菜粉蝶颗粒体病毒与化学杀虫剂混用防治菜青虫及其增效机制研究

STUDIES ON THE SYNERGISM OF P1ERIS RAPAE GRANULOSIS VIRUS AND INSECTICIDES

菜粉蝶颗粒体病毒(PrGV)与多种低浓度的化学杀虫剂混用,对莱青虫的毒力具有明显的增效作用。PrGV与乙酰甲胺磷混用对菜青虫的防治效果和作物的保护率均优于单用PrGV或乙酰甲胺磷,并且混剂中化学杀虫剂的用量也可减少30％～50％。初步认为PrGV感染对虫体乙酰胆碱酯酶(AChE)。多功能氧化酶(MFO)活性的降低是混剂增效的内在原因之一。经PrGV感染的5龄虫,AChE活性降低了37.94％,MFO活性也下降了55.37～78.78％。病毒感染也影响到杀虫剂对MFO活性的诱导作用。由于MFO活性较低,其对药剂的降解力也随之下降,因此有更多杀虫剂可到达作用靶标AChE,进一步抑制原来活性已较低的感染病毒虫体的AChE的活性。

Of 6 insecticides (fenvaleratc,cartap,dimehyopo,acephate,trichorphon,sevin) laboratory tested,all of them in low concentrations when mixed with Pieris rapac GV were far more effective than insecticides or GV used alone. The results of field plot experiments also showed that a mixture of graulosis virus and acephate was more effective against the imported carbage worm than either material alone. The protection effect to the cabbage leaf increased 33. 34 % and 77. 78% when the PrGV + acephate( 1. 53 × 109GIB/1 + 1 60 ppm) was compared with higher concentration of acephats(250 ppm) and 2. 12 × 109GIB/l used alone. This increase was significant when compared with the insecticide used alone at the 5% level.Further studies on the physiological and biochemical basis for the synergism of the mixture showed that the activity of cholinesterase (possibly including isoenzymes) in the larvae infected by PrGV and the larvae treated with PrGV-acephate,decreases 37. 94% and 70. 94% when compared with the check. These decreases were significant at the 1% level. The activity of microsomal mixed - function oxidases (MFO)showed 55. 37% -78. 78% reduction for the larvae affected with PrGV when compared with the check, as well as 116. 62% enhancement of the activity of MFO with acephate treatment alcne. The activity of MFO of PrGV - acephate treament was only 55. 03% enhancement to the check,far less than that of the acephate treatment alone. Due to the lowered activity of MFO. its ability for degrading insecticides would be decreased, and more insecticide (eg. acephate) could reach the target (eg. cholinesteiase). According to the results of biochemical analysis, PrGV application could decrease the insesticide resistance of the imported cabbage worm population, making acephate and other insecticides more effective.