Study On Culture Of Metarhizium And Control Against Dendrolimus Punctatus

Metarhizium belongs to a kind of entomogenous fungi with the wide-range host that can infect many agriculture and forestry pests. So there will be wide application prospects to carry on pest biological control in the IPM by utilizing it. At the same time, we also notice that there are a lot of problems to be soluted promptly on the development and production of the Metarhizium preparation and application in the forest. For example, the fungi strain is unstable, sporulation is unsatisfactory, the production technology is unstandard and does not form a complete set, formulation quality is unstable and Metarhizium impacts on bio-diversity and stability of forest species.etc. All these problems have influenced the benefits of the biological control of forest pest in the society, ecology and economics. Research on fungi strain stability, sporulation factor, production quality and application in the forest, and so on, which is the core of the technological problem, offering the scientific direction of theory and foundation in practice for development and application of biological pesticide preparation of Metarhizium. These are significant on theory or on practice, which will engender great society, ecology and economic benefits at the same time.For the reason, we have carried on some research respectively that included the subculture and solid-submerge culture of Metarhizium, the virulence test on the compound formulation of Metarhizium and Beauveria and application of Metarhizium in the forest, etc, which offeres the scientific direction of theory and foundation in practice for the fact that the massive production of Metarhizium and pest control in the forest. The main result of study indicated as follows:Through the subculture of Metarhizium in different medium and carbon-nitrogen sources and proportion of carbon-nitrogen, we discoveried that many of fungi strain appeared degraded properties, such as thin hymeniais, overgrowth or slowgrowth of aerial hyphae, sporulation decline, and virulence reduction, etc. But their degree of variation is not the same. They are equal to appear a similar variation characteristic which is above-mentioned, at different carbon source and nitrogen source or different proportion of carbon-nitrogen culture for M₃₃₇. The result of experiment showed: some fungi strain of Metarhizium represent phenomenon of partial variation in the subculture, the segregant from partial variation whose shape and color is different from the maternal strain. Among them, a variation fungi strain of M₃₃₇ is proved that virulence is obviously lower than the maternal strain through virulence test. At the same time, we noticed the growth speed of M₁₀₃, M₁₀₄ and M₃₃₅ tend towards stability basically in the nutritious and balanced culture of proportion of carbon-nitrogen, such as SDAY and PPDA, and sporulation tends to steady or rise slightly. But M335 and M₃₃₆ appeared that sporulation represents downward trend afterwards in subculture of 6 or 7 generations, which not only relats to the hereditary characteristic of the fungi strain oneself, but also have great relation with the composition nature of the culture at the same time.M₃₃₇ cultivated in the culture of different carbon source appeared that the growth speed of mycelium and production of spore displayed the downward trend in glucose culture, but in lactose and malt sugar as carbon source culture whose growth speed of mycelium andsporulation exhibited upward trend in the subculture. In the culture of different nitrogen source, the growth speed and sporulation of M3j7 appeared to be downward trend through the subculture which took the peanut and wheat bran as nitrogen source, but the speed of growth in the culture taking Soya bean and beef lotion as nitrogen source showed upward trend and then sporulation decline in generations. The experiment for different proportion of carbon-nitrogen showed: the speed of growth and the sporulation of M337 are both increasing in generations when the proportion of carbon-nitrogen of culture is 20/10, which is certain to be useful to steady storage of the fungi strain of M337.Through study of solid-submerge culture technology on Metarhizium indicated that: the quantity of the initial inoculation determines speed of the fungus growth in the liquid fermentation medium, and 10% of the initial inoculation amount is our best choice; The growth and metabolism of Metarhizium are affected by pH.The initial pH of liquid fermentation is approximately 6.0-7.0, which will help to produce spore. The result of experiment indicated: it is the best time for inoculation after 72h when the fungus liquid has been fermented, because the fungus is moderate age, the sporulation is the greatest at this moment, it is also the period that the mycelium grow the fastest and has the most strong vigor, the viscidity of the fungus liquid is high and the seizing to the carrier is good. Though the illumination has certain function on producing spores of some fungi, the result of experiment indicated that Metarhizium cultured in dark does benefit to producing even more spores; Metarhizium needs higher environmental humidity in the course of growth to meet the demand for the moisture in growth of mycelium and production of spores. But it is apt to cause pollution when the humidity is too high. At the same time, high humidity will influence loose degree of the supplies and the state of replenishing air, which is unfavorable to producing spores. This research indicated that it is best to adopt about RH 95%of cultivation. Properly increasing certain supplementary carbon source and nitrogen source does good to production of spores of Metarhizium to some extent. The test indicated that adding 2% sucrose and 0.2% KNO3 solution would have extremely remarkable influence on producing spores. And autoclaving of solid culture can reduce obviously the pollution rate which dropped by 21% approximately compared with what did not have it,at the same time, enhanced producing of spores. Through experiment, we screened out the wheat bran (2), rice bran (2) and the chaff (3) is the best combination; and then it is most rational and economic to cultivate lOd as one production cycle considering shortening production cycle and obtaining the greatest production.The level of the moisture content will influence shelf of spore directly. Result of the test showed that spore powder dried 24h under 35 ^C, its moisture content is approximately 12%, close to industry's standard, and viability of spores can even remain at 83.39% approximately.Through the test of virulence, we found that the compound formulation of Metarhizium and Beauveria has synergism compared with the single formulation of Metarhizium or Beauveria.The virulence of the compound formulation has increased by 1.75 times than the single formulation of Metarhizium or Beauveria.The result of application of Metarhizium in the forest indicated that applying rationally...