Suitability of pollen as an alternative food source for different developmental stages of Amblyseius herbicolus (Chant) (Acari: Phytoseiidae) to facilitate predation on whitefly eggs

Abstract

Alternative food sources could sustain predator populations by influencing their perfor¬mances including predation, development, and reproduction in periods of shortage or scarcity of prey under laboratory or fields conditions. The aim of this study was to explore suitability of cattail pollen (Typha orientalis) as an alternative food source for different stages of Amblyseius herbicolus (Chant) (Acari: Phytoseiidae) on their predation capacity against the eggs of whitefly Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyro- didae), and the developmental and reproductive responses of the predators to different diet switching regimes under laboratory conditions (T1: Nymphs and early adults fed pollen; T2: Nymphs fed pollen but early adults fed whitefly eggs; T3: Nymphs fed whitefly eggs but early adults fed pollen; T4: Nymphs and early adults fed whitefly eggs). Results in the diet switching experiment revealed that although A. herbicolus could prey on whitefly eggs in all the treatment groups, the predatory mites obviously differed in their capacity to prey on the target pest whitefly eggs when fed on cattail pollen and whitefly eggs during different developmental stages. A. herbicolus in group T2 revealed the highest average predation rate, being 1.31, 1.17, and 1.49 times those in groups T1, T3, and T4, respec-tively. Our results indicated that food sources including cattail pollen and whitefly eggs were suitable for A. herbicolus, because it was able to develop from egg to adult females in all the treatment groups. The mixed diets (T2 and T3 groups) revealed positive effects on the developmental and reproductive parameters of A. herbicolus females, leading to higher oviposition rates and shorter developmental durations when compared with those of groups T1 and T4. A. herbicolus in group T2 revealed the highest average oviposition rates (1.32, 1.26, and 1.81 times those in groups T1, T3 and T4, respectively); however, no significant differences were observed between the T1 and T3 groups. All the eggs of A. herbicolus succeeded in reaching adulthood, but the duration of egg to adult developmental time of A. herbicolus was different among the four treatment groups. The longest and shortest developmental times were obtained in groups T4 and T3, respectively. All the results in the present study demonstrated that A. herbicolus adult females can prey on T vaporariorum eggs, and cattail pollen was suitable as an alternative or additional food source with high nutritional value for this predatory mite to enhance the predation capacity towards whitefly eggs because A. herbicolus can successfully complete its immature development as well as reproduction.