The Effect Of Four Pesticides On Paratrioza Sinsca Yang Et Li And The Activity Of Acetylcholinesterase

Paratrioza sinsca Yang et Li is a main pest of the wolfberry. It can cause low harvest of wolfberry. Acetylcholinesterase (AChE) is the target site for organophosphorus and carbamate. So it is important to study toxicity action of organophosphorus pesticide to psylla and the biochemical property of AChE in order to study the resistance and to exploiture of new insecticides.Immersion method was uesed to test the toxicity action of phoxim,triazophos,kung fu and beta-cypermethrin pesticides to the nymph stage of psylla. The results showed that the LC50 of nymphs treated by organophosporus pesticide increased with the increasing of instar,and the effect of triazophos was better than phoxim. The LC50 of nymphs treated by kung fu and beta-cypermethrin pesticides increased with the increasing of instars.The optimal condition for assaying the activity of AChE of the 5th instar nymph and adult of the psylla was determined by the orthogonal matrix method. The activity of AChE of each stage of psylla was determined by the colorimetric method (Ellma modified by Gorun). The results showed that the activity of AChE decreased with the increasing of nymph instar. The specific activity of AChE in 1st instar nymph was the highest (5.147±0.368 nmol·min^-1·mg^-1) and 4th instar nymph was the lowest (0.393±0.008 nmol·min^-1·mg^-1).The median inhibiting concentration (IC50) of triazophos and phoxim to the AChE in nymph stages increased with the activation of AchE increased,separately. The inhibiting effect of triazophos on nymph was better than that of phoxim. The value of Michaelis constant (Km) of AChE in the 2nd instar nymph was the minimum (0.011±0.001mol/L),so the affinity between AChE of the 2nd nymph and substrate was the best among all instars. The hydrolysis efficiency o f AChE to substrate in diffirent instar nymph was 1st > 2nd > 3rd > adult > 5th > 4th by compareing the maximum reaction rate (Vm). The sensitivity of AChE of the 4th nymph for phoxim was more sensitive than triazophos based on the time-course curve of inhibition.