Direct and Indirect Effects of Plants on Performance of Beneficial Organisms
Biological pest control has experienced a revival in the past decades, and its role in pest control is still increasing both in greenhouse crops and in field crops [33,78,125,129,235]. In many instances, the direct financial stimulus for utilization of biological control [124,126,129] has been combined with political measures that stimulate biological control while discouraging the application of synthetic pesticides . This development has been a significant impetus for the use of both biological control and host plant resistance practices. In effect, the two pest control methods have been or will often be integrated. However, it is not a priori obvious that these two strategies are synergistic. Plant characteristics not only affect herbivores but they may affect the plant-inhabiting or visiting natural enemies of herbivores too. This latter aspect has often been neglected, but in the past 15 years, it has become better documented that plant characteristics may decisively affect carnivore performance in many respects [e.g. 20,26,45,50,96,97,127,128,175,229]. Therefore, changes in plant characteristics through breeding for resistance to herbivores is likely to result in changes in the way plants affect the natural enemies. Thus, it is essential to analyze plant-herbivore-natural enemy interactions for crop protection programs in which both host plant resistance and biological control are important components of pest control either intentionally or passively. Otherwise, plant breeding programs may result in a pest control program that is less rather than more effective.