Identification Of High Virulence Of Metarhizium Against White Grubs And The Field Application Research Of New Formulations

The scarab beetle is a gold turtle Branch (Scarabaeoidea), have larvae called white grubs, which cause serious damage to the underground parts of some cultivated plants. Because of a certain degree of secrecy and because they are widespread, the scarab beetle is a kind of underground pest that is difficult to control worldwide, resulting in high costs of pest control each year . Peanut is an important oil crops and food coops in China, which with significant economic value. However, in recent years, the area of incidence of the white grubs expanded into north China such as ShanDong and HeNan province, and the level of damage was increased. But with the high use of poisonous pesticides, the soil and water pollution and other environmental pollution problems have increased and these poisonous pesticides can also affect the quality of agricultural products. Metarhizium. anisopliae is an important biocontrol fungus and there are 200 kinds of insects that can be infected by different strains of Metarhizium. There are reports about Metarhizium being used as a fungus pesticide for controlling underground pests.In this research, the two Metarhizium strains were isolated from natural infected cadaver of peanut grubs in peanut planting base in Rizhao and Qingdao, Shandong Province. The two strains of Metarhizium were named CQM132 and CQM135 respectively. Identified the taxonomic status of the strains and evaluated the virulence of the strains against White grubs indoor. During April to September in 2009～2010, a white grubs biocontrol field trial using different new formulations of Metarhizium anisopliae strain CQMa128 was carried out in randomized plots of a pollution-free peanut production demonstration area in Sanzhuang town, Rizhao, Shandong Province. A preliminary research was conducted on the mixture formulations of Metarhizium anisopliae that suitable for control of underground pest indoor.The main results are as follows:â‘ The two Metarhizium strains(CQM132 and CQM135) were recognized as Metarhizium anisopliae based on the sequence of ITS1-5.8SrDNA -ITS2 and some morphological characteristics as well as according to newly published reference [75].â‘¡The laboratory bioassay indicated that the two strains had a high virulence to the two kinds of white grubs. The corrected accumulative mortality on the two grubs was over 85% with the spore suspension at high concentration(1.1×10⁷spore-mL^-1～ 1.1×10⁸spore·mL^-1)of CQM132, and the LT50 of CQM132 was less than 7.58d; while the corrected accumulative mortality against two grubs was over 90% with the spore suspension at high concentration(1.1×10⁷spore·mL^-1～1.1×10⁸spore·mL^-1)of CQM135, and the LT50 of CQM135 was less than 6.85d. That meant the virulence of CQM135 was more aggressive than CQM132 and could be used as a potential biocontrol agent for white grubs on the peanut production.â‘¢Control effect of Micro Granule:30-40 d after applying 10×10⁸ conidia g-1 on peanut plants at sowing time at a dose of 375 kg/hm2,the mean correction control effect was up to 75.58%～80.03%。The dominance of the natural enemies of the white grub, Tiphiidae in the biocontrol plots investigation showed that Micro Granule of Metarhizium anisopliae CQMa128 have no significant adverse impact on them.â‘£Control effect of Emulsifiable Powder:15-20d after applying 100×10⁸ conidia g-1 Emulsifiable powder onto the young fruit at a dose of 7.5 kg/hm2 the mean control effect was up to 77.59～86.46%. At a higher high dose of the M. anisopliae treatment, the mean protection ratio of peanut was up to 85.76～87.13% and the mean maximum increase in the fresh weight yield of peanuts was up to 832.5～916.4 kg/hm2; therefore, the effect of controlling white grubs and protecting the peanut yield is significant. The dominance of the natural enemies of the white grub, Tiphiidae in the biocontrol plots investigation showed that Emulsifiable Powder of Metarhizium anisopliae strain CQMa128 have no significant adverse impact on them.⑤The pure spore of Metarhizium anisopliae CQMa128 and CQM135 have good compatibility with the high efficiency and low toxicity chemical pesticides cypermethrin, imidacloprid and chlorpyrifos. Indoor bioassay show that the optimal ratio of Mixture formulations of Metarhizium anisopliae CQMa128 and CQM135 with the three kinds of high efficiency and low toxicity chemical pesticides was at the range of 1%–1.5%.