Potential of Florida populations of Amblyseius largoensis (Acari: Phytoseiidae) as biological control agents of the invasive species Raoiella indica (Acari: Tenuipalpidae)

Abstract: Raoiella indica Hirst (Acari: Tenuipalpidae) is a phytophagous mite that recently invaded the Neotropical region. A predatory mite Amblyseius largoensis (Muma) (Acari: Phytoseiidae) has been found associated with R. indica in several areas recently invaded in the new world. A series of studies evaluated Florida (USA) populations of A. largoensis for potential control of R. indica by determining (1) the development and reproduction of A. largoensis feeding on R. indica and comparing its reproductive parameters to those obtained when feeding on other potential prey and pollen; (2) the prey-stage preferences of A. largoensis to R. indica; (3) the response of four populations of A. largoensis to R. indica and T. gloveri eggs and larvae; (4) the functional and numerical responses of A. largoensis to R. indica eggs, and (5) the effect of A. largoensis on R. indica densities using predator exclusion and predator release techniques. The results of these studies showed that (1) A. largoensis was able to feed, develop and reproduce on a diet consisting solely of R. indica showing improved reproductive parameters than when feeding on other prey and pollen; (2) A. largoensis showed preference for R. indica eggs followed by larvae, nymphs and adults; (3) the four populations of A. largoensis, all with different previous exposure to R. indica, were likely to accept and consume high numbers of R. indica eggs regardless of their previous feeding experience; however, A. largoensis showed plasticity in its response to R. indica larvae; (4) while feeding on R. indica eggs, A. largoensis females displayed a type II functional response with an increase in prey killed as prey density increased until a saturation level of approximately 45 R. indica eggs/day, a level at which oviposition by the predator was maximized (~ 2.36 A. largoensis eggs/day); (5) finally, a predator release rate of 1 A. largoensis female/ 10 R. indica adults reduced R. indica densities up to 50%. Overall, these results suggest that A. largoensis can play an important role in controlling R. indica populations in Florida.