Naturally-Occurring and Synthetic Loline Alkaloid Derivatives: Insect Feeding Behavior Modification and Toxicity²

Methanol extracts of tall fescue plants (Festuca arundinacea Schreb.) infected with an endophytic fungus (Acremonium coenophialum Morgan-Jones and Gams) contain loline alkaloids which deter feeding and are toxic to insects. This study was conducted to determine the effect of several naturally-occurring and semi-synthetic loline alkaloid derivatives on insects. The influence of these compounds on the feeding behavior and weight of fall armyworm larvae, Spodoptera frugiperda Smith, and European corn borer larvae, Ostrinia nubilalis Hübner, was evaluated using two-choice, diet-incorporated feeding behavior modification bioassays. Toxicity of these compounds to greenbugs, Schizaphis graminum Rondani, was evaluated and compared with the toxicity of the insecticide nicotine sulfate. Fall armyworm larvae were more susceptible, in terms of feeding behavior modification and reduced weight gain, to specific loline derivatives than European corn borer larvae. N-acetyl loline appeared to show toxic effects, in terms of reduced larval weight in the absence of feeding behavior modification, toward both fall armyworm and European corn borer larvae. Several of the naturally-occurring loline alkaloids, namely N-formyl loline, N-acetyl loline and N-methyl loline, had LC₅₀ values against apterous greenbug adults similar to nicotine sulfate.