几种药剂对桃蚜和两种瓢虫的毒力选择性研究

在室内分别测定了吡虫啉，吡虫啉＋增效剂，氰戊菊酯，硫丹、乐果和灭多威6种杀虫剂对桃蚜Myzus persicae Sulzer，七星瓢虫Coccinella septempunctata Linnaeus和龟纹瓢虫Propylea japonica(Thunbery)的毒力，比较了药剂在桃蚜和两种瓢虫之间的选择毒力比值（STR），以及药剂之间选择性差异，研究了桃蚜对不同药剂相对适合度，结果表明：吡虫啉＋增效剂（SVI）和吡虫啉对桃蚜的毒力均很高，LC50分别是4628mg/L和0．9535mg/L，吡虫啉在七星瓢虫和桃蚜之间，龟纹瓢虫和桃蚜之间的STR值分别是37．6和13．0，吡虫啉＋增效剂的STR分别是9．84和7．75，硫丹的SR分别是54．0和7．28，都表现出显的毒力选择性，而氰戊菊酯，乐果和灭多威的STR值均很小（0．02－0．21），不仅对桃蚜毒力低，而且对两种瓢虫也不安全，用吡虫啉和吡虫啉＋SV1的LC50浓度处理桃蚜，其存活个体的产仔率和单雌产仔量明显减少，与其它药剂处理相比，显降低了桃蚜的相对适合度，六种杀虫剂处理的桃蚜种群，其相对适合度大小排列为：乐果EC（0．92）＞氰戊菊酯EC（0．67）＞灭多威EC（0．66）＞硫丹EC（0．51）＞吡虫啉WP（0．40）＞吡虫啉＋增效剂（SV1）EC（0．18），由此证明，吡虫啉不仅对桃蚜毒力高，对天敌瓢虫杀伤力小，而且对桃蚜种群有持续控制作用。

STUDIES ON SELECTIVE TOXICITY OF SIX INSECTICIDES BETWEEN GREEN PEACH APHID AND LADYBIRDS

The selective toxicity of six kinds of insecticides, including imidacloprid, imidacloprid+synergist (SV1), fenvalerate, endosulfan, methomyl and dimethoate, between the green peach aphid (Myzus persicae Sulzer) and two species of ladybirds (Coccinella septempunctata Linnaeus and Propylaea japonica Thunbery), was investigated in the laboratory. The results showed that both imidacloprid WP and imidacloprid+synergist (SV1) EC possessed the highest toxicity to the aphids. Between C. septempunctata and M. persicae and between P. japonica and M. persicae, the selective toxicity ratios (STRs) of imidacloprid WP, imidacloprid+ synergist (SV1) EC and endosulfan EC were 37.6 and 13.0, 9.84 and 7.75, 54.0 and 7.28 respectively. All of them showed rather high selective toxicity. The STRs of fenvalerate EC, dimethoate EC and methomyl EC were all very low, ranging from 0.02 to 0.21, indicating their low degree of safety to the two species of ladybirds. The results demonstrated that imidacloprid WP and imidacloprid+SV1 EC not only had rather high toxicity to the aphids, but also reduced strikingly the reproduction rate and fecundity of the survival aphids. Insecticides can induce the relative fitness of insects decrease. Among the six insecticides tested with M. persicae, the following were insecticides and the order of induction was: imidacloprid + SV1> imidacloprid > endosulfan > methomyl > fenvalerate > dimethoate.