用三维坐标评判农药混用对多种害虫的联合作用及综合毒力

Joint action and comprehensive toxicity of pesticides mixture to multiple pests judged with three-dimensional coordinate

在三维坐标内,用3种药剂对害虫的LC50值作理论等效面。3种农药混用后,对害虫LC50实测值的坐标点在等效面上为相加作用,在靠近坐标原点的凹面上为增效作用,在远离原点的凸面上为拮抗作用。在同一坐标内,用3种药剂对几种害虫的LC50值作多个等效面,并将3种农药混用后对几种害虫的LC50实测值标注在坐标内,可以清楚地反映混剂对不同兼治对象的毒力和互作效应。以此研究甲维盐+毒死蜱+吡蚜酮的三元混剂对水稻二化螟、褐飞虱和灰飞虱的兼治作用。结果表明:该混剂对二化螟有显著的增效作用并且毒力最高;对灰飞虱为相加作用,毒力次之;对褐飞虱为拮抗作用,毒力最差。说明该混剂的综合效应差,不适合同时兼治3种害虫。

Within a three-dimensional coordinate, a equivalent plane was drawn on the basis of LC50 of three pesticides against pests. The mixture of the three pesticides had additive effect on pests when LC50 of the mixture was on or near the equivalent plane, had synergistic effect when the LC50 was on the concave near the origin of coordinate and had antagonistic effect when the LC50 was on the convex away from the origin of coordinate. In one coordinate, e-quivalent planes drawn according to the LC50 of three pesticides against different pests and the LC50 of the ternary mix-ture against pests marked in the coordinate could clearly reflect the toxicities and joint actions of the ternary mixture a-gainst different pests. The ternary mixture of emamectin benzoate ＋ chlorpyrifos ＋ pymetrozine against Chilo suppressa-lis Walker, Nilaparvata lugens St？l and Laodelphax striatellus Fall＆#233;n were tested in laboratory. Result showed that joint action of the mixture was synergistic to C. suppressalis, and antagonistic to N. lugens and had additive effect on L-nbsp;striatellus. The toxicity of the mixture was the highest to C. suppressalis, moderate to L. striatellus and the lowest to N. lugens. It was quite clear that the ternary mixture was not good enough to control the three pests simutane-ously.