| The important content of pest management is protecting abundance of natural enemies by agricultural practices to enhance biological control of pests in the agricultural ecosystems.Planting functional plants to maintain and increase the natural enemies for biological control of pests in the single crop ecosystem is one of the most important methods.Due to the intensification of apple planting in north China,there are more insect pests and fewer natural enemies.The spirea aphid(Aphis spiraecola)is one of major pests in apple production areas in north China,which had the characteristics of wide distribution,fast reproduction,much generations and serious damage.Planting functional plants in the apple orchards could enhance the natural enemies for biological control of pests in the orchard microlandscape,but the performance of these functions will be affected by the change of functional plant species in the microlandscape.In this study,the spirea aphids and its predatory natural enemies in the apple orchard were considered as research object,the three functional plants(including Orychophragmus violaceus,Cnidium monnieri,and Calendula officinalis)were considered as influence factors,and the microlandscape constituted of apple trees and functional plants were considered as research systems.This study researches on the population dynamics,distribution pattern,transfer and diffusion,predation ability and biocontrol services of spirea aphids and its predators in the microlandscape in Yantai city,Shandong Province in 2018 and 2019.This study aims to reveal the chemical information mechanism of maintain the diversity of natural enemies and their ecological functions in the microlandscape.It provides scientific basis for ecological regulation of pests by planting functional plants.The major contents are as follows: 1.Effects of functional plants on the population dynamics of spirea aphids and its predatorsThe populations of spirea aphids and its predators in the microlandscape constituted of apple trees and functional plants were investigated.The flowers of O.violaceus began to bloom in late March,which can attract predatory natural enemies such as Episyrphus balteata,Propylaea japonica,and Chrysoperla sinica.This plant could provide food resources and habitat for predators in early stage.The density of the predators,such as Harmonia axyridis(0.66 individual per branch),C.sinica(0.22 individual per branch),E.balteata(0.62 individual per branch),and Misumenops tricuspidatus(0.12 individual per branch)on the trees in O.violaceus planting areas were significantly higher than control areas,while the density of the spirea aphids(179.88 individual per branch)on the trees in O.violaceus planting areas was significantly lower than control areas(287.85 individual per branch).The flowers of C.monnieri began to bloom in mid-May,which can attract predatory natural enemies such as H.axyridis,Hippodamia variegate,C.sinica,and E.balteata.This plant could provide food resources(such as pollen,nectar and Semiaphis heraclei)and habitat for predators in middle stage,the largest population of predators was found on C.monnieri.The density of the predators,such as H.axyridis(1.18 individual per branch),C.sinica(1.38 individual per branch),E.balteata(0.53 individual per branch),and M.tricuspidatus(0.28 individual per branch)on the trees in C.monnieri planting areas were significantly higher than control areas,while the density of the spirea aphids(147.38 individual per branch)on the trees in C.monnieri planting areas was extremely significantly lower than control areas(287.85 individual per branch).The flowers of C.officinalis began to bloom in early June,which can attract predatory natural enemies such as E.balteata,H.variegate,C.sinica,and M.tricuspidatus.This plant could provide food resources and habitat for predators in late stage.The density of the predators,such as H.axyridis(0.90 individual per branch),C.sinica(0.13 individual per branch),E.balteata(0.52 individual per branch),and M.tricuspidatus(0.09 individual per branch)on the trees in C.officinalis planting areas were significantly higher than control areas,and the density of the spirea aphids(12.02 individual per branch)on the trees in C.officinalis planting areas was significantly lower than other areas in the second peak period(late August).There was a significant negative correlation between the population of spirea aphids and the total population of predators on apple trees at the occurrence peak of spirea aphids.Further cage exclusion tests showed that the biocontrol services index was high(32.71%)in the planting area of O.violaceus in early,and the biocontrol services index was high(47.56%)in the planting area of C.monnieri at the occurrence peak of spirea aphids.The results showed that planting functional plants has good control effect on spirea aphids.2.Transfer and diffusion of main predators between the functional plants(C.monnieri)and apple treesThe transfer and change of rubidium elements in food chain were detected by trace element marking technology,and the results showed that both the spray and irrigation treatments,Rb could be transferred to the food chain of plants-aphids-predators.In the spray treatment,the Rb content of leaves,flowers,and celery aphids showed a decreasing trend with time,and the Rb content of H.axyridis showed initially increased and then decreased.In the irrigation treatment,the Rb content of leaves,flowers,celery aphids,and H.axyridis showed initially increased and then decreased.The highest Rb content of H.axyridis(0.62 ?g/ml)was found on 3 days after spray treatment.The rubidium marking technology was used to monitor the transfer and diffusion of the main predators(H.axyridis and C.sinica)from C.monnieri to apple trees.The transfer rates of H.axyridis were 44.04% and 66.86% in 2018 and 2019,and the transfer rates of C.sinica were 96.79% and 80.09% in 2018 and 2019.The results showed that H.axyridis and C.sinica could be transferred from the functional plant C.monnieri to apple trees to play a role of biological control.3.Predation functional response and selection preference of H.axyridis to A.spiraecola and S.heracleiAccording to the detection of the predation functional response and selection preference of H.axyridis to A.spiraecola and S.heracleid,each different stage of H.axyridis to A.spiraecola and S.heracleid predation functional responses were Holling ? type,and the female adults of H.axyridis had the largest daily predation of A.spiraecola(143.6 head)and S.heracleid(137.6 head);the female adults of H.axyridis had the strongest predation ability against A.spiraecola(411.28),and the male adults of H.axyridis had the strongest predation ability against S.heracleid(356.40).The searching efficiency of different stage of H.axyridis on A.spiraecola and S.heracleid decreased with the increase of aphid density and showed a significant linear correlation.Due to the interference of self-density,with the same aphid density,the amount of adult H.axyridis predation decreased gradually with the increase of self-density.Under the condition of coexistence of A.spiraecola and S.heracleid,when the total density was low(food insufficient),H.axyridis had no significant preference to both kinds of aphids;when the total density was high(food abundant),H.axyridis showed significant positive preference to A.spiraecola and negative preference to S.heracleid.4.Mechanism of chemical information of C.monnieri attracting H.axyridisIn Y-tube olfactometer assays,H.axyridis adults preferred odors of healthy plants versus blank,and the beetles preferred odors of aphid-infested plants versus blank.The odors of aphid-infested plants in comparison with the healthy plants,H.axyridis adults had no significant differences.In GC-MS and GCEAD trials,two antenna-active components(1,2-diethylbenzene and p-diethylbenzene)were detected among the volatile blends emanating from healthy and aphid-infested plants.Through indoor olfactory behavior and field trapping,both active substances could significantly attract adults of H.axyridis.The results showed that 1,2-diethylbenzene and p-diethylbenzene were the main chemical information substances that attracting H.axyridis.In summary,this study showed that the three functional plants(O.violaceus,C.monnieri,and C.officinalis)could cultivate predatory natural enemies(P.japonica,H.axyridis,H.variegate,C.sinica,E.balteata,and M.tricuspidatus)in the early,middle and later stages of apple trees growth due to their different flowering periods.These predators could be transferred from the functional plants to the apple trees in the microlandscape,and they provided biological control for spirea aphids on the apple trees.In this study,the effects of different functional plants on the spirea aphids and its predators were analyzed,the transfer and diffusion of main predators in microlandscape was tracked,the predation ability and selection preference of H.axyridis to the main preys were studied,the biological control efficiency of the natural enemies to spirea aphids was evaluated quantitatively,the chemical information mechanism of functional plants to maintain the diversity of natural enemies and their ecological functions was revealed,and the pattern,process,mechanism and function of the spirea aphids and its predators in the microlandscape were expounded.It provides scientific basis for establishing the application model of enhancing the biological control function of natural enemies by planting functional plants. |
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