Natural enemies can be released into a crop one species at a time, or mixed with other beneficials. Natural enemy compatibility may be a concern when several species are commercially available for inundative biological control. Many natural enemies are quite capable of consuming other beneficials that they encounter. The net effects of these potentially harmful interactions on the pest population are largely unknown. Although compatibility of parasitoids and predators has been reported for silverleaf whitefly, relative effectiveness of releasing single or multiple species has only recently been studied.
Three silverleaf whitefly natural enemies, with potentially negative interactions, were released alone or in combination. Two were the wasps Encarsia formosa and E. pergandiella. When these parasites lay eggs into 3rd and 4th instar whitefly, the immature parasites develop into females. To produce males, however, female parasites act as a hyperparasite. They lay eggs into whiteflies that have been previously parasitized by the same or other parasite species. The third species in this study, Delphastus pusillus, is a lady beetle with a voracious appetite that can consume immature parasitoids but not pupae or adults.
Simultaneous release of all three species provided as good or better whitefly suppression than releasing any of the individual species alone. Releasing two species provided better suppression than at least one of the two species released. The natural enemy composition influenced the level of control more than the number of species released. The greatest levels of suppression occurred when D. pusillus was released alone or in combination with one or more of the other species. Releasing E. formosa with E. pergandiella in combination provided better control than either of the two species alone but was not as effective as the D. pusillus treatments.
Return to Commodity Menu Vol. III No. 10
Return to Contents Menu Vol. III No. 10 Go To Index