Effects Of Different Planting Patterns Of Grass On Main Pests And Natural Enemies In Apple Orchard

Pest is one of the important factors of restricting apple production in China.However,the prevention and control of pests are still dominated by chemical control.It is important to scientifically and rationally solve the problem of relying on chemical pesticides to control pests,leading to the reduction of natural enemies and excessive pesticide residues.Finding effective and eco-friendly pest control methods are urgent for apple production.As a modern management measure,interplanting grass in apple orchard can effectively increase numbers of natural enemies and control pests.It is efficient and safe for pests control.In this study,we invesigated pests and natural enemies in apple orchards with different grassy patterns by the method of five-point random sampling,and identified efffects of different planting patterns of grass on main pests and natural enemies in apple orchard.The results are as follows:1.Effect of planting Medicago sativa on natural enemies in apple orchard with conventional pesticides mode.We invesigated pests and natural enemies on trees and grasses in M.sativa area and clean cultivation area with conventional pesticides mode.The results showerd that numbers of natural enemies on trees and grass in M.sativa area were much more than in clean cultivation area(P<0.05).Numbers on trees were less than that on M.sativa.Total numbers in M.sativa area were 8.80 times of that in clean cultivation area.It indicated that planting M.sativa between apple rows can effectively protect natural enemies from adverse environmental effects such as chemical pesticides,and effectively protect and breed natural enemies.2.Effect of different planting layouts of M.sativa on major pests and natural enemies in apple orchard.We set different planting layouts of M.sativa in apple orchard,which was planted by every row,every two rows and every three rows.Aphis citricola,Lithocolletis ringoniella,tortricidae and defoliator were main pests.Total numbers of pests in area with M.sativa planted by every row were the lowest,which were 0.77 times,0.54 times and 0.43 times of those in other areas.Main natural enemies were Propylaea japonica,Harmonia axyridis,Chrysoperla sinica,Syrphidae.Total numbers of natural enemies on trees in area with M.sativa planted by every two rows were the highest,which were 1.06 times,1.35 times and 1.93 times of those in other areas.Total numbers of natural enemies on grass in area with M.sativa planted by every row were the highest,which were 1.03 times,1.39 times and 1.88 times of those in other areas.After spraying insecticide in orchard,the recovery rate of natural enemies in M.sativa area was significantly faster than that in the natural grass area.Occurence of pests and natural enemies in area in areas with M.sativa planted by every row and every two rows were better than in other areas(P<0.05).However,there was no significant difference between the two planting layouts(P>0.05).Considering the planting cost,the annual ratios of natural enemies to pests and control effect,the planting layout of arrangement of M.sativa planted by every two rows is better.3.Effects of grassy patterns of combined nectariferous plants with natural grass on main pests and natural enemies in apple orchardsA.citricola and L.ringoniella were main pests in combined grassy area and natural grassy area.And A.citricola was dominant species.After increasing the cultivation of nectariferous plants in 2018,the relative abundance of pests in combined grassy area decreased,the community diversity increased.Total numbers of pests decreased by 93.67%,and were less than those in natural grassy area(P<0.05).Main natural enemies were P.japonica,H.axyridis,C.sinica,Orims,Syrphidae and spiders.After increasing the cultivation of nectariferous plants in 2018,species and numbers of natural enemies increased.Especially after mid-August,natural enemies on grass increased significantly.Total numbers of natural enemies on trees increased by 43.96%,and numbers on grass increased by 16.89%.The ratios of natural enemies to pests in combined grassy area were higher than 1:25,and ratios in 2018 were higher than that in 2017.It means that combined grassy pattern of M.sativa,Vicia villosa,Tagetes patula,Tagetes erectas and natural grass in apple orchard is effective on pests control.