| In order to control forest pests effectively by using entomopathogenic fungi,and take full role of the fungi in the control of forest pests in integrated pest management,a proper way for using entomopathogenic fungi is needed. In the present thesis,a new kind of biorational pest control formulation,nonwoven fabric sheets impregnated with Metarhizium anisopliae (NFSM) was studied in detail. Apart from this,field trials against the pine sawyer,Monochamus alternatus and the Asian Longhorn beetle,Anoplophora glabripennis with nonwoven fabric sheets were carried out to invest the efficacy of NFS so as to provide evidence for field application.Shake culture of strain Ma83 (M. anisopliae) was made to decide the optimal culture parameters for seed culture. With biomass as the estimate,single-factor experiments were carried out to select optimal nitrogen source,carbon source and concentrations of nitrogen and carbon sources. The results showed that the optimal nitrogen source was soybean powder and the optimal carbon source was commercial sugar,with their optimal concentrations of 4% and 2%,respectively. The best liquid medium for seed fermenter culture was:soybean powder 4%,commercial sugar 2%,MgSO4-7H:0 0.5%,KC1 0.5g/L,FeSO4-7H2O O.lg/L,K2HPO41.0g/L,pH6.3.In preparation of NFSM,nutrition and environmental factors influenced the mycelium growth and sporulation. With sporulation as estimate,through an orthogonal test experiment,an optimal medium was decided:glucose 2% and soybean powder 4%. The analysis of variance showed that the difference was notsignificant ( a =0.05) with 2% commercial sugar as substitute,and so 2% commercial sugar and 4% soybean powder were selected as the medium for making NFSM. Single-factor experiments showed that an addition of 0.6% peptone benefitted sporulation while agar did not.Environmental factor experiments showed that the optimal temperature and relative humid (RH) were 25 and 95%,especially the optimal initial pH was 6.3-6.5,and the sporulation could reach 3.6-3.7 X108 spores per square centimeter.Bioassay was carried out against 4-5 -instar M. alternatus larvae with 8 M. anisopliae strains and 1 Beauveria bassiana strain with high virulence and sporulation. Each replication of 9 larvae,was sprayed with 1ml conidial suspension (IX108spores per milliliter) and the larvae were raised in incubator at 25 + 1. There were 3 replication per treatment,3 replications per treatment. The beetles were checked everyday and dead ones were kept in a humid chamber to let colonies form for checking fungal infection. The median lethal time (LT50) was calculated. The result showed that Ma83 and Bb202 were the most virulent strains against M. alternatus larvae with LTso at 4.57d and 4.86d,respectively,and infection rate at 85.2% and 84.0%,respectively.NFS impregnated with the 2 selected strains,Ma83 and Bb202,were applied in the field to control M. alternatus. 3 spots with the similar condition were selected for Beauveria,Metarhizium and control spots. One pieces of NFS was hung around every tree at a height of 2.5m above the ground,and every tree were checked hi the whiter to compare the control efficacies of different fungus with the infection rate and the percentage of dead tree as estimate. The results showed that the 2 strains both worked against M. alternatus,with infection rates of Bb202,Ma83 and CK at 1.31%,3.05% and 5.37%,respectively,and the percentages of dead tree at 0.85%,2.71% and 4.59%,respectively. As compared with the control spot,the difference was significant (a =0.05),suggesting that the important role of the 2 isolations against M. alternatus adults. Bb202 resulted in better control thanMa83.The amounts of conidia trapped from the air and on sheet were checked at different intervals. The results showed that it decreased very quickly soon afterreleasing and then slowed down after half a month. A month later after releasing,the Beauveria and Metarhizium conidia on fabric sheets reached 1.155X 108 and 0.922 X 108 spores per square centimeter,respectively,... |
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