult diet, and this effect was substantial. Taken together, our results suggest that the bulk of variation in realized fecundity is generated in the larval stage, provided suitable oviposition substrate is available for the adults. This information will be important in understanding population dynamics of beet armyworm and to improving our ability to predict population outbreaks from sampling data.