Effect Of Pyriproxyfen On Eggs, Larvae, Pupae And Adults Of Serangium Japonicum, A Predator Of Bemisia Tabaci

Serangium japonicum (Chapin) is a regnant predator of Bemisia tabaci (Gennadius), andthe adult of S. japonicum could eat more than700eggs of the B. tabaci in one day.Pyriproxyfen was a juvenile hormone analogue with many advantages, such as low toxicity tomammal, friendly to environment. In this research, we evaluated the effects of pyriproxyfenon the eggs, larvae, pupae and adults of S. japonicum to explore the compatibility betweenpyriproxyfen and S. japonicum. The treatments included200mg [AI]/L and100mg [AI]/Lpyriproxyfen and two controls: solvent control and water control (distilled water was used).All the compare were based on solvent, and if differences existed between solvent control andwater control, there would be a statement. The main findings are shown as follows:(1) Eggs of S. japonicum were directly dipped into pyriproxyfen treatments or control.The S. japonicum eggs stage was sensitive to the pyriproxyfen, while the larval hatching ratedecreased to20.0%and3.3%respectively when the eggs were dipped into200mg [AI]/Land100mg [AI]/L of pyriproxyfen. There were significant difference in larval hatching ratesbetween solvent control and the treatment of pyriproxyfen at200mg [AI]/L.(2) All larval stages of S. japonicum successfully developed to adult stage when they atetreated B. tabaci eggs by pyriproxyfen. Eclosion rate of S. japonicum adults significantlydecreased by40%when second instars started eating the treated B. tabaci eggs (200mg[AI]/L). The developmental time of fourth instar was prolonged among the larva treatedbegin with second or third instars on the concentration of200mg [AI]/L. With theconcentration of100mg [AI]/L pyriproxyfen, the total developmental time from treated instarto adult was significantly different. Being treated from third instars, the total time wasprolonged while the results were opposite if treated from the fourth instar larvae.(3) S. japonicum pupae were dipped into pyriproxyfen solution or control solvent as thetreated method in eggs stage. Emergence rate of the adults didn’t significantly decreased aftertreated by pyriproxyfen, and the numbers were94.6%,93.3%and83.8%respectively whentreated by solvent control,100mg [AI]/L and200mg [AI]/L pyriproxyfen.(4) The adults also were treated by feeding treated B. tabaci nymph. When the S. japonicum adult fed on B. tabaci nymph treated with100mg [AI]/L pyriproxyfen, one femaleproduced8.0eggs per day, while the number in control group was2.5; and then the hatchingrate of these eggs decreased by55.9%.On conclusion, larvae and pupae of S. japonicum were not very sensitive to thepyriproxyfen, as long as within the recommended dose (100mg [AI]/L). However, we needavoid applying pyiproxyfen during the hatching period of S. japonicum, which could be abouttwenty days after releasing, the used of pyriproxyfen would therefore not jeopardize S.japonicum population.