Population Dynamics Of Asian Citrus Psyllid And Potential Assessment Of Aspergillus Combined With Insecticide For Pest Control

Huanglongbing,HLB is a devastating disease of citrus which seriously threatens the healthy development of citrus industry in the world.Asian citrus psyllid Diaphorina citri Kuwayama?citrus psyllid for short?is the major vector of HLB pathogen.Therefore,in order to prevent effectively the harm of HLB,it is necessary to strengthen the control of citrus psyllids in citrus producing areas.Guangxi citrus planting area and output rank first in China.In this dissertation,The citrus psyllid was used as the research object,While clarifying the dynamics of the lost citrus orchard in Guilin Guangxi,through separation and purification field parasitic fungus on citrus psyllid identification,on the basis of evaluation of insect fungal virulence of citrus psyllid.based on the requirement of biochemical coordinated control pollution,evaluating fungus and the compatibility of chemical insecticides,for citrus psyllid in the field of the green prevention and control to provide basic data.The main results are as follows:1.Population dynamics of citrus psyllid in the lost citrus orchard in Guilin GuangxiFrom March 2019 to December 2019,a systematic survey of dynamic population of citrus psyllids in 6 lost citrus orchards which in Guilin Guangxi.The result seems that the largest population of citrus psyllids was from June to September,and break out easily.Among them,the number of adults was the highest in mid-August.In late September,as the temperature gradually decreased?the minimum temperature on a single day was lower than 24??,the number of nymph emergence decreased sharply.Adults of citrus psyllids are overwintering populations after October.Therefore,in Guilin Guangxi,effectively and timely control of citrus psyllid in summer and autumn,and paying attention to clearing the garden in winter were beneficial to control the population of citrus psyllid.2.Identification and virulence determination of parasitic fungus of citrus psyllidA strain of Aspergillus sp.was isolated and purified from citrus psyllid collected in the field.Koch method was used to confirm the fungus's infectivity to citrus psyllid.After the joint identification of molecular biology and morphology,the fungus was confirmed to be Aspergillus aculeatus and named Aspergillus aculeatus YS-1.The toxicity of Aspergillus aculeatus YS-1 to adult citrus psyllid was determined by spray method.After spraying the fungus for 5 days,the lethal concentration LC₅₀ of Aspergillus aculeatus YS-1 to adult citrus psyllid was 3.017×10⁶ spores/mL,which was a highly pathogenic strain.3.4 compatibility of insecticides with Aspergillus aculeatus YS-1 and determination of co-toxicity coefficient against citrus psyllid.Through the influence of four insecticides?imidacloprid,thiamethoxam,chlorpyrifos and bifenthrin?with Aspergillus aculeatus YS-1,on the mycelia growth rate and spore germination rate.The result seems that Chlorpyrifos has the greatest inhibitory effect on spore germination and mycelia growth of Aspergillus aculeatus YS-1.Imidacloprid,thiamethoxam and bifenthrin inhibited the germination of Aspergillus aculeatus YS-1 to some extent,but not significantly.Four kinds of pesticides were mixed with Aspergillus aculeatus YS-1 in a 1:1 volume,and the co-toxicity coefficient of the mixture to citrus psyllid was measured.It was found that the combination of imidacloprid and Aspergillus aculeatus YS-1 had a synergistic effect;The combination of permethrin/chlorpyrifos and Aspergillus aculeatus YS-1 has an additive effect;the combination of thiamethoxam and Aspergillus aculeatus YS-1 has an antagonistic effect.Therefore,the combined use of Aspergillus aculeatus YS-1 with imidacloprid or bifenthrin can improve the control effect of citrus psyllid and has the potential of field application.However,thiamethoxam and chlorpyrifos are not recommended to be used in combination with this fungus.