Impact of Pheidole megacephala (F.) (Hymenoptera : Formicidae) on the biological control of Dysmicoccus brevipes (Cockerell) (Homoptera : Pseudococcidae)

Two held experiments designed as the biological check method (interference) and the paired-cage technique (exclusion) were used to evaluate the effect iveness of natural enemies in maintaining low densities of the pink pineapp le mealybug, Dysmicoccus brevipes (Cockerell), in pineapple plantings in Ha waii. In the biological check method, the treatments were ant-free plots an d ant-infested plots. The numbers of D. brevipes, parasitized mealybugs, an d immature and adult predators on the aerial parts of the plants were recor ded. Results in the biological check method suggested that Anagyrus ananati s Gahan was responsible for the decline of D. brevipes densities in the abs ence of ants. In a second study combining the paired-cage technique and the biological check method, the treatments included mealybug-infested potted pineapple plants with no ants or mealybug natural enemies, ants but no natu ral enemies, natural enemies but no ants, and ants and natural enemies, Thi s experiment showed that in the absence of the big-headed ant, Pheidole meg acephala (F.), D. brevipes densities were greatly reduced by natural enemie s and probably by the lack of sanitation or other ant activity, A laborator y study also was conducted to evaluate the impact of P. megacephala on ovip osition and predation by A. ananatis and the coccinellid Nephus bilucernari us Mulsant, respectively. These laboratory studies indicated that P. megace phala significantly decreased mealybug mortality induced by A. ananatis and N. bilucernarius adults via interference with natural enemy searching beha vior. (C) 1999 Academic Press.