Fitness Evaluation Of Trialeurodes Ricini(misra) As The Alternative Host In A Banker Plant System

Trialeurodes vaporariorum and Bemisia tabaci are two notorious pests in greenhouse producing vegetables. Widespread using of pesticide not only have lead the resistance of target pests, but also the residue in products and threaten the healthy of people. Biological control was the most effective tool in the pest-management arena, and the banker plant system was a new concept of biological control. The system can maintain the population of natural enemies by itself, and make up the short validity and the high cost that happened in the tranditional bio-control methods.Encarsia formosa, a successful commercial natural enemy, that was widely used for controlling whiteflies. On the base of establishing the ‘Casor- Trialeurodes ricini –Encarsia formosa', we evaluated the applicability of T. ricini as the alternative host in this system.(1) Using the choice and no-choice tests of Trialeurodes vaporariorum and Bemisia tabaci between vegetable plants(tomato, cucumber, eggplant, beans and sweet pepper) and castor to evaluate the castor. The choice tests results showed that the preference of the two whitefly species on castor was lower than vegetables. The no-choice tests showed the similar results, the landing number of whiteflies on castor were significantly lower than vegetable plants after 72 h, it meaned the survivorship of T. vaporariorum and B. tabaci were very low. So we spectulated the castor was suitable as the banker plant.(2) For evaluating the T. ricini, we tested the choice and no-choice of T. ricini between vegetable plants and castor, the number of eggs, survivorship of T. ricini nymphs on 12 plants. The no-choice tests told us no live T. ricini adults on cucumber and sweet pepper after 12 h, and its survivorship on tomato and beans was lower than 2% after 24 h. The choice tests showed T. ricini would not land on vegetables when castor plants co-existing.The number of eggs of 20 adults in 48 h was highest on castor, intermediate on eggplant beans, cotton and sweet potato(16-36), lowest on tomato, cabbage, cucumber, sweet pepper,pepper and melon(lower than 4). And few T.ricini adults emerged from sweet pepper,tomato, cabbage, cucumber, pepper, melon and sweet potato.(3) Encarsia formosa reared from T. vaporariorum preferred feeding on the first instar nymphs and ovipositing in the first and fourth instar nymphs of T. ricini. The second instarwas the least favorite instar for parasitizing. E. formosa can successfully finish its development whichever nymphs instar was parasitized.(4) We tested the parasitism, emergence rate, weight and development of E. formosa reared from three whitefly species(T. vaporariorum, T. ricini and B. tabaci) on tomato,cucumber and bean plants infested by T. vaporariorum and B. tabaci. The results showed Ef-Tr(E. formosa reared from T. ricini) can parasitize the nymphs of two whitefly pests on three vegetables and successfully finish its development. The parasitism of Ef-Tr to T.vaporariorum on three plants were higher than 50% and the emergence rate of offsprings higher than 85%. The weight of offsprings on tomato and cucumber were as high as Ef-Tv(E. formosa reared from T. vaporariorum), and we speculated the offsprings has the higher egg-loading number, longer life and higher parasitism. The weights were lower and the development time of offsprings were longer when Ef-Tr parasitizing B. tabaci on three vegetable plants, but the parasitism could reach to 45%. So we assumed ‘Castor- T. ricini-E. formosa' banker plant system could be used for controlling T. vaporariorum and B.tabaci in greenhouses.(5) The functional response, searching efficiency and intra-species disturbance of Ef-Tr were used to caculate the maximum parasitized number of T. vaporariorum and B. tabaci nymphs on tomato. The results showed that the instant attack rate(a) of Ef-Tr to T.vaporariorum and B. tabaci were 1.04 and 0.92, respectively. And the maximum parasitized nymphs number were 29.9 and 25.4, respectively. The searching effciency of Ef-Tr decreased with the host density, and the parasitism of per wasps was decreased with the density of itself.(6) The olfactory response of E. formsa to volatiles from tomato plant, honeydew or empty pupal cases(EPC) of whiteflies were tesed using a Y-shape olfactometer. E. formosa showed positive trends to honeydew produced by nymphs of three whitefly species, and to EPC of whiteflies but not the EPC of itself. The trends of E. formosa between healthy tomato and clean air was not obvious. They perferred the clean air when damaged leaves or leaves infested by nymphs were provided with the clean air. However, when different treatment leaves were simultaneously provided and any two of them as the odor source at the end of two arms of Y-olfactometer, E. formosa tended to choose the leaves were damaged or infested by B. tabaci.In conclusion, castor and T. ricini were optimal as the banker plant and alternative host respectively in a banker plant system to rear E. formosa. And the parasitoid reared from T.ricini can oviposit in T. vaporariorum and B. tabaci on three vegetable plants, and can successfully finish its development. So this system is technically possible. E. formosashowed positive trends to volatiles from infested-plants and kairomone(honeydew and EPC,the empty pupal cases), so we can use this materials to regulated the behavior of parasitoid,and enhance the controlling effciency of natural enemies.