| Rice stem borer (Chilo suppressalis Walker) is one of the main rice pests in Asia. It is always difficult to control for features of rilling decayed hazard. In recent years, with the large-scale use of chemical insecticide, both the occurrence and development of resistance of Chilo suppressalis to chemical insecticide are enhanced, which increase the difficulty of prevention. So it is signality for the task of resistance management to carry out resistance monitoring, biochemical resistance mechanism and new pesticide development.Based on the resistance monitoring of Chilo suppressalis with several kinds of common insecticides in six counties of Sichuan province between 2008 and 2009, we studied the resistant mechanism among field populations and screen for higher biological activity and different mechanisms to formulate. Meanwhile, we also involved the study on effervescent tablet, considering the ecology system. The results explicited the resistant situation, physiological and biochemical resistant mechanism among field populations. These data also provided important reference on understanding of the resistant level and the resistant management in different geographic populations in China. The main results were as follows:1. Resistance monitoring of Chilo suppressalisMicro-drop method was used to monitor the susceptibility of Chilo suppressalis to monosultap, triazophos, chlorpyrifos, Dipterex, fipronil, Avermectins, emamectin benzoate, collected in Nanbu, Yucheng, Pengshan, Shuangliu, Lezhi and Qionglai, respectively. The results showed as follows:①Populations of Chilo suppressalis in Sichuan province produced medium to high level resistance to monosultap, triazophos, chlorpyrifos. Through the resistance monitoring results, we could see a clearly resistance growth. The resistance ratio in Shuangliu witnessed a significant growth, from 43.4981 in 2008 to 93.7325 in 2009. The pest resistances multiples growth to monosultap was flat in the six regions, only Qionglai increased 17.5181 times. The resistance ratio to chlorpyrifos increased fast only in Pengshan and Shuangliu,14.0251 and 23.0121 times, respectively.②Populations of Chilo suppressalis in Sichuan province produced in sensitivity to decreasing or medium resistance level from 2008 to 2009 in the six regions. Compared to triazophos, the pest resistances multiples growth to Dipterex was gradual in the six regions. Yucheng and Lezhi increased 1.3591 and 1.7558 times respectively. Nanbu, Pengshan, Shuangliu and Qionglai decreased 2.3004,2.1328,1.1929 and 0.2349 times, respectively.③The resistance of Chilo suppressalis field populations in six regions to fipronil, abamectins and emamectin benzoate was relatively low. Emamectin benzoate had higher activity:LD50=0.00022～0.000535ng/larva in 2009. Through resistance monitoring results between 2008 and 2009, it showed a slowly rising trend to the three reagents mentioned above. Fipronil, which has been banned to use for rice growth, remained showing high biological activity. The resistance of Chilo suppressali to Abamectins and Emamectin benzoate was much slower than other pesticides. The fastest growing resistance to abamectins was the Shuangliu population,2.479 times from 2008 to 2009. The slowest one was the resistance to Emamectin benzoate:the fastest growth field was Qionglai population, which only 0.5172 times.2. Biochemical mechanism of resistance of Chilo suppressalis field populationsThe research materials were from resistance population and indoor sensitive strain.①We tested the activity of CarE, ACP, ALP, AchE, GSTs, MFO, Proteinase, POD, SOD, CAT and the content of FAT in different strains. The results showed that each enzyme and crude fat content were significant different existing in the field resistance population and indoor sensitive, which might mean that it had some connect with resistant mechanism;②Comparing various enzymes activity with insect resistance level of monosultap, triazophos, fipronil, emamectin benzoate (LD50) correlation analysis, we learned that there were significant correlation between the resistance and the biology activity of AchE, GSTs, MFO, SOD, CAT. GSTs's activity and insect resistance to triazophos had significant correlation (r=0.86*); MFO's activity and insect resistance to fipronil had significant correlation (r=0.74*); AchE activity and resistanceof Chilo suppressalis to monosultap, triazophos, fipronil, emamectin benzoate were obvious negative correlation, related coefficient was -0.86**,-0.79*,-0.60,-0.55; SOD activity and resistance of Chilo suppressalis to emamectin benzoate had significant correlation (r=0.71). CAT activity and resistance of Chilo suppressalis to monosultap had significant correlation (r=0.78*).3. Study on formulation-effervescent tablet Based on the resistance monitoring and resistance mechanism, emamectin benzoate and monosultap were chosen for formulation and processing, which were in two different mechanism and no cross-resistance, The results were as follows:①Emamectin benzoat and monosultap mixed significant synergistic effect, and had a wide spectrum of the effective ratio. LD50 of emamectin benzoate was 0.5964ng/larva and the LD50 of monosultap was 21501ng/larva. The difference of the virulence between them was 36051.31 times. The research of co-toxicity coefficient showed that the ratio among 1:1000～1:36051 had significantl synergy effect.②The results of effervescent tablet test showed that the best recipe was:emamectin benzoate,0.04%; monosultap:39.96%; dispersant NNO,3%; Wetting agent:Tween-80,2%; Binder:polyethylene glycol 6000,3 %; Disintegrating agent:sodium bicarbonate+citric acid (1:1),40%; Packing:lactose+ sodium(1:1),12%.③Compared with single agent of emamectin benzoat and monosultap, its chemical toxic effect was more remarkable. For the preparation in the LD50 (ng/larva), the insecticidal effect of emamectin benzoate and monosultap effervescent tablet was (LD50≈335ng/larva) more significant than market 3.6% monosultap big granule (LD50=2714ng/larva). Due to the little proportion of emamectin benzoate in this tablet, when compared with the 0.2% emamectin benzoate soluble powder in LD50, the usage rate on emamectin benzoate between them was about(0.335:13.71)1:41, So it could greatly reduce the use of emamectin benzoate.
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