Miorobiol:12 



Perhaps that supposedly stillborn child was, indeed, buried alive and 

 will yet eventually overcome his dyspnea. 



Application of pesticides to plants can conceivably alter root surface 

 microfloras. Most of the investigations conducted to date with pesti- 

 cides have been concerned with effects on the soil, rather than on the 

 rhizosphere population. There are a few reports (^2,^3) that sub- 

 lethal doses of 2,U-D reduce the nodulation of legimes. There are 

 other reports (5U,55,56) that chlorinated insecticides applied at field 

 rates do not interfere with the nodulation of legumes. Data concerning 

 the effects of herbicides and pesticides on the rhizosphere populations 

 are too limited for any satisfactory evaluation of such effects. 



Yet, another way in which the microbial population of the soil may be 

 altered is by the use of soil fumigants. I am sure that, in a meet- 

 ing of this type, soil fimigants have been, or will be, discussed in 

 far greater detail than I can possibly hope to duplicate. In closing, 

 I will simply note that soil fumigants, designed to rid the soil of 

 undesirable microorganisms and noxious weed seeds, do have drastic and 

 long-lasting effect on the soil microbial population. Fumigation 

 treatments may variouly influence the root microfloras. Martin and 

 co-workers (57,53) and Bliss (59) have given some special attention to 

 these effects. Bliss has shown that control of Armillaria on citrus 

 roots by use of carbon disulfide is not due to direct fungicidal action 

 of the disulfide on the parasite, but rather is due to the killing of 

 many species of soil fungi, allowing Trichoderma to become dominant. 

 Trichoderma then invades the boundaries of infected host root tissues 

 and attacks Armillaria , which is not directly killed by the carbon 

 disulfide. Like so many problems connected with the rhizosphere, the 

 part fumigation plays in controlling the root surface microflora de- 

 serves further study. 



REFEHENCSS 



1. Clark, F. E. Adv. Agron. 1: 2hl-288. 19h9. 



2. Katznelson, H., Lochhead, A. G., and Timonin, M. I. Botan. Rev. 



lU: 5U3-587. 19U8. 



3. Harley, J. L. Biol. Rev. 23: 127-158. 19U8. 



h. ffi-ltner, L. Arb. deut. landw. Gesell . 98: 59-78. 190U. 



5. Webley, D. M., Eastwood, D. J., and Gimin^ham, C. H. J. Ecol. 



UO: 169-178. 1952. 



6. Lundegardh, H. Der Kreislauf der Kohlensaure in der Natur. 



G. Fischer, Jena. 192U. 



7. Barker, H. A., and Broyer, T. C. Soil Sci. 53: l467-h77. 19h2. 



8. Stille, B. Arch. Mikrobiol. 9: U77-U85. 1938. 



9. Lyon, T. L., and Wilson, J. K. N. Y. (Cornell) Agr. Expt. Sta. 



Mem. UO: 1-UU. 1921. 



10. Rovira, A. D. Plant and Soil 7: 178-19U. 1956. 



11. Winter, G. Orion 7: 377-301. 1952. 



12. Gyllenberg, H. G. Canad. J. Microbiol. 3: 131-13U. 1957. 



