Researches On Developmental Characteristics Of The Pink Rice Borer, Sesamia Inferens, On Differernt Host Plants And Insecticides For Controlling The Borer

Sesamia inferens walker (Lepidoptera:Noctuidae) is one of the major pests to rice. It has a wide host range, so it is a typical of omnivorous insects. In recent years, for various reasons, S. inferens has significantly risen as a major pest in extensive areas where various crops including rice, special varieties of maize and vegetables are widely planted. This study is designed to aim at three aspects related to the upward population of S. inferens. First, to adapt to the market economy of our country in recent years, local cropping structure has changed greatly on a nation wide scale. Economic and forage crop planting area has been evidently increasing. In that S. inferens is one of polyphagous insects, the influence of different host plants to it has been unclear yet. So we need to study how the S. inferens larvae select different host plants and what its growing and developing characteristics are respectively after eating different host plants. Second, because effect of the currently and extensively used insecticides for control of S.inferens is not good, we need a screening in laboratory and further efficacy evaluation in field of distinct types of insecticides against the pest. Third, to meet the needs for green food and food safety, we need to exploit environment-friendly biocontrol agents by, first of all, collecting and isolating entomopathogenic resources from a disease or dead S. inferens in field, and identifying their insecticidal activity. The main results in this study are as follows.Newly hatched larvae of S. inferens to 7 kinds of host plants that are water bamboo (in market), wheat (Yangmai NO.8), corn (Jingtian NO.3, Jingnuo NO.3), rice (Nanjing NO. 11, Wuyujing NO.3, Liang-you-pei-jiu) showed significantly selectivity between a combination of two different host plants. And development and reproductivity of the S. inferens population varied significantly when it feeded on different kinds of host plants. Comprehensive evaluation using life table parameters showed that the most suitable plant for S. inferens development and reproduction is water bamboo, followed by Nanjing NO. 11, Liang-you-pei-jiu, Wuyujing NO.3, Jingtian NO.3, Jingnuo NO.3, and the wheat.Toxicity of several kinds of chemical insecticides to the eggs, first instar larvae, and third instar larvae of S. inferens was respectively determined in laboratory conditions. The results showed that the toxicity of avermectins, beta cypermethrin, emamectin benzoate (banleptm) and chlorantraniliprole to the S. inferens eggs,1 instar larvae, and 3rd instar larvae was evidently better than that of other tested insecticides. Found that the toxicity Cycloxaprid to the S. inferens eggs and 1 instar larvae was only less than the above four insecticides and LC was respectively 9.187 mg/L and 10.383 mg/L. The field test showed the similar results that efficacy of dosage 11.25 g (a.i.)/hm2 of emamectin benzoate 5% WG was 95.54% for control of S. inferens and 97.37% for control of damaged rice white heads (panicles), the best among those of the four tested insecticides in paddy, and efficacy of dosage 30 g (a.i.)/hm of chlorantraniliprole 20%SC was 89.61% for control of the borers and 95.33% for control of the rice white heads, much better than that of the control insecticide chlorpyrifos 40%EC at 480 g (a.i.)/hm2 or monosultap 92.1%T at 1200 g (a.i.)/hm. So emamectin benzoate or avermectins, and chlorantraniliprole were both kinds of insecticides more effective than the others for control of S. inferens in rice production.The microbes including 12 isolates of bacteria and 9 isolates of fungi were separated from disease-producing S. inferens worms. Of the microbes 5 isolates B11, B12, B22, B30 and B32, and one fungus F1 are evidently entomopathagenic to the 3rd instar lavae of Spodoptera exigua and Spodoptera litura in laboratory with the corrected mortality of 50% or more noctuids, And B30 virulence is the highest of the entomopathagens to the both noctuids respectively with the mortality of 92.9% against S. exigua and 79.4% against Spodoptera litura larvae just infected 5 days. The Fl pathogenicity to the 3rd instar larvae of S. exigua and S. litura was high respectively with LD of 5.0 x 10 and 2.65 x 105 spores per larva. And the corrected mortality of S. exigua and S. litura larvae feeding on diet including 5 X 106 F1 spores was respectively 100%和76.50%6 days.