Boletín de la AeE

Agricultura! ecosystems are characterized by a complex network of interactions. Three operational groups of natural resources determine the regulation of pest populations: Natural antagonists. plants and plant communities. and biological control agents. These operational factors are all interrelated and thus subject to dynarnic change. All of the factors, as well as their interrelationships, are potential targets for anthropogenic influence on pest populations.

Investigations on the influence of plants and plant communities provide information for the design of a suitable habitat. This is exemplifíed by a study on chemically-mediated interactions between parasitoids and cassava. The specialist Aenasius vexam is attracted by mealybug-infested plants in the y-tube olfactometer, the generalist Acerophagus coccois simply by cassava plants, irrespective of their status of infestations. Implications of the different foraging strategies for diversifíed agroecosystems will be discussed.

Investigations focusing on natural encimes and their communication with herbivorous hosts contribute to a better understanding and a realistic judgement on strengths and limits of the effkacy of antagonists. This will be substanciated starting from vibratory-mediated interactions between Sympiesis sericeicornis and apple leaf miners: A parasitoid using the host vibrations for its localisation may be more successful when the hosts occur at low densities. i.e. when the number of possible vibrational sources per leaf is limited.

Investigations centering around biological tools as insect control agents could open up new perspectives for mass rearing and mass releases. Knowledge of relevant stimuli for host location - visual, chemical. vibrational - could be used to optimize mass rearing as well as foraging success in the reléase phase of parasitoids. An approach to exploit vibrational cues for the host-free mass rearing of an ectoparasitoid will be developed,