Biological Control On Defoliators Of Dalbergia Odoriferaby

Dalbergia odorifera is one of the precious tree species in China,and its wild resources are decreasing because of the illegal logging.The artificial planting area has increased rapidly in recent years.The occurrence of diseases and insect pests is becoming more and more serious,especially the leaf-eating insects,the ancient cotton moth Orgyia postica Walke and the brown spot yellow poisonous moth Orvasca subnotata Walker,which often breaks out,these pests have seriously affected the growth of Dalbergia odorifera.In this thesis,pathogenic fungi were isolated and identified from the corpse of leaf-eating insects of Dalbergia sibiricum.Mutagenesis on these strains were carried out by ultraviolet radiation.The strains were identified by DNA sequences and phylogenetic analyses.The biological characteristics,conidial spore sporulation,conidial spore germination,toxicity on leaf-eating insects of these strains and their mutagen strains were studied.The main findings are as follows:(1)Isolation and identification of pathogenic fungi of Dalbergia odorifera leaf-eating pests.Strains were isolated from dead larvae of the defoliators Orgyia postica Walke and Orvasca subnotata Walker,and these strains were named as BJJ01 and LJJ01.Two strains of fungi similar to Beauveria bassiana and Metarhizium anisopliae were screened and numbered and molecularly identified.Phylogenetic analyses on the ITS sequences were carried out.ITS sequences of BJJ01 is similar with Beauveria bassiana by 98.5%and ITS sequences of LJJ01 is similar with Metarhizium anisopliae by 99%.Phylogenies show that BJJ01 is nested in Beauveria bassiana clade and LJJ01 is nested in Metarhizium anisopliae clade.So BJJ01 is identified as Beauveria bassiana(Bals.-Criy.)c Vuill.and LJJ01 is identified as Metarhizium anisopliae(Metschn.)Sorokin.(2)UV mutagenesis of pathogenic fungus isolates of leaf-eating pests.The original strains of BJJ01 and LJJ01 were treated by ultraviolet radiation,and the mutagen strains were screened as BJJ01-UV40 and LJJ01-UV60.The larvae of Orgyia postica and Orvasca subnotata were tested by these mutagen strains of BJJ01-UV40 and LJJ01-UV60.The death rate of Orgyia poslica and Orvasca subnotata by BJJ01-UV40 and LJJ01-UV60 treatments were increased by 52%and 35%respectively compared with the tests by their original strains of BJJ01 and LJJ01.(3)Biological characteristics of highly virulent strains of leaf-eating pests.The spore production of the mutagenized BJJ01-UV40 and LJJ01-UV60 were significantly lower than that of BJJ01 and LJJ01,indicating that ultraviolet light can reduce the spore production of Metarhizium anisopliae and Beauveria bassiana.Under 26? and PDA culture conditions,there was no significant difference in the germination rate of conidia of strains BJJ01 and BJJ01-UV60,which indicated that ultraviolet rays have less effects on conidia germination rate of Metarhizium anisopliae LJJ01 and Beauveria bassiana.(4)Field control on Orgyia postica and Orvasca subnotata.Based on the laboratory tests,the field control on larvae of Orgyia postica and Orvasca subnotata were carried out in Hainan Province.The defoliators of Orgyia postica and Orvasca subnotata were decreased by 65.2%,77.3%and 93.8%respectively when treated by spores concentration 1×105/mL,1×106/mL and 1×107/mL of BJJ01-UV40 and LJJ01-UV60.