entomologists have concluded that introduced biocontrol agents are most effective when they exhibit the following characteristics:

Narrow host range. Generalized predators may be good natural enemies but they don't kill enough pests when other types of prey are also available.
Climatic adaptability. Natural enemies must be able to survive the extremes of temperature and humidity that they will encounter in the new habitat.
Synchrony with host (prey) life cycle. The predator or parasite should be present when the pest first emerges or appears.
High reproductive potential. Good biocontrol agents produce large numbers of offspring. Ideally, a parasite completes more than one generation during each generation of the pest.
Efficient search ability. In order to survive, effective natural enemies must be able to locate their host or prey even when it is scarce. In general, better search ability results in lower pest population densities.
Short handling time. Natural enemies that consume prey rapidly or lay eggs quickly have more time to locate and attack other members of the pest population. Small populations of efficient natural enemies may be more effective biocontrol agents than larger populations of less efficient species.
Survival at low host (prey) density. If a natural enemy is too efficient, it may eliminate its own food supply and then starve to death. The most effective biocontrol agents reduce a pest population below its economic threshold and then maintain it at this lower equilibrium level