The leaf beetle Diorhabda elongata Brullé (Coleoptera: Chrysomelidae) has been introduced as a biological control agent for saltcedars, Tamarix spp., an exotic, invasive weedy tree in the western United State. Gas chromatographic (GC) analysis of volatiles collected from feeding male or female beetles, or saltcedar foliage alone, showed two components produced almost exclusively by males. These compounds elicited responses from antennae of male and female beetles in GC-electroantennographic detection (EAD) analyses. The compounds were identified as (2E,4Z)-2,4-heptadienal (1) and (2E,4Z)-2,4-heptadien-1-ol (2) by GC-mass spectrometry (MS), and confirmed with authentic standards. The two compounds were also detected at trace levels from feeding females and foliage controls, but the amounts from feeding males were 8-40 times higher, typically 55-125 ng per day per male. The amounts of 1 and 2 in collections from females did not differ significantly from amounts collected from control foliage. In field trials, 2 as a single component was as attractive as a 1:1 blend of 1 and 2. Compound 1 as a single component was more attractive than controls, but much less attractive than 2 or the blend. Males and females were attracted in about equal numbers, indicating that this is an aggregation pheromone.

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.

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The control of insect pests and invasive weeds has become more species-selective because of activity-guided isolation, structure elucidation, and total synthesis of naturally produced substances with important biological activities. Examples of isolated compounds include insect pheromones, antifeedants, and prostaglandins, as well as growth regulators for plants and insects. Synthetic analogues of natural substances have been prepared to explore the relationships between chemical structure and observed biological activity. Recent scientific advances have resulted from better methods for the chemical synthesis of target compounds and better analytical methods. The capability of analytical instrumentation continues to advance rapidly, enabling new insights.