A large patch of spider mites may be eliminated on one part of the plant, but another patch may go untouched. Egg dispersal is another significant factor. The protonymphs and deutonymphs of N. californicus are more active than those of N. fallacis . Predatory mites with larvae that feed more tend to grow into nymphs that feed less. These nymphs may be more specialized predators of spider mites.
Generalists are more common in subtropical tree crops and maintain themselves longer.
Using gereralist species may only require one release, whereas specialist species may require several releases. If the pest infestations are more dispersed, a generalist predator would be more effective. If the infestations are more aggregated, a specialist predator would be more effective. Depending on the type of infestation, one might want specialists or generalists or both. Responses to herbivore-induced plant volatiles Plants produce volatiles when under herbivore attack.