Species Diversity And Pathogenicity Of Entomogenous Fungi On Diaphorina Citri Kuwayama

The Asiatic citrus psyllid（ACP）,Diaphorina citri Kuwayama（Homoptera:Psyllidae）,is an insect that spreads the Citrus Huanglongbing disease.At present,chemical agents are mainly used to control the D.citri in production.With the concept of"double reduction"of national pesticide and chemical fertilizer application,biological control has been pushed to a new level.Entomogenous fungi play an important role to control agricultural pests in biological control.The investigation of species diversity and pathogenicity of entomogenous fungi on D.citri can provide theoretical basis for biological control of D.citri.Through morphological and molecular biological identification,52species,1033 fungal strains were isolated from the D.citri,including 15species and 710 strains belonging to entomogenous fungi.From June to October 2019,the dominant species of entomogenous fungi were Cladosporium cladosporioides,Penicillium citrinum and Penicillium oxalicum.The pathogenicity of 17 species of fungi to the adults D.citri was determined.The results showed that 4 species of entomogenous fungi,including Lecanicillium psalliotae,Beauveria bassiana,Isaria fumosorosea and Purpureocillium lilacinum,were pathogenic to the adults D.citri.The LT₉₅of the four entomogenous fungi to the adults D.citri were 2.85d,4.65d,6.78d and 45.66d,respectively.The difference of LT₉₅among the entomogenous fungi was significant.The pathogenicity and germination rate of L.psalliotae 7r163 and B.bassiana n67 were studied under different conditions.When the concentration of conidia was 5.0×10⁶,5.0×10⁷and 3.3×10⁸spores/m L,the LT₅₀of L.psalliotae 7r163 strain to adults D.citri was3.67d,2.42d and 2.21d,respectively.The LT₅₀of B.bassiana n67 strain to adults D.citri was 4.46d,3.61d and 3.08d,respectively.The LT₅₀of the L.psalliotae 7r163 strain was significantly lower than that of the B.bassiana n67 strain.When the temperature was 23,27,31 and 35℃,the LT₅₀of L.psalliotae 7r163 strain was 3.92,2.31,2.14 and 2.74d,respectively;The LT₅₀of B.bassiana n67 strain was 5.13,3.67,3.60 and14.82d,respectively.The LT₅₀of L.psalliotae 7r163 strain was significantly lower than that of B.bassiana n67 strain..The LT₅₀of B.bassiana n67 strain to adults and nymphs was 3.61 and 2.28d,respectively.The LT₅₀of B.bassiana n67 strain to adults was significantly higher than that of nymphs.Under 15-35℃,the germination rate of conidia of L.psalliotae7r163 strain was over 99%in PDA medium for 12h,but it could not form colony under 35℃;under 15-31℃,the germination rate of conidia of B.bassiana n67 strain was over 99%in PDA medium for 36h,but it could not germinate under 35℃.The germination rate of conidia of L.psalliotae 7r163 strain was over 99%in PDA and WD medium for 8 h;And that of B.bassiana n67 strain was 2.6%in WD medium for 36h,which was significantly lower than that in PDA medium.The germination rate of conidia of L.psalliotae 7r163 was 35.84%at 92%relative humidity for 36h,and 19.45%at 92%relative humidity for 72 h.The germination rate of conidia of L.psalliotae 7r163 strain was 16.54%in24h when it was exposed to UV for 4min;50.40%in 48h when B.bassiana n67 strain was exposed to UV for 4min.of different liquid culture conditions on the sporulation of L.psalliotae7r163 strain and B.bassiana n67 strain.When p H=5.0,culture temperature is 27℃,initial amount of spore access is 1.0×10⁶spores,and culture time is 5d,the spore yield of L.psalliotae 7r163 strain is the largest;when p H=6.0,culture temperature is 27℃,initial amount of spore access is 0.6×10⁶spores,and culture time is 10d,the spore yield of B.bassiana n67 strain is the largest.