| Following civilization more attation has been paid on products of natural plants which play a important role on encouraging studies of rencent to organic synthetical insecticides which is a serious threat to the environment such as resistance, residue and resurgence. In order to develop new ways for controlling the vegetable pests and providing possible the technical insectiside preperation joint-toxicity measurement of the extract collected by methyl alcohol from Sophora alopecuroides and seven alkaloids from the plant mixed with emamectin were carried out in this paper. In addition, experimental ecologic toxicology of the different mixtures insecticides to the larvae of diamondback moth Pullutella xylostella (L.)was studies in laboratory measurement including the toxicity variety under diffferent temperature or the different effectiveness of fecundity to the insect treated by sub-lethal dosage of the mixture were also surveyed, and the experimental population life tables of the mixtures were built in present paper.The results could be summarized as follows:1. The results of joint-toxicity measurement showed a obvious synergism after the combined application of the extracts from S. alopecuroides with emamectin. In the experipment we found that Aloperine and Sophoramin have stronger synergism action on emamectin than the other alkaloid. The synergistic ratio(SR) is 1.565 and 1.413. Sophoradine and Matrine have weakly synergism action on emamectin ,the SR is 1.013 and 1.138.Both the methanol extracts and water extracts have significant synergism action on emamectin which SR is 3.443 and 2.027.The synergisms of the two extracts are stronger than Sophoramin.2.The results of the toxicity of different mixtures insecticides to the diamondback moth Plutella xylostella in different temperature showed that the toxicities of the mixtures against the experimental insect were increased as the temperature enhanced in a limited temperature ranges. The topical toxicity of emamectin increased by 14 folds as the temperature changed from 16 to 31℃; however, 11 folds and 25 folds bioeffect was achieved for the two compound mixtures when the temperature was enhanced from 16 to 31℃. Meanwhile, the contact poisoning effect showed that the toxicity of the two compound mixtures were much higher than emamectin.3. The bioeffects of different mixtures insecticides were investigated in present paper which including oral toxicity determination and the odditional effect under the sub-lethal dose of the tested insecticides and the results showed that the oral toxicity of mixture compounds to the larvae of Plutella xylostella were much highter than emamectin compound. The lethal concentration (LC50) of the mixtures and emamectin to the tested insect were 0.1437 mg/L, 0.2441mg/L and 0.4947 mg/L respectively. The pupated percentage, emergence percentage and fecundity of Plutella xylotella were affected obviously after treated by sub-lethal dosage of the insecticide mixtures. Meamwhile, the effects on the oviposition and egg hatch of Plutella Xylostella were investigated after treated by sub-lethal dosage of the compound mixtures. the average egg number laid were 118.87±34.09,124.26±46.88 and 133.03±23.18 respectively, while that for the control group was 187.70±53.35. The hatching rate of the eggs laid by the Plutella Xylostella were decreased to 52.25%, 53.25%and 59.00%, However , that of eggs laid by the control Plutella Xylostella was 82.50%.4.The results of the second-generation life tables of Plutella xylostella after treated by sub-lethal dosages of different mixtures insecticides showed that these of all the three compounds or mixtures affected the experimental insect obviously. The life tables were constructed after treated by the insecticides and the average values of demographic constants were determined as follows: The index of population trend were lower compared with the control population which were 6.23, 4.81 and 5.70 for three mixtures than the value 28.03 for the control . |
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