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 effectiveness of natural enemies in maintaining low densities of the pink pineapple mealybug, Dysmicoccus brevipes (Cockerell), in pineapple plantings in Hawaii. In the biological check method, the treatments were ant-free plots and ant-infested plots. The numbers of D. brevipes, parasitized mealybugs, and immature and adult predators on the aerial parts of the plants were recorded. Results in the biological check method suggested that Anagyrus ananatis Gahan was responsible for the decline of D. brevipes densities in the absence 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 natural enemies, natural enemies but no ants, and ants and natural enemies, This experiment showed that in the absence of the big-headed ant, Pheidole megacephala (F.), D. brevipes densities were greatly reduced by natural enemies and probably by the lack of sanitation or other ant activity, A laboratory study also was conducted to evaluate the impact of P. megacephala on oviposition and predation by A. ananatis and the coccinellid Nephus bilucernarius Mulsant, respectively. These laboratory studies indicated that P. megacephala significantly decreased mealybug mortality induced by A. ananatis and N. bilucernarius adults via interference with natural enemy searching behavior. (C) 1999 Academic Press.