Studies On Biology Characteristics And Biological Control Of The Rice Stem Borer Chilo Suppressalis In Heilongjiang Province

In this paper, the biology characteristics and life cycle of rice stem borer Chilo suppressalis (Walker) (Lepidoptera:Pyraridae ) in Heilongjiang province are systematicly studied. The host plants and thermal constants were also studied. The assessment of output loss was given in different density of rice stem borer,and the method of biological contol was inquired into at the same time.The research result shows: The rice stem borers lived as mature larvae in the stems and stubbles of rice and barnyard grass in winter in HeiLongjiang province, Chilo suppressalis occurred one generation each year. The overwintering larvae startled pupating in the last ten days of May, went to peak from the first ten-day to the middle ten-day of June, and get down the last ten-day of June. The average of pupal period was 10.9 d. The initial stage of the adult worm emergence was hi the beginning of June, the peak period was in the second and third ten days of June, ending in the beginning of July. The average time from adult worm emergence to oviposition was 5.5 d. The adult stage was about 6.5 d. The adult preoviposition was in the first ten days of June, and the peak period was from the end of middle ten days to the last ten days of June. The last oviposition stage was in the beginning of July, and the oviposition period was about 7d. The initial stage of hatching period was in the middle of June. The peak period was from the last of ten days of June to the first ten days of July. The larvae did not injure the rice until the majority of mature larvae in the stem and stubble in the middle and the last of September for overwintering.The host plants of rice stem borer were investigated. It was proved that the rice stem borer did harm to the grass such as rice,wheat,corn millet and Chinese sorghum and it showed the typical damaged symptom. The adults had obvious phototaxis.They mainly massive ovipositted in the back basilaminar of blades near the sheath, and the front of blades near the leaf apex. There was host selectivity when they ovipositted. They prefered to oviposit in the dark green, thick and exuberant plant. They ovipositted the most quantity at rice, more at corn, Chinese sorghum,millet and wheat, seldom at barnyard grass. The hatched larvae resembled together at the sheath and made it scorched. The larvae scattered to the other plants after 2 to 3 larval instar resulting in deathheart, deathbooting and wite stachys. The larvae were water-tolerant and heteroicous.The development lower thresholds and thermal constants were 11.9+1.1 and 121.8+ 1.8day-degrees(dd);18.5+0.9 and 37.1+0.9 dd;14.2+2.5 and 55.0+1.5 dd;15.7+1 and 45.3+2.3 dd;13.0+1.9 and 66.1+1.5 dd;10.1+0.5 and 84.3 +2.8 dd;14.9+1.2 and 62.6+2.1 dd;17.0+3.4 and 73.3+0.9 dd,for overwintering pupae, adults of male and female without feeding syrup, egg, 1st-5th larve instars, respectively.The mixture of Bt and biological pesticide took great effects on controlling the rice stem borer.The mortality were 78.1% and 100% after treating with the mixture 24h and 48h later respectively.The main factors for decreasing output were deathheart and wite stachys. The attacked plants had more effects to the output loss also. The output loss were 33.39%, 34.66%, 38.36% and 50.64% larvae per plant at 8, 10 , 14 and 20.Candidate: Pei Halving Speciality: Agricultural Entomology & pest controlSupervisor: Prof. Zhao Kuijun...