Occurrence Pattern And Selections Of Botanical Insecticides On The Striped Stem Borer, Chilo Suppressalis Occurred In Zizania Field

In this paper, the occurrence pattern of striped stem borer (SSB), Chillo suppressalis in Jiaobai, Zizania caduciflora field, the comparison between the rice SSB population and Zizania SSB population, the bioactivity on SSB of crude extracts of Ginkgo biloba leaf ,Oleander (Nerium indicum) leaf and Tripterygium wilfordii root bark all have been studied, and the efficacy of botanical insecticide on SSB in Zizania field was evaluated.The detailed results are shown as follows.This paper dealt with the overwintering, oviposition, boring and transferring behavior, population dynamics, and control of striped stem borer (SSB), Chilo suppressalis in Zizania fields. The results showed that SSB bored into Zizania stubble and overwinter in the form of 6th instar larva. Usually the peaks of pupation and eclosion were in April 15 to April 30 and April 20 to April 30, respectively. SSB female adults laid most of their eggs on the leaves, and less on the sheaths. Egg bulk was primarily distributed on the heart leaves, the first and the 2nd leaves. Newly hatched young larvae preferred to boring the inside of the 4th to 5th leaves , then transferred and bored into the sheaths of Zizania plants. The population of SSB in Zizania fields was very high and generations overlapped seriously. The peaks of egg hatching for the first, second and third generations of SSB in Jiaobai fields were from May 1 to May 20, July 5 to July 15, August 25 to September 5, respectively. Natural enemies of SSB in Jiaobai fields were mainly the larval parasitoid, Apanteles flavipes, and the fungi, Beauveria bassiana(Bals.).The over-wintered SSB, collected from rice fields initiated to emerge on April 20, nine days earlier than SSB collected from neighboring Zizania fields. The survival and pupation rates of over-wintered SSB collected from rice field were 67.30% and 70.06%, much higher than SSB collected from Zizania fields. The emerging rates were similar between SSB from both habitats, the sex ratios of SSB from rice and Zizania fields were 1:1.44 and 1:1 respectively. The preference test in laboratory showed that SSB from both rice and Zizania fields mostly prefered to oviposit on Zizania plants, however, the larvae chose to feed on rice plants. The field test indicated that SSB larvae hatched from Zizania plants could not transferred to rice fields due to the obstacle of field bund. The weight ofpupas and the size of SSB adults feeding on Zizania plants were significantly higher than SSB on rice plants, the esterase isozymes of SSB larvae collected from rice and Zizania habitats are obviously different. The inter-mating of SSB from two hosts could reproduce a significantly lower number of first progeny, indicating there are partially reproductive barrier of SSB from two habitats.Ginkgo biloba leaf crude extracts had a strong oviposition deterrent to SSB moth, 72 h after treatment with 1.25g/L, the deterrent rate reached 61.67%. In choice and non-choice tests, the medium antifeeding concentration (AFC50) of the extracts against SSB larvae in 2nd instar were 2.3g/L and 3.8g/L, respectively. The extracts also showed an obvious growth inhibition activity to the larvae. And the extracts presented some insecticidalactivity to the neonate of SSB.The bioassay of Oleander (Nerium indicum) leave crude extracts against SSB in field was studied, the extracts had an obvious systemic action, antifeedant and growth-inhibitory activity on SSB larvae. In free choice and no-choice tests, the medium antifeeding concentrations (AFCso) of the extracts to 2nd instar SSB larvae were 414.33μg/mL and 613.94μg/mL, respectively. The growth-inhibitory medium concentration was 1171.4μg/mL. In the systemic experiment, the extracts showed strong antifeedant and toxitic activities to SSB larvae. The extracts possesses low toxic activity to the neonate larvae and was safe for Apanteles flavipes adults, the parasitoid of SSB larvae.Tripterygium wilfordii root bark crude extracts had obvious stomach toxic, systemic action, antifeedent and growth inhibition ac...