MANIPULATING NATURAL ENEMIES BY PLANT VARIETY SELECTION AND MODIFICATION - A REALISTIC STRATEGY

The host plants of arthropod pests may affect parasitoids and predator s directly or indirectly, through multitrophic interactions. Direct pl ant effects may involve simple mechanisms such as reduced parasitoid s earching efficiency caused by trichomes. Multitrophic effects often in volve complex interactions that are not well understood, and their imp act on natural enemies and biological control are difficult to predict . Knowledge of the direct and multitrophic effects creates opportuniti es to increase the effectiveness of natural enemies by incorporating n atural enemy-enhancing traits into crop plants. The strategy may have potential for both generalist and specialist natural enemies, but the enemies' behavior and other factors will affect the results. Although combining natural enemies and plant resistance may slow the adaptation of some insect pests, it may speed up adaptations of others. A better understanding of plant/pest/natural enemy evolution is necessary to p redict how to combine natural enemies and plant resistance for the bes t long-term results.