BIOLOGICAL CONTROL OF GINSENG ROOT ROTS WITH SOIL AMENDMENTS

The phenomenon of 'soil sickness' is one of the most important limiting factors for ginseng(Panax ginseng) production in Korea. The principal cause is known to be due to the root rots caused by Cylindrocarpon destructans and Fusarium solani. Attempts were made to control the root rots with non-polluting cultural methods or soil amendments. Among the nine soil amendments tested, crab shell, cow bone and pig feces were selected for further testing. Each of the three amendments increased the populations or various actinomycetes in the range of 10-25 times over that of non-amended soil, whereas the population of C. destructans was reduced to about $50-70\%$ as compared with the control. Five isolates of Streptomyces with clear zones on chitin-agar medium were selected and then tested for their antagonistic effects on C. destructans. When anyone of the five isolates of Streptomyces and C. destructans was grown together in a modified peptone broth, growth of the latter was highly inhibited. When three levels of crab shell, cow bone, or pig feces were used to amend potted soil infested with C. destruetans, the root rot ratings of ginseng seedlings were reduced to less than one half in all the treatments as compared to the control. In another similar experiment, crab shell and cow bone amendments resulted in almost complete control of the seedling root rots in soil infested with C. destructans or F. solani. In conclusion, biological control with soil amendments of ginseng root rots caused by C. destructans and F. solani was successful. Further basic studies should be pursued using soil amendments for better control. In addition, field experiments are needed to complement the soil amendment control measures in an integrated pest control program.