Chemical Communication in Insects: Background and Application

The ultimate practical goal of pheromone research on insect tsT to place the communication system on a molecular basis and to use the knowledge to detect, survey, trap, or disrupt the population. The ideal procedure is to identify quantitatively all of the components and to use all or some of them as synthesized chemicals in the emitting device in the field. Some of the problems and pitfalls are discussed. Detection and survey traps are widely used. Several successful demonstrations of mass trapping and of disruption have been carried out. Given cooperation of government agencies and industry, pheromones will surely be used as one component of integrated pest management. DECISIONS, PROCEDURES, PITFALLS, AND QUESTIONS In 1967, after three years of working with bark beetle pheromones, my colleagues and suggested that the following rigorous protocol be generally adopted:1 1. Understand the behavior of the target insect in the field and develop a laboratory bioassay to mimic the important facets of the attractant or aggregation behavior the key facet being attraction over a distance. 2. Produce enough starting material to permit chemical identification of the active components. We considered extraction of insect bodies or glands, excreta, or trapping of emitted volatiles. 3. Fractionate the material, following each step with a laboratory bioassay. Test combination of fractions for additive or synergi stic effects. 4. Identify the individual active components by means of spectrometric and microchemical techniques. 5. Confirm postulated structures by comparison with authentic synthetic compounds. 6. Confirm the biological activity of the synthesized compounds in both the laboratory and the field. This remains a generally sound protocol, but we recognized the serious deficiency of compromising on a laboratory instead of a field test to monitor the chemical fractionation. Field tests, we decided, would consume too much of the starting material and would take too much time. We were lucky; the laboratory response of walking insects led us to the compounds that evoked the aggregation response of flying insects in the field. In 1971, to reinforce point 6, I further made the deceptively simple statement that the synthesized and natural pheromone must have the same activity,2 but how to insure this was discreetly not specified. Also added was this statement: "Finally the entomologist must learn to use the synthetic material to manipulate the insect's behavior and to develop survey and control procedures. The hazards involved in such a study —— contamination