红火蚁不同品级个体的药剂敏感性研究

Susceptibility of different castes of the red imported fire ant(Solenopsis invicta Buren) to insecticides

【目的】红火蚁Solenopsis invicta Buren不同品级的个体在群体生存中担负不同的功能。然而,红火蚁群体中不同品级个体的药剂敏感性还不清楚。【方法】本文采用点滴法测定了氟虫腈、高效氯氰菊酯和茚虫威三类不同药剂对红火蚁各品级个体的触杀毒力,以了解其药剂敏感性。【结果】研究结果显示,红火蚁对不同药剂的敏感性存在显著差异,对氟虫腈最为敏感,高效氯氰菊酯次之,而对茚虫威的敏感性最低,但不同品级个体的药剂敏感性规律却基本一致。有翅雌蚁、有翅雄蚁和蚁后的药剂敏感性最高,3个品级个体的药剂敏感性没有显著差异;除高效氯氰菊酯外,兵蚁的敏感性显著低于有翅蚁和蚁后,而工蚁又显著低于兵蚁。4龄幼蚁对供试的3种杀虫剂的敏感性非常低,致死中量分别为428.77 mg/kg、699.77 mg/kg和1 159.95 mg/kg,比对有翅雌蚁的致死中量高数百至数千倍。对毒力线斜率值的分析发现,同一品级内个体间对不同药剂的敏感性也存在显著差异,对氟虫腈的敏感性表现出品级内个体较大差异,特别是兵蚁和工蚁的敏感性差异最大,其斜率值分别为1.1和1.8,而对茚虫威的个体敏感性差异极小,其斜率值均≥4.7,且工蚁个体间表现出最高的同质性,其斜率值达7.8。【结论】同一品级的个体对不同药剂的敏感性差异没有一致规律,但基本上表现出个体差异较小的特点,特别是4龄幼蚁、有翅雄蚁和蚁后3个品级内个体的药剂敏感性差异较小,其斜率值均≥4.0。本研究的结果为田间防治红火蚁化学药剂的合理使用提供理论指导。

[Objectives] Different castes of the red imported fire ant （Solenopsis invicta Buren） play different roles in the colony. However, the susceptibility of different castes of this ant to insecticides is still not clear. [Methods] In this study, the contact toxicities of three insecticides, fipronil, beta-cypermethrin and indoxaearb, to different castes of the red imported fire ant were measured by topical application. [Results] There were significant differences in the susceptibility of ants to the different insecticides; ants were highly sensitive to fipronil, then to the beta-cypermethrin, and least sensitive to indoxacarb. The susceptibility of different castes to these insecticides also varied. Winged adults and queens were highly susceptible and, with the exception of beta-cypermethrin, soldiers were less susceptible than winged ants and queens. Workers were less sensitive than soldiers. Fourth-instar larvae were the least susceptible to the three insecticides tested; the LD50 values of which were 428.77 mg/kg, 699.77 mg/kg and 1 159.95 mg/kg, respectively. Regression analysis shows that susceptibility to different insecticides differed significantly among individuals in same caste. This was especially true for soldier and worker ants. For example, with respect to fipronil, the slope values for these castes were 1.1 and 1.8, respectively. [Conclusion] However, individuals showed little variation in their susceptibility to indoxacarb, with slope values 〉 4.7 and reaching 7.8 in worker ants. Though we didn＇t observe a general pattern in susceptibility to different insecticides among individuals of the same caste, individual differences were basically low, especially in fourth-instar larvae, winged male ants and queens, all of which had slope values 〉 4.0. These results provide theoretical guidance for the use of insecticides to control fire ants in the field.