Study On Biological Characteristics Of Paecilomyces Fumosoroseus And The Pathologic Changes Of The Infected Cabbage Caterpillar

The entomophilic fungi, Paecilomyces fumosoroseus (Wize) Brown & Smith, is an important pathogen with many host and wide distrbution. The virulence, the biological characteristics of p. fumosoroseus PF9606 and pathologic changes of the infected Cabbage caterpillar were studied in this paper. The results were as follows:1. The p. fumosoroseus PF9606 was suitable to infect the green peach aphid and the young larva of cabbage caterpillar. The infection was obviously increased with the increasing concentration ,while the death rate is reduced with the increasing instar. The values of LC50 was 8.07 ×10~6 conidia/ml agaist the peach aphid and was 9.59×10~6conidia/ml and 1.81×10~7 conidia/ml agaist the cabbage caterpillar in 2 and 3rd larvae.2. The rang of fit temperatures for the mycelian growth of p. fumosoroseus PF9606 was 10~32°C with favourable value of 25~28°C . The rang of fit temperature for producing conidia was 10~30°C with favourable value of 20-25 °C. The best results were obtained when the cultures were under total light. The most suitable culture medium was SDA and SMA, and the appropriate PH for colony growth was 6~7.3. The Effects of carbon resources, nitrogen resources and C/N nutritive medium for mycelian growth and spore yield were tested.The best results were achieved on the culture media of with glucose,and peptone as nitrogen resources and C/N of nutritive medium as 10:l~20:l; it was favourable for the growth and producing spores under 25 °C and 24h full exposure. After inoculated 168h, mycelian biomass and conidia yield were 31.72mg/mg and 24.62 conidia/ml respectively. In addition, mycelian biomass and conidia yield of p. fumosororoseus reached peak after 144~ 168h culture of submerged medium.4. The content of sugar,PH, mycelia biomass and conidia yield in nutritive medium changed obviously with time increaing. After inoculated 120h, mycelia biomass was 22.43mg/ml, and conidia yield in nutritive medium reached 11.8×10~7 conidia/ml. The pH value and the content of sugar reduced gradually in the course of submerged culture p. fumosoroseus PF9606. After inoculated 72h, the initial pH value of the medium dropped from 6.4 to 5.16. So, it was reasonable to regulate the acid alkali degree for the mycelia growth and producing conidia after inoculated 72h. In addition, extracellular protease and chitinase were produced in process of submerged culture.The producing-enzyme level of the fungus had obvious relation with nutrition condition in the submerged culture.5. The rang of fit temperatures for conidial germination of PF9606 was 25~28°C. The favourable RH for conidial germination of p. fumosoroseus Pf9606 was more than 90% and the germination was improved greatly by RH rising. The UV light was unfavourable for the conidial germination ,in addition, the time of residual conidia germination was prolonged greatly. The effects of 8 insecticides on conidial germination of p. fumosororoseus were tested. The results showed that the impact of 8 insecticides was different. In general ,the inhibition was stronger as concentration increasing. The inhibition of tested concentration of 20% fenvalerate, 5% chlorfluauron Ec et al. was lower, so they were good candiate for combined use of fungi insecticides.