Combined effects of the entomopathogenic fungus, Paecilomyces fumosoroseus Apopka-97, and the generalist predator, Dicyphus hesperus, on whitefly populations

The effects of intraguild interactions between Dicyphus hesperus Knight (Hemiptera: Miridae) and Paecilomyces fumosoroseus Apopka-97 (PFR-97 (TM)) (Wize) Brown and Smith (Ascomycota: Hypocreales) on Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) populations were investigated in tomato greenhouse microcosms. Conditions were established in which interference or synergy would most likely occur; namely, a high number of available whiteflies were combined with large numbers of both D. hesperus and PFR-97 (TM). We measured live whitefly density in a factorial repeated measures experiment where plants were provided or withheld releases of D. hesperus and/or applications of PFR-97 (TM) for 6 weeks. Releases of D. hesperus were made at a rate of 10 adults/plant during the first and third week and PFR-97 (TM) suspensions were applied with a backpack sprayer at a rate of 18 x 10(7), 1.3 x 10(7) and 1.2 x 10(7) viable blastospores/ml during the first, third and fourth week, respectively. Results revealed a non-significant interaction effect between D. hesperus and PFR-97 (TM), indicating that their actions were independent. Individual whitefly reductions of 48% and 35% were achieved by PFR-97 (TM) and D. hesperus, respectively. Collectively, the natural enemies reduced whitefly densities by 62% relative to the controls. The density of D. hesperus adults was unaffected by multiple applications of PFR-97 (TM). These results suggest that the combination of generalist entomopathogenic fungi and generalist predators has the potential to cause increased pest mortality despite evidence of minimal interference.