CHAPTER III 



SOIL SICKNESS DUE TO THE PRESENCE OF PARASITES 

 HARMFUL TO PLANTS 



When a soil is sick because its beneficial bacteria 

 do not perform their functions properly, or because 

 of abnormalities in its chemical properties, careful 

 treatment and proper cultural methods will restore 

 it to health. But when a soil becomes sick and un- 

 productive because parasitic forms gain a foothold 

 there, much greater skill and knowledge are required 

 to cope with the problem. Its solution is of the 

 greatest economic importance to the trucker and 

 gardener. 



Parasitic fungi finding their way in a soil do not 

 necessarily interfere with the work of the beneficial 

 bacteria, such as the ammonifiers and nitrifiers, for 

 instance. Neither do they always influence the 

 chemical or physical nature of the soil. They attack 

 directly the crop itself. Of the numerous parasites 

 rendering soils unproductive, we will consider here 

 only two types. 



I. Soil Sickness Due to Parasitic Fungi. 

 Fungi which produce damping off in seedlings. 



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