| The fall webworm(Hyphantria cunea)is a worldwide forest pest that causes serious damage to trees.At present,although scholars at home and abroad have done a lot of research on the effects of plant secondary substances on phytophagous insects,but most have focused on model insects,and little is known about H.cunea.In this study,the fall webworm larvae were fed the artificial diets that added to tannin(at 0.20%.0.40%.0.60%and 0.80%),salicin(at 0.50%,0.75%,1.00%and 1.50%),or chlorogenic acid(at 0.10%,0.20%,0.30%and 0.40%),respectively.The effects of plant secondary biomass on the growth and detoxification mechanism of the fall webworm larvae were investigated.It provides a theoretical basis for research and development of prevention and control measures against the fall webworm larvae.The results showed:(1)Effects on the growth and development of the fall webworm larvae.In the tannin-treated group,body weight,body length,head capsule width,body weight gain rate,relative growth rate and special growth rate were all lower or significantly lower than the control group for the 5th instar larvae;there was no significant difference between the treatment groups and the control group for the 4th instar larvae and the treated group was significantly lower than the control group by the 5th instar larvae in the developmental duration;the survival rate was lower than or significantly lower than the control group by the 4th-5th instar larvae.In the salicin-treated group,the body weight,body length,body weight gain rate,relative growth rate and special growth rate of the contents of 0.75%and 1.00%in the treatment group were all higher than or significantly higher than the control group by the 4th instar larvae,and significantly higher than the control group by the 5th instar larvae;the head capsule width for the 5th instar larvae was not significantly diflferent from that of the control group;the treated groups were lower the control group to varying degrees for the 4th-5th instar larvae in the developmental duration;however,there were no significant difference between the 0.50%,1.50%treatment groups and the control group in terms of the body weight,body length,head capsule width and developmental duration of by the 4th-5th instar larvae,and about the survival rate,the treatment groups was not significantly different from the control group for the 4th-5th instar larvae.In the chlorogenic acid treatment group,the body length,body length,head capsule width,body weight gain rate,relative growth rate and special growth rate of the treatment group were all significantly lower than the control group for the 4th-5th instar larvae,the development period was significantly longer in the treatment group,and the survival rate in the treatment group was significantly lower than the control group for the 4th-5th instar larvae.(2)Effects on the food utilization of the fall webworm larvae.Compared with the control group,the amounts of larval food intake and feces produced climded up and then declined as H.cunea larval instars grow in the tannin treatment groups.Food consumption,conversion and utilization by the 4th instar larvae in the tannin groups were not significantly different frol those in the control group.The food consumption by the 5th-6th instar larvae in the tannin treatment groups was significantly higher compared with the control group,but their food conversion and utilization were significantly lower than those of the control.Moreover,the differences in the food consumption,conversion and utilization between a tannin treatment group and the control increased as the increase of larval instars(from 5th to 6th instars).With regard to salicin,food consumption was higher in most treatment groups by the 4th-6th instar larvae,and the amount of feces produced decreased with the increase of the larval instars.Food consumption by the 4th-5th instar larvae from 1.00%salicin treatment group was significantly lower than that in the control group,but they were not different for the 6th instar larvae.There were no significant differences in food consumption for the 4th-5th instar larvae between the other three salicin treatment groups(0.50%,0.75%and 1.50%,respectively)and the control group:however,food consumption by the 6th instar larvae in these three treatment groups were significantly higher than that in the control group.The food conversion and utilization by the 4th-6th instar larvae in 0.50%salicin group were slightly or significantly lower than those in the control group,while 0.75%salicin had no effects of food conversion and utilization for the 4th-6th instar larvae.They were slightly or significantly higher in 1.00%salicin group than that in the control group for the 4th-5th instar larvae,but slightly(not significantly)lower for the 6th instar larvae.At 1.50%salicin,food conversion and utilization the 4th and 6th instar larvae were slightly or significantly lower than those in the control group,but they were significantly higher in the treated groups by the 5th instar larvae.The results indicated that tannin had a significant inhibitory effect on food utilization by H.cunea larvae,whereas the effect of salicin on the food utilization was related to its concentration in the diet,with 1.00%having a promoting effect and 0.5%/1.50%being inhibitory.In the chlorogenic acid treatment group,the feeding amount of the treatment group increased significantly at first and then decreased significantly,while the excrement amount increased significantly at first and then showed no difference with the control group;the food consumption rate was lower in the the treatment group for the 4th instar larvae,and the difference between the treatment group and the control group for the 5th instar iarvae was not significant;the food conversion rate and utilization rate in the treatment group were significantly lower than the control group by the 4th-5th,instar larvae.(3)Effects on the detoxification system of the fall webworm larvae.In the chlorogenic acid treatment group,there was no significant difference in the activity of Glutathion-S-transferase(GSTs)compared with the control group by the 4th-5th instar larvae,and the activity of Carboxylesterase(CarE)was lower than or significantly lover than the control group;Superoxide dismutase(SOD)activity,Catalase(CAT)activity,and the content of glutathione(GSH),Vitamin C(VC)showed no significant difference for the 4th instar larvae;most treatment groups were lower or even significantly lower than the control group by the 5th instar larvae.In each salicin treatment group,the GSTs activity was not significantly different from that of the control group for the 4th instar larvae,and was lower compared with the control group by the 5th instar larvae,and the CarE activity Cas higher than or significantly higher than that of the control group by the 4th-5th instar larvae;SOD activity of the treatment group was not significant different from the control by the 4th5th instar larvae,and the CAT activity was higher than or significantly higher than the control by the 4th-5th instar larvae;the content of GSH and VC was basically higher or significantly higher than the control for the 4th instar larvae,while the content of GSH was mostly lower than the control but there was no significant difference between the the treatment group and the control,and the content of VC was higher or significantly higher than the control.In each chlorogenic acid treatment group,GSTs activity was higher than the control group to varying degrees for the 4th,instar larvae,and lower or significantly lower than the control group by the 4th instar larvae;CarE activity was lower than that of the control group for the 4th instar larvae,among which 0.10%and 0.20%of the treatment group were significantly lower compared with the control group;the 0.40%treatment group was significantly higher than that in the control group,and there was no significant difference between the other treatment groups and the control group;the activity of SOD and CAT was higher than or significantly higher than the control group for the 4th instar larvae;it was much lower than or significantly lower than the control group for the 5th instar larvae.the content of GSH was higher than or significantly higher than that of the control group for the 4th-5th instar larvae,and VC content was significantly higher for the 4th-5th instar larvae.In summary,tannin and chlorogenic acid can significantly inhibit the growth,development and food utilization of the fall webworm larvae,while salicin has a content effect on the influence of the fall webworm larvae,which is shown as promotion within a certain content threshold and interference beyond the content threshold.At the same time,the detoxification system and antioxidant system of the fall webworm larvae were significantly changed under the treatment of three secondary substances.With the extension of chlorogenic acid treatment,the antioxidant enzyme system and detoxification system were inhibited unless the enzymatic antioxidants were significantly activated.Salicin treatment can effectively activate the defense system of the fall webworm larvae. |
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