Studies On The Dynamics Of Arthropod Communities And The Relations Of Main Pests With Their Natural Enemies In Eggplant Field

This thesis came from the project "Special Fund of Anhui Province Governor (y47)—integrated pest management and application for the non-environment damage vegetables".Based on ecological investigation,the dynamics of the arthropod communities in eggplant field and interaction of main pests with its natural enemies were studied by means of community analysis,path analtsis and geostastics,etc.These will provide theory foundation for IPM of pests lived in eggplant field.(1) The arthropod total community was divided into phytophage,predacious,parasiticneutrality sub-community according to species' nutrition and predator-prey relationship. Components of the total and each sub-community were analyzed by number of groups, individual numbers and some other ecological indexes.In 2006,25 species were got which belonged to 47 families.Pytophage was prominent part of the arthropod total community, its relative abundance was 0.9939,its dominant species was Bemisia tabaci;and that of predacious sub-community was 0.0052,dominant species were Therdion oslumaculatum and Orius minutus.In 2007,44 species were got which belonged to 37 families, phytophage was also prominent part,its relative abundance was 0.9157,its dominant species was Bemisia tabaci and Aphis laburni;and that of predacious sub-community was 0.0746,its dominant species was Therdion oslumaculatum and Orius minutus.Dominant concentration and dominance in two years were compared and the result indicated phytophage sub-community＞total community＞predacious sub-community,and fact of the diversities indexes were predacious sub-community＞total community＞phytophage sub-community.The results of two years above were the same,which was caused by large number of the dominant population.(2) Caused by interaction of pest with its natural enemies and climate factors,indexes of every community fluctuated up and down.Diversity index in two years of total community change gradually,the total community and phytophage sub-community both have low value because of the large individual number of Bemisia tabaci;while predacious sub-community kept in a high level all the time which shows natural enemies are in great charge of pests.(3) The relations between diversity indexes and other ecological indexes in every community were analyzed by Palb analysis in two years.Evenness had close relationship and great direct interaction with diversity indexes in total community;richness,species numbers,dominant concentration,dominance all influenced diversity indexes.So was diversity indexes of phytophage sub-community in 2006,but it was most relative with evenness,species and richness in 2007,the dominant concentration had the greatest interaction.And diversity indexes of predacious sub-community in 2006 was in relation to species numbers and had great direct interaction,while it was evenness in 2007.(4) Total community in two years in different time was analyzed by clustering.The result in 2006 revealed that the total community could be divided into 4 clusters when D is 0.93;so did the total community in 2007 when D is 0.96.The clustering results revealed the differences and complexity of population in different peorids.The optimization partitions in the arthropod total communities in 2006 was 7.7～7.14,7.21～7.28,8.4,8.11～8.25;while it was 4.30～5.14,5.21～6.4,6.11～7.2,7.10～7.15 in 2007.(5) The characteristic parameters of arthropod total community and its phytophagous,predacious sub-community in eggplant field in two years were analyzed with the method of principal component analysis.The results showed that in 2006,the contribution in the first principal component of arthropod community,phytophagous sub-community and predacious sub-community was 59.42%,71.08%and 63.33%respectively.For the three kinds of communities,the absolute values of normalized regressive coefficient of H' (diversity indexes),J(evenness) and S(species numbers) were larger,indicating that H', Jand S had greater contribution;in 2007,the contribution in the first principal component of arthropod community,phytophagous sub-community and predacious sub-community was 86.23%,81.73%,65.73%respectively.For the three kinds of communities,the absolute values of normalized regressive coefficient of C,D,J and H' had greater contribution.(6) The analysis to the population dynamics and space pattern of Bemisia tabaci in two years was carried on using the aggregated-intensity index and geostatistics methods.The results indicated that Bemisia tabaci has demonstrated the obvious spatial structure and semi-variogram of them could be described by spherical model.This means that Bemisia tabaci occurs in aggregation pattern no matter is the horizontal direction or the vertical direction in eggplants,moreover this aggregation was caused by their own accumulation behavior.(7) Systematical investigation on population dynamics ofBemisia tabaci and its natural enemies in all stages of megranate growth were conducted.The relationship between population of natural enemies and Bemisia tabaci population size in two years was analyzed with the grey system theory and method,and so was the relational grade of various natural enemies to ideal dominant natural enemies.The results showed that Therdion octomaculatum,Orius minutus,Erigonidium graminicolum were the major natural enemies affecting Bemisia tabaci.The individual numbers of Therdion octomaculatum was the largeast,but the relationship with Bemisia tabaci was not the maximum because it predates many kinds of pests.