Biological characteristics, functional and numerical responses of the predatory mite Amblyseius swirskii feeding on cotton whitefly, Bemisia tabaci

Amblyseius swirskii Athias-Henriot has attracted substantial attention as a biological control agent. The life history traits, and functional and numerical responses of A. swirskii fed on Bemisia tabaci (Gennadius) was studied under laboratory conditions (25±1°C, 60±5% RH and 16 L: 8D). Predatory mite was able to feed and complete its development on both B. tabaci eggs and 1st instar nymphs. Total preadult developmental period of female A. swirskii fed on eggs and 1st instar nymphs of B. tabaci were 5.62 and 5.12 days, respectively. Sex ratio (female percentage) of A. swirskii feeding on above diets were 70 and 72 %, respectively. Female longevity of A. swirskii fed on above mentioned diets were 25.27 and 26.97 days, respectively, and total fecundity were 47.20 and 41.70 eggs, respectively. Intrinsic rate of increase (rm) of A. swirskii fed on above mentioned diets were 0.2040 and 0.1863 day-1, respectively. A type II functional response for feeding A. swirski on different densities (5, 10, 20, 30, 45, and 60) of B. tabaci eggs was determined. The highest mean number of preys fed by a single female A. swirskii were 38.50 and 34.70 eggs which were recorded at densities of 60 and 45 preys, respectively, with no significant difference. Searching efficiency (a) and handling times (Th) of the female mites were estimated as 0.1056 h-1 and 0.3534 h, according to nonlinear least-square regression. The maximum theoretical predations (T/Th) for female mites was 67.91 eggs/day. The reproductive numerical response, in terms of eggs laid, showed no significant difference with increasing prey density. There was also no significant difference between longevity of female mite in different densities of B. tabaci eggs. Overall, the results of the present study indicated that A. swirskii has a good potential to control B. tabaci. Therefore, further glasshouse and field research is warranted.