32 



A Review of the Various Remedies which have been Applied for 

 Nematode Repression. 



a. TREATMENT BY CHEMICALS. 



In considering the effects of the application of chemical substances 

 to the soil it must be borne in mind that we have to deal with quite 

 a different matter from that of applying fungicides or insecticides to 

 the surface of a branch or leaf. In the case of a leaf or branch we 

 have organs which are more or less protected with a cuticle, thus 

 rendering them to a large extent impervious to solutions which in the 

 case of roots where absorption of nutrients is one of the principal 

 functions the effects are much more injurious. It is well known to 

 physiologists that the roots of a plant constitute one of the most sensi- 

 tive and irritable organs with which we have to deal, and it does not 

 require a very strong solution of any substance in the soil to produce 

 abnormal conditions in the plant. The nutritive solutions contained 

 in the soil w hich the plant utilizes for its food are always exceedingly 

 dilute and even when slightly concentrated by excessive manuring, 

 or by the use of an improperly proportioned and too concentrated 

 fertilizer they greatly injure the plant. Indeed those pathologists 

 who have an extensive opportunity to observe sickly plants not infre- 

 quently have to deal with disorders due entirely in the first place to 

 improper feeding, although the gardener may surmise that the trouble 

 is brought about by some insect or fungous pest which maybe asso- 

 ciated with his plants merely in a secondary manner. What applies 

 to the excessive use of normally nutrient substances would apply with 

 greater force to substances which do not constitute the food of 

 plants and some of which are known to be quite poisonous to them. 

 Chemical solutions for the killing of nematodes in the soil would 

 have to be applied in a very concentrated form and in considerable 

 quantities in order to be effectual, although some experimenters have 

 advocated the homeopathic method of applying remedies. Various 

 chemical remedies, however, have been recommended, many of which 

 have been tried with reported success. These have been applied 

 both in solutions and in a solid form, either upon the soil before 

 planting, or after the plants were set out. Some of those employed 

 by various experimenters are as follows : — Potassium permanganate, 

 Sulfate of Manganese, Tobacco dust. Tobacco decoction, Unslaked 

 lime, Carbon bisulfide, Kainit, Ammoniacal liquor from gas works. 



