UNCLASSIFIED PESTS 341 



to grow in the field at any time while attempting to eradicate 

 the disease, since many of them serve as hosts for the 

 worms. 



Where greenhouse soil has become infested by the root- 

 knot nematode, it should either be renewed with fresh unin- 

 fested soil or may be sterilized with live steam under pressure. 

 This is performed by having the beds equipped with lines of 

 pipe running through the soil in which at intervals are small 

 holes about rt inch in diameter for the escape of the steam. 

 The beds are covered with straw or with some other material 

 and the steam is applied until the soil is thoroughly sterilized. 

 This may be determined by placing potatoes in the soil near 

 the surface and when they are found to be cooked the steam 

 may be turned off. Rows of tiles are sometimes used instead 

 of pipes, the steam escaping through the joints. 



More or less satisfactory results can be obtained in shallow 

 beds by applying a weak solution of formaldehyde, 1 part of 

 the 40 per cent commercial solution in 100 parts of water, 

 using 1 to li gallons for every square yard of surface. 



Recent experiments in Florida indicate that land may be 

 freed of root-knot nematodes by the application of com- 

 mercial sodium cyanamid at the rate of 1000 to 5000 pounds 

 to the acre. This material should be applied dry and then 

 worked into the soil. The land should then be irrigated and 

 the crop should not be planted until several weeks later de- 

 pending on the amount of material used. Sodium cyanamid 

 is too expensive for use on large areas but may be employed 

 to advantage on seed-beds and on plots under intensive 

 cultivation. 



References 



Ala. Agr. Exp. Sta. Bull. 9. 1889. 



Mass. (Hatch) Agr. Exp. Sta. Bull. 55. 1898. 



U. S. Bur. Plant Ind. Bull. 217. 1911. 



