300 



Disease-Producing Microorganisms 



for golf greens. Acetic acid (1.2 per cent), applied 10 days before 

 planting, has also been recommended for destruction of soil-infesting 

 damping-off fungi. 



Various other soil fungicides and volatile antiseptics, like carbon 

 bisulfide and toluol, have been frequently employed for destruction 

 of pathogenic fungi. Carbon bisulfide can be used with success 

 against a number of disease-producing fungi. This disinfectant 

 should be applied to the soil free from plants; otherwise the chemical 



7.4 7.2 7.0 6.8 6.6 6.4 6.2 6.0 

 Hydrogen-ion concentration 



5.8 5.6 



Fig. 119. Effect of soil acidity on the percentage of club root (from Chupp). 



will result in plant injury. Good results have also been obtained 

 with toluol in controlling various diseases. 



It is impossible to sterilize the soil completely, especially by the 

 use of high doses of disinfectants, without injuring the plants. The 

 amount of disinfectant necessary to destroy the pathogenic organ- 

 isms in the soil is considerably less than that necessary to sterilize 

 the soil as a whole. Various chemicals vary greatly in this respect. 

 Mercuric chloride is far more active than organic mercuriates; the 

 microbicidal dose for mercury compounds is about the same as the 

 antiseptic dose, whereas for copper salts the antiseptic dose is much 

 lower than the microbicidal. 



When soil is sterilized, the fungi and other plant and animal 

 parasites are readily destroyed. Once certain parasitic organisms 

 are introduced, however, they may develop readily in the treated 

 soil and even cause a larger amount of infection. Treatment of soil 

 with a disinfecting agent followed by inoculation with saprophytic 



