Pest Control: from Chemical Ecology to Evolution. A Hungarian Perspective

From 1880, the year of funding the National Phylloxera Research Station, the predecessor of the present Department of Zoology of the Plant Protection Institute, the main thrust of entomological research was towards solving practical problems in agriculture, which mission governs our recent activity and guides our plans for the future. Our studies on the behaviour of herbivorous insects have shown that oligophagy is mainly due to the sensitivity of the insects' chemosensory system to deterrent chemicals occurring in the non-host plants. This enables the use of antifeedants in pest control. In field experiments the insects found their hosts largely by chance, which has implications for crop rotation. The ability of learning in some herbivorous insect species has been demonstrated. It may result in induced preference for some otherwise avoided plants. Ecological studies indicated that predispersal seed predators do not necessarily affect plant population dynamics and that there is no interspecific competition among them. Studying the presumable processes that drive the evolution of insect-plant associations resulted in elaborating the theory of sequential evolution instead of the theory of coevolution. In course of 30 year studies, female-produced sex pheromones were evidenced in behavioural studies, isolated, and chemically identified in cooperations with organic chemical laboratories, for a few dozens of lepidopterous species. Related sex attractants were established by means of field trappings for further dozens of species. Based on these results, the role of sex pheromones in maintaining reproductive isolation between taxonomically closely related, sympatric species, as well as the chemotaxonomical value of sex attractants in higher taxa of Lepidoptera are discussed. As a result of our studies on Elateridae (Coleoptera) we developed and optimized pheromone baits and traps for catching males of all important pest Agriotes click beetles in Central and Western Europe. The most effective pheromone combinations for each species were tested in a Europe-wide comparative effort, giving information on the probable importance of the respective species in the respective area. In Scarabaeidae (Coleoptera) we discovered sex attractants for 3 species of the genus Anomala, and floral attractants for 4 species of the subfamily Cetoniinae, all orchard pests damaging fruits or flowers. Traps were developed for these scarabs taking into consideration the optimal visual and chemical cues for each respective species. The trap and bait combinations show preliminary evidence that their use for direct control through mass trapping is possible. Among chrysomelid beetles, new trap types were developed for the western corn rootworm Diabrotica v. virgifera. These trap types are widely used in Europe for the detection and monitoring of the pest. Most recent results concern the relationships between host-plant related and pheromonal communication in flea beetles (Phyllotreta spp.).