The Techniques Of Pollution-free Against Xylotrechus Rusticus L

Xylotrechus rusticus L. has been become one of the main pests attacking northern poplars of China in recent years. Herein, the highest virulence, Beauveria bassiana BbOl, for X. rusticus L. larvaes was been screened from seven kinds of B. bassiana strains. Then its molecular structure was identified and the biological characteristics and pathogenic factors were analyzed. The pathogenic process of X. rusticus L. larvae by Bb01 was observed and the pathogenesis mechanism was revealed. Two kinds of natural enemy biological to X. rusticus L., Dastarcus helophoroides and Scleroderma guani, were introduced into Beauveria non-woven for prevent experiment in indoor and outdoor. And, trap test to X. rusticus L. in outdoors was carried by black light lamp in different frequencies. The main results are as follows:1. The results of bioassay of 7 different species from B. bassiana to X. rusticus larvae showed that the unknown strain, isolated from the original host, has higher pathogenicity to X. rusticus. Its mortality was 93.33% and corrected mortality was 92.86%. The infection rate of this unknown strain was 85.71%. And, its LT50 and LC50 was 4.69d and 4.77×106mL-1. It shows significant differences in mortality among different strains and B. bassiana has obviously higher pathogenicity than Beauveria brongniartii to X. rusticus.2. The unknown strain was identified by molecular method. Its DNA was extracted by TRIzol method and ITS-4, a general primer in fungus genomes, was selected for PCR. The results of PCR amplification indicated that the sequence length of unknown strain is 573 bp and blast in NCBI database. This sequence was 99% similarity to the strain of Beauveria bassiana and was named as B. bassiana Bb01 strain.3. Improved Martins medium is suitable for the growth of Bb01 strain in B.bassiana. The best temperature and humidity for spores growth and production is 26℃ and 100%. The growth and production of spores are decreased with the extension of UV exposure.4. The virulence of Bb01 strain to X. rusticus adult is low, only 16.67%. Its highest virulence to X. rusticus larvae under 26℃ and 28℃, the LT50 was 2.23 d and 2.58 d. On the other hand, Bb01 strain show the highest virulence to X. rusticus larvae at relative humidity 100% and LT50 is 2.57 d. Strain virulence can be increased by spread of X. rusticus larvae.5. The activities of detoxifying enzyme and protective enzyme were changed significantly in X. rusticus larvae infected by B. bassiana Bb01 strain. The activities of detoxifying enzymes (carboxylesterase, glutathione S-transferase, and acetylcholinesterase) showed increased at early stage and then slowly decreased for resist infection of Bb01 strain. On the other hand, the activities of the protective enzymes (catalase, superoxide dismutase, and peroxidase) showed a similar tendency and up to the peaked at 72 to 96 h post-infection. In addition, the content of protein and the activities of phenol oxidase in X. rusticus larvae showed increased at early stage and then decreased result from the damage of Bb01 strain.6. The external part of X. rusticus larvae body showed different degree of color variation after the infection of B. bassiana. Scanning electron microscopy was carried to observe the spores’germination of B. bassiana, then the germ tube infect through the body wall and the number increased rapidly on the wall surface. TEM results showed that the skin tissues and cells, muscle tissue, fat body, organelles and stomata are damaged in X. rusticus after infect by B. bassiana.7. D.helophoroides and S.guani were used for X. rusticus biological prevention. The results showed that the temperature was obviously effect the hatching of D.helophoroides egg.The hatching productivity was decreased at higher or lower temperature. The parasitic rate of X. rusticus larvae in release rate between larvae and D.helophoroides on 1:100 and 1:3 than directly into the eggs and adults was 100% and 66.67%. However, the parasitic rate of artificial logs simulation on 1:100 and 1:3 release the eggs and the adult was 86.67% and 72.22%. Wood at bareness of xylem has the highest parasitic rate in the experiment of released D.helophoroides adult and egg on several degrees damage on poplar stems surface under semi-natural conditions. The prevention used egg card was a efficiency method. Release of S.guani to control old larvae has high parasitic rate than pupa. The host mortality obviously increased with the increased of natural enemies number. The correct mortality for larvae was 52.13% in the release proportion of 1:5 at semi-natural conditions mortality was, but the recommend ratio is 1:3 for forest. Spores content was declined sustain in 30 d at the non-woven fabric made of 7 strains of B. bassiana in outdoor. Furthermore, B. bassiana Bb01 and Beauveria brongniartii BbCF327 were selected as the best strain for X. rusticus prevention and can be used as reserve strains in forest field.8. The trap test to X. rusticus adults on the outdoors was employed by black light lamp in different wavelengths. The results indicated that X. rusticus adults have phototaxis to low ultraviolet in wave band from 320nm to 368 nm, especially to 368 nm (yellow).20:00 pm to 22:00 pm is the best trap time. The trapping efficiency in a sunny day is better than which in fine overcast and cloudy day. This suggested that black light lamp can be used as an assist technology for X. rusticus adults damage monitor.