Effects of Serratia marcescens on the F-1 generation of laboratory-reared Heliothis virescens (Lepidoptera : Noctuidae)

The effects of the bacterium Serratia marcescens (Bizio) was investigated o n the F, generation of laboratory-reared Heliothis virescens (F.). There wa s no difference in adult male or female longevity (i.e., parental generatio n) for individuals inoculated with S, marcescens as larvae (Serratia treatm ent) and those that were free of the bacterium (control treatment). However , the number of eggs laid and the prevalence of eclosion of eggs from Serra tia treatment adults were reduced relative to control treatment adults. A v ery low number of F, Serratia treatment eggs exhibited signs of infection, but a higher prevalence of mortality was observed for F, larvae (n = 2,888) for the Serratia (3.5-4.6%) than for the control (1.1-1.5%) treatment. No S. marcescens was isolated from dead control larvae: whereas, 48-54% of dea d F, larvae for the Serratia treatment were positive for the bacterium. How ever, there was no significant difference in larval weights between treatme nts. There were also no differences in either mortality or weight of F, mal e pupae between treatments, but F-1 female pupae were significantly smaller and prevalence of mortality was higher for the Serratia treatment. Serrati a marcescens was not isolated from any of the control F1 pupae, but 6% of p upal cadavers for the Serratia treatment were positive for the bacterium. N o S, marcescens was recovered from the meconia of any of the F-1 adults (n = 2,600) regardless of treatment, and there were no differences in adult we ights between treatments. Although sublethal effects of S, marcescens were detected, the impact and prevalence of the bacterium were tremendously redu ced over the F, generation in the absence of all but the most basic managem ent strategies.