Study On The Population Dynamics And Selection Preference Of Spider Mites To Different Host Plants In Korla Area

Spider mites are important pests that cause heavy damage to a variety of crops,fruit trees and vegetables.The planting structure of crops can influence the species and damage ability of pest mites.By clarifying the population structure and host preference of spider mites in Korla area,it can provide theoretical basis for agricultural control of pest mites.In this thesis,the species,distribution,and occurrence degree of spider mites on crops and weeds in the Korla region were surveyed,and the population dynamics of spider mites on the field crops in Korla region were investigated.The leaf disc test was used to study the selectivity of spider mites to different host plants,intended to screen the preferred host plants of spider mites and propose suggestions for the distribution of crop cultivation.The research results provide a theoretical basis for local spider mite control,ecological protection and research on biological diversity,and also prepare for further research.The main results are as follows:1.The species and occurrence degree of spider mitesA total of 10 harmful mites were found on 8 main crops and 10 weeds.These 10 species of spider mites belong to the genera Tetranychus,Petrobia and Oligonychus.The main harmful mites were Tetranychus dunhuangensis Wang and T.truncatus Ehara.T.dunhuangensis are dominant species of local spider mites because they occur more frequently on most plants than other harmful mites.Bassia hyssopifolia(Pall.)O.Kuntze,Chenopodium album L.,Sonchus oleraceus L.,Mulgedium tataricum(L.)DC.,Convolvulus arvensis L.,and Chloris virgata Sw.are the main overwintering host plants of spider mites before entering the farmland.2.Population quantity and dynamics of T.dunchuangensis and T.truncatus on staple cropsT.dunchuangensis began to occur on the host plants in mid to late June,and T.truncatus began to occur in mid to late July.The number of both spider mites reached peak from late July to early August,and gradually decreased in late August.The two spider mites firstly damaged Citrullus lanatus(Thunb.)Matsum.et Nakai and had the largest populations in Arachis hypogaea L.(The number of T.dunchuangensis is 278.09 ind./plant and T.truncatus is 117.89 ind./plant).The average population of T.dunchuangensis was highest in Amaranthus hypochondriacus L.(67.13 ind./plant/time)and lowest in Zea mays L.(7.86 ind./plant/time),while the T.truncatus was highest in A.hypogaea(17.01 ind./plant/time)and lowest in Gossypium hirsutum L.(0.06 ind./plant/time).The average population of T.dunchuangensis was significantly higher than that of T.truncatus in A.hypochondriacus,G.hirsutum and C.lanatus,but there was no significant difference between two spider mites in Arachis hypogaea,Beta vulgaris L.and Z.mays.3.Host preference of T.dunchuangensis and T.truncatus on different cropsThrough the pairwise host selection experiments in the laboratory,it found that the T.dunchuangensis had the highest feeding selection rate for C.lanatus and S.tuberosum,and the lowest feeding selection rate for Z.mays.T.truncatus had the highest feeding selection rate for G.hirsutum and A.hypogaea,and the lowest feeding selection rate for B.vulgaris.In the oviposition selection test,the T.dunchuangensis has the highest proportion of egg production on C.lanatus(24.40%)and S.tuberosum(24.07%),while the T.truncatus has the highest proportion of egg production on G.hirsutum(29.81%)and A.hypogaea(20.49%).In summary,ten species of spider mites were found on main crops and weeds in Korla.Most species of spider mites were found on S.oleraceus,A.hypochondriacus and A.hypogaea,and the species of spider mites are the least on B.vulgaris,C.lanatus and C.virgata.The T.dunchuangensis is the dominant species of spider mites in Korla region,which occurs early and has a large quantity.C.lanatus and S.tuberosum are its favorite hosts,and Z.mays is the least favorite host.The number of T.truncatus occurring late and has a small quantity,G.hirsutum and A.hypogaea are its favorite hosts,while B.vulgaris is the least preferred host.C.lanatus is the first crop harmed by spider mites,and A.hypogaea is seriously damaged by two species spider mites.The research results provide scientific basis for confidence the key hosts and optimum time to control spider mites,as well as improving crops composition and distribution.