Gypsy moth (Lymantria dispar) larval development and survival to pupation on diet plus extractables from green ash foliage

Gypsy moth, Lymantria dispar L., rate of larval development, molting, pupal weight and survival were studied on an artificial diet containing different concentrations of green ash ethyl acetate extractables (EtOAc Errs). Insects were reared on experimental diets from egg to pupa. Addition of EtOAc Exts to artificial diet significantly prolonged larval development and reduced their survival compared to larvae reared on control diet. Weights of pupae were significantly reduced when larvae were reared on diet containing the lowest dosage of EtOAc Exts (i.e., 0.01%) versus on control diet. EtOAc Exts in diet (e.g., 0.01, 0.06 and 0.24%) frequently caused incomplete ecdysis which invariably resulted in larval death. Impaired feeding, locomotion and excretion are likely causes of death. The combination of these results with our earlier findings of repellents and feeding deterrents against gypsy moth larvae (GML) in green ash foliage shows that the non-host status of green ash to the highly polyphagous GML involves three orders of chemical defense: repellents, feeding deterrents and inhibitors of nutritional and developmental physiology. As the insect becomes sequentially exposed to these orders of defense, it incurs higher costs because the adverse effects become less reversible.