| With the promotion of farmland rotation and fallow systems,the improvement of arable land quality,and other problems such as soil ecological damage caused by the large-scale use of chemical fertilizers and pesticides,the area of green manure crops has gradually expanded,but green manure crops may become suitable hosts for pests,thereby causing pest populations and increases the risk of outbreaks.Spodoptera frugiperda is a major multi-eating migratory pest that newly invaded our country in 2019,which caused great harm to corn and other food crops,but it is unclear whether green manures will pose a risk to its occurrence.Although the main green manure crops(Vicia sativa L.,Astragalus sinicus L.and Vicia villosa Roth)have been shown to have significant adverse effects on the growth,development and reproduction of Mythimna separata,but the physiological mechanisms is unclear.Therefore,this study obtained the life table parameters of S.frugiperda fed on three green manure crops by established an age-stage sex population life table,predicted the dynamic changes of S.frugiperda population based on the life table,and tested the feeding The flying ability of S.frugiperda on three kinds of green manure crops laid the foundation for the fitness analysis and occurrence risk of host plants.At the same time,the mechanism of three kinds of green manure adversely affected the growth and development of M.separata and further explored from the aspects of nutrition and digestion physiology.The specific research results are as follows:1.Effects of feeding three green manure crops on development,reproduction and flight activities of S.frugiperdaThis study established the life table parameters of S.frugiperda population indoors by feeding different green manures by establishing the age-stage bisexual population life table,and established a population dynamic model of S.frugiperda was introduced.The results showed that there were significant differences in the developmental duration,survival rate,and fecundity of S.frugiperda at different stages of fed on different green manure plants(A.sinicus,V.villosa and V.sativa).S.frugiperda that fed on A.sinicus can’t complete its generation development,and the larval mortality rate reaches 100%.Although the development of V.villosa and V.sativa can completed the development of the generation,the developmental period of the generation was significantly prolonged.The larval survival rate,egg production,age-stage specific survival rate and population generation number in the next three months were significantly lower than those in the control S.frugiperda(feeding corn).Feeding different plants in the larval stage also had a significant effect on the flying ability of S.frugiperda.The flight time and flying distance of S.frugiperda fed on V.villosa were significantly less than that of corn,indicating that feeds on V.villosa can significantly reduce the flying ability of S.frugiperda.According to the results of this study,an ecological control technology for expanding the winter A.sinicus,V.villosa or V.sativa planting areas in southern China to prevent and control the major crops,wheat and corn pests,S.frugiperda,has been proposed.This technology can cut off the life history of S.frugiperda in perennial occurrence areas and wintering areas,thereby reducing the number of insect sources2.Effects of feeding three green manure crops on nutritional physiology of M.separataThe feeding amount and nutrition utilization of M separata on three green manures,A.sinicus,V.villosa and V.sativa effects of their secondary metabolites were determined using Zea mays L.as the control in this study,the composition of nutrition and secondary metabolites in four plants were analyzed.The results showed that the feeding on green manure crops in the larval stage had significant effects on the feeding,food utilization,food conversion,digestibility and larvae growth of M.separate.Overall,the relative growth rate,relative feed intake,food utilization rate and conversion rate of 5th instar larvae fed on green manures were significantly lower than that on control,and the approximate digestibility was significantly higher than that of corn.In addition,the total protein content in tested plants was significantly negative correlated with the relative feeding rate of larvae.There was no significant correlation between the content of secondary metabolites flavonoids,tannins,total saponins,and total phenols and the feeding amount of M.separata larvae.There were significant differences among the the nutritional effects of sinicus,V.villosa and V.sativa on M.separata larvae,but they were not conducive to the growth and development of M.separata larvae.Therefore,the potential possibility of these green manures as natural hosts of this pest is low.The broad plantation of these green manures should not contribute to the outbreak of M.separata.3.Effects of feeding three green manure crops on enzyme activity of M.separataThe activities of midgut digestive enzymes,protective enzymes.and detoxifying enzymes of M.separata feeding on different green manure plants were measured to clarify the interaction mechanism between M.separata and green manures.The results showed that feeding on green manure crops had a significant effect on the changes of midgut enzyme activity of M.separata larvae.Among them,the protective enzymes(peroxidase activity(POD))and detoxifying enzymes(carboxylesterase(CarE),cytochrome P450 enzyme(CYP450)were significantly higher than those of the control group(corn).The protease activity of larvae fed on A.sinicus was significantly higher than that of the other treatment groups,but the lipase activity was significantly lower than that of the other treatment groups;the amylase activity of V.villosa was also significantly lower than that of the other treatment groups.There was no significant difference between the activities of catalase,superoxide dismutase and glutathione S-transferase in armyworm larvae fed on green manure crops.The difference may be caused by the defensive response of the M.separata to feeding unfavorable substances,which also lays a theoretical foundation for further research.The results show that the promotion and planting of A.sinicus,V.villosa and V.sativa,not only will not cause large outbreaks of M.separata and S.frugiperda,but it will also provide a theoretical basis for the technology of ecologically controlling pests by using the cultivation mode of green manure and crop rotation. |
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