辛硫磷对枸杞木虱的毒力及对其羧酸酯酶的抑制作用

分别采用浸渍法和药膜法测定了辛硫磷对枸杞木虱不同发育期若虫和成虫的毒力，同时测定了辛硫磷对不同龄期枸杞木虱羧酸酯酶（CarE）活性的抑制作用及酶的动力学常数。结果表明:辛硫磷对枸杞木虱的LC50值随若虫龄期的增大而升高，至成虫期再相对降低，其对5龄若虫的LC50值为0.995 mg/L，是对1龄若虫LC50值（0.047 mg/L）的21.2倍。辛硫磷对不同龄期枸杞木虱羧酸酯酶活性的抑制作用I50值及酶的Km和Vmax值也均随着试虫龄期的增大而升高，至成虫期则I50值稍有降低。研究表明，辛硫磷对枸杞木虱的毒力与对其羧酸酯酶活性的抑制作用间存在密切关系，利用辛硫磷防治枸杞木虱时，以选择龄期较低时用药为宜。

Toxicity of phoxim to Paratrioza sinica and inhibition to carboxylesterase of it in different instars

The toxicities of phoxim to Paratrioza sinica in different stages were tested, and the kinetic constants of carboxylesterase (CarE) and the inhibition of phoxim on CarE were also studied. The results indicated that the median lethal concentration (LC₅₀) of phoxim to P. sinica increased with the increase of the nymph stage, but it marginally decreased during the adult stage. The LC₅₀ of phoxim to the first instar nymph was 0.047 mg/L. The LC₅₀ to the fifth instar nymph (0.995 mg/L) was 21.2 times higher than that of the first instar nymph. The K_m and V_max values of CarE in P. sinica increased as the nymph grew older. The median inhibitory concentrations (I₅₀) of phoxim to CarE was also increased with the growth of nymph. The results showed that the toxicities of phoxim to P. sinica were closely related to the activities of CarE in different stages. To achieve good control effect of P. sinica, phoxim should be applied to the small nymph.