The synergistic toxicity of spirotetramat mixed with thiamethoxam to Bemisia tabaci were measured by insecticide‐impregnated filter method ,and the results showed that the co‐toxicity coefficient (CTC) ranged from 122.97 to 167.43 ,showing the synergistic effect .Based on the result above ,40% mixtures of spirotetramat and thiamethoxam SC were made , and its toxicity and control efficacy on B . tabaci and its safety to ornamental chrysanthemum cultivars were studied .The results showed when the active ingredient was 90 g a .i . ·hm-2 ,which was the recommended dose ,double dose 180 g a .i . ·hm -2 ,and quadruple dose 360 g a .i . ·hm-2 ,respectively . The mixtures of spirotetramat and thiamethoxam had no significant impact on the growth of three ornamental chrysanthemum cultivars ,Calendula of f icinalis and Callistephus chinensis and Tagetes erecta .So the compound was safe to ornamental chrysanthemum cultivars . After spraying , the control effects of 40% mixtures of spirotetramat and thiamethoxam SC with under 60 -90 g a .i . ·hm -2 treatment could reach 75.60% -90.67% , which was higher than that of mixtures of 22.4% spirotetramate SC and 25% thiamethoxam WG treatments . Therefore the mixtures were proved to have available and persistent control effect against Bemisia tabaci .%采用滤纸药膜法测定了螺虫乙酯与噻虫嗪混配对菊花烟粉虱的联合毒力，测定共毒系数CTC为122.97～167.43，表现增效作用。据此确定最佳配比，配制成增效混剂40％SC，并研究了其对菊花烟粉虱的毒力和防效及其对观赏菊花安全性，结果表明在推荐有效成分剂量90ga．i．·hm－2、二倍量180ga．i．·hm－2及四倍量360ga．i．·hm－2下对金盏菊、翠菊、万寿菊等3种观赏菊花植株生长无明显异常影响，具有较好的安全性；田间药效良好，其用量60～90ga．i．·hm－2的效果达75.60％～90.67％，优于22.4％螺虫乙酯SC和25％噻虫嗪WG。该增效混剂防治菊花烟粉虱的速效性和持效性皆佳。
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