| Peanut is an important oil crop and commercial crop in our country.Aphis craccivora is one of the main pests of peanuts.It has the characteristics of wide distribution,rapid propagation,and transmission of multiple viral diseases,especially during the early growth period of peanut.In recent years,the occurrence of A.craccivora was increased significantly,which seriously affected the yield and quality of peanuts.At present,chemical control is still the main control method of A.craccivora,but because of its high concealability and strong reproduction,the control effect is not good,and long-term application of chemical agents is easy to lead to aphid resistance,killing natural enemies and other problems,which is not conducive to the sustainable development of peanut ecosystem.With the vigorous advocacy of green agricultural production by the state in recent years,ecological pest control technology has been widely studied and applied by planting functional plants in a single crop field to conserve natural enemies and enhance natural control effect of natural enemies.In this study,two groups of functional plants treatments are formed by planting Hibiscus cannabinus and Ricinus communis adjacent to peanut,and peanut-functional plant micro-landscapes were taken as the research systems.The population dynamics of major predatory ladybugs(i.e.,Harmonia axyridis,Hippodamia variegata and Propylaea japonica)and A.craccivora in these micro-landscapes were studied.Furthermore,the effects of H.cannabinus and R.communis on the behavior,survival and reproduction of H.axyridis were evaluated through indoor tests.The major results are as follows:1.Effects of H.cannabinus and R.communis on population dynamics of A.craccivora and predatory ladybug in peanut fields.The flowers of R.communis began to bloom in mid-June and the full flowering period is in late June,which can provide food and habitat for natural enemies in the early and middle stages.H.cannabinus began to bloom in early July and the full flowering period is in early August,which can provide food and habitat for natural enemies in the middle and late stages.In the control area(peanut mono-crop area),the total occurrence of H.axyridis,H.variegata and P.japonica during the whole survey period were 1.00 head/m~2,4.99 head/m~2,and 1.00 head/m~2,respectively.In H.cannabinus treated area,the total occurrence of H.axyridis(58.00 head/m~2),H.variegata(51.00 head/m~2),and P.japonica(7.33 head/m~2)were significantly higher than those of the control area.In R.communis treated area,the total occurrence of H.axyridis(43.00 head/m~2)was significantly higher than that of the control area,but the total number of H.variegata(8.83 head/m~2)and P.japonica(3.33 head/m~2)had no significant differences compared with the control area.H.cannabinus attracted more H.axyridis than R.communis from July 27 to August 16,with1.89 head/m~2 and 1.22 head/m~2 occurring,respectively;on June 8 and from June 29 to July 13,the attraction effect of H.variegata on H.variegata was significantly higher than that of R.communis,with the occurrence numbers of 0.89 head/m~2,3.22 head/m~2,7.89 head/m~2 and 2.00 head/m~2,respectively;on July 6,the attractant effect on P.japonica was significantly higher than that of R.communis,with the occurrence number of 1.11 head/m~2.On June 8,the population of H.axyridis on R.communis(0.22 head/m~2)was significantly higher than that on H.cannabinus.These results indicated that H.cannabinus had a significant attraction effect on these three predatory ladybugs,showing the significant potential for attracting predatory ladybugs.R.communis significantly attracted H.axyridis,but did not attract or conserve H.variegata and P.japonica.Compared with peanut mono-crop areas,there were no significant differences in the total occurrence of A.craccivora in peanut patches in H.cannabinus treatment area or R.communis treatment area,indicating that the population of A.craccivora was not effectively controlled.2.Olfactory reaction of H.axyridis on H.cannabinus and R.communisTo clarify the effect of H.cannabinus and R.communis on the olfactory selection behavior of H.axyridis adults,the Y-tube olfactometer was used to test the olfactory taxis of female and male adults to the flowers and leaves of H.cannabinus,R.communis,and peanut leaves in vitro.The results showed that compared with blank control,both female and male adult H.axyridis showed obvious taxis response to the flowers and leaves of H.cannabinus and R.communis,but not to peanut leaf.The selective response rates of both female and male adults were in the order of R.communis leaves>H.cannabinus leaves>H.cannabinus flowers>R.communis flowers>peanut leaves;the selective response rates of female adults were 83.93%,72.73%,66.06%,64.57%and 56.63%,respectively;the selective response rates of male adults were 73.68%,70.00%,67.31%,63.28%and 56.16%,respectively.The results indicated that the flowers and leaves of H.cannabinus and R.communis were very attractive to H.axylridis adults.3.Effects of H.cannabinus and R.communis on the ecological adaptability of H.axyridisThe impact of flowers and leaves in vitro of H.cannabinus and R.communis on the survival and reproduction of the H.axyridis adults was determined by laboratory experiments in the presence or absence of target prey A.craccivora.The results showed that in the absence of A.craccivora,H.cannabinus flowers,leaves and R.communis flowers can significantly improve the survival rate of female and male H.axyridis adults.The average survival time of female adults was 11.40 d,8.40 d,and 7.93 d,respectively,which was 4.5 d,1.5 d,and 1 d longer than that of the control group only provided with water.The average survival time of male adult was 13.30 d,8.97 d,and 9.00 d,respectively,which was 6.1 d,1.8 d and 1.8 d longer than that of the control group.The promoting effects of H.cannabinus flowers on the survival of female and male adults were obviously better than other treatments.In the presence of A.craccivora,H.cannabinus flowers significantly improved the survival rate of female and male H.axyridis adults(28.67 d and 29.00 d,respectively),which was 0.87 d and 0.90 d longer than that of the control group fed only with A.craccivora and water;there were no significant differences between the other treatment groups and the control group.Providing flowers and leaves of H.cannabinus and R.communis can significantly improve the spawning capacity of H.axyridis.H.axyridis laid 253.67 eggs in the first 10 days in the treatment group provided with H.cannabinus flowers,228.53 eggs with H.cannabinus,236.83 eggs with R.communis flowers and 221.20 eggs with R.communis leaves,which were significantly higher than that of the control group(201.00 eggs);the promoting effect of H.cannabinus flowers on the spawning capacity of H.axyridis was significantly higher than those of other treatment groups.In addition,the provision of H.cannabinus flowers significantly shortened the preoviposition of H.axyridis,which was 18.97 d and 1 day earlier than that of the control group.However,the preovipositions were 19.67 d,19.63 d and 19.90 d in the treatment groups provided with H.cannabinus leaves,R.communis flowers and R.communis leaves,with no significant differences compared with that of the control group(19.93 d). |
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