748 THE MONTHLY BULLETIN. 



Fertilizers. — Feltilization will undoubtedly prove, after more 

 experimentation has been undertaken, to be one of the best methods of 

 handling root knot by forcing the growth of the root system. Observa- 

 tions seem to show that the nematode confines its operations for the 

 most part to the upper 12 to 16 inches of soil, so that if roots may be 

 forced to grow deep enough they may escape injury. Knowing this 

 fact, deep cultivation is an essential. The soil should be liberally 

 supplied with nitrogenous fertilizers and potash. Potassium salts have 

 been found to be beneficial, especially in potash-poor soils in which the 

 nematode occurs. Changes in appearance of badly infested orchards 

 to which potash has been applied have led many people to suppose 

 that this fertilizer actually kills the worm. Resistance to the attack 

 of the root-knot nematode through stimulation of the plant feeders is 

 undoubtedly responsible for the reduction in numbers of the worms 

 found to be present. It has been found in Germany that the sugar 

 beet nematode removes equally all mineral salts from the roots. If, 

 however, the soil is lacking in a particular mineral, the nematode in 

 taking its equal proportion of all minerals will still further diminish 

 the already depleted supply of that one. Therefore to benefit such 

 a condition one would need to add only that mineral which was orig- 

 inally lacking. This may explain the effect of potash in combating 

 this disease. 



Field Control No Crops Present. 



Chemicals have been experimented with in the control of the root- 

 knot in the fields where no crop is present and here again, owing to 

 the great cost incurred in purchasing and applying, they can not be 

 recommended. Of the various chemicals that have been experimented 

 with, carbon bisulphide gave the best results. To successfully destroy 

 the worm 4 ounces must be used per square yard and, as crude carbon 

 bisulphide costs 10 to 15 cents a pound, the cost of the chemical per 

 acre, without considering the necessary labor required, would range 

 between $120 and $180. The cost of other chemicals experimented 

 with have this same fault. However, in small areas, and in places 

 where a tree is to be planted, carbon bisulphide may be used effectively; 

 in doing so the tree is given an opportunity of obtaining a vigorous 

 start and will establish its roots below the area occupied by the worm. 



In 1906 Prof. Bessey carried on numerous experiments with various 



commercial fertilizers at Monetta, South Carolina. The results of this 



experimentation showed that fertilizers applied in sufSciently large 



quantities are valuable in producing crops in a nematode-infested 



region. The following extract from Prof. Bessey 's "Root-knot and 



its control"'' will give an idea of the work that has been done with 



fertilizers : 



"*' * * The following fertilizers were tested in IDOO. mostly in one twentieth 

 acre phats separated by ditches (or rather, very deep furrows) 2 feet wide, the 

 numbers in parentheses I'eferrinn' to the fiekl numbers of the plats: (12) Kainit, 

 1,000 pounds per acre; (13) ammonium sulphate. (107 pounds per acre; (14) 

 kainit, 500 pounds per acre; (!.'')) hish-grade potassium sulphate, 1,000 pounds 

 per acre; (16) check; (17) hiuh grade potnssium sulphate, IiOO pounds per 

 acre; (IS) 17 per cent acid phosphate, 1,000 pounds per acre; (19) 17 per cent 

 acid phosphate, 1 ton per acre ; (20) check. In 1907 the following tests were 



=Root-knot and its Control, by Ernst A. Bessey, Bulletin No. 217, Bureau of Plant 

 Industry, U. S. Dept. Agri. 



