Influence Of Syringic Acid On The Lethal And Sublethal Effects Of LdNPV Against The Gypsy Moth And Its Mechanism

This study aims to evaluate the effects of syringic acid on the lethal and sublethal effects of the Lymantria dispar nucleopolyhedrovirus(LdNPV)against larvae of the gypsy moth,Lymantria dispar,so as to provide a scientific basis for the prevention and control of this insect pest.Diet plus was used to assess the lethal and sublethal effects of LdNPV with and without syringic acid on the 2nd instar larvae of L.Dispar,The results are as follows:1.The median lethal concentration(LC50)values of LdNPV to the 2nd instar larvae aL.dispar fed on the artificial diets with and without syringic acid were 91.1 OBs/?l and 194.8 OBs/?l,respectively.The median lethal time(LT50)values of LdNPV at the concentration of 2 400 OBs/?l to the 2nd instar larvae fed on the artificial diets with and without syringic acid were 9.3 and 10.1 d,respectively.The median lethal time(LT50 values of LdNPV at the concentration of 24 000 OBs/?l to the 2nd instar larvae fed on the artificial diets with and without syringic acid were 7.8 and 8.1 d,respectively.The higher the concentration of LdNPV,the lower the LT50 value.Syringic acid added in the artificia diet enhanced the lethal effects of LdNPV against L,dispar larvae,and caused the lower LC50 and LT50 values of LdNPV against L.dispar larvae as compared with the diet without syringic acid.2.When the larvae were fed the artificial diet,sublethal effects of LdNPV on larval duration,pupal duration and female adult longevity were not significant;when the LdNPV concentration was high enough,however,the male adult longevity was shortened and the number of eggs laid per female was less than those of the control.Sublethal effects of LdNPV on L.dispar larvae fed on the artificial diet with syringic acid and high concentration of LdNPV were significant:the female and male larval duration was prolonged,the male adult longevity was shortened,and the male emergence rate and the number of eggs laid per female reduced.3.The activity of polyphenol oxidase increased gradually with the time of treatment with normal feed(CK).In the first 60H,the activity of polyphenol oxidase increased with time,and was higher than that in control(CK),which was significantly lower than that in control group(84h).The activity of phenoloxidase was inhibited and the activity was decreased after 36h treatment.The enzyme activity of peroxidase was inhibited at the early stage of treatment,and the enzyme activity was reduced and the enzyme activity of other treatments was more stable in the later stage.