232 ROOT-KNOT EELWORM. 



once been found, commonly remains infested agriculturally, 

 and will only produce diseased plants " ; and in a very bad 

 case of infestation under glass which came under my own 

 notice the expense of removal of infested soil, and carting in 

 what it was hoped would remain clean, and also applications 

 which it was hoped might poison the pest, have met with 

 much less success than could be desired. — E. A. 0. 



The kinds of i<oil favourable for gro^rth of root-knot appear to 

 be those which unite lightness and dampness. In such soils 

 the wormlets can travel with the most convenience to them- 

 selves when on their way through the earth to a new settle- 

 ment, and they have also the moisture which is favourable to 

 their vigorous growth. It is stated that "localities highly 

 fertilized with composts, stable manure, or leaf-mould, show 

 the root-knot quicker in plants than in compact or virgin 

 soils, and the worst results are found in gardens planted in 

 long cultivated, fully fertilized, and thoroughly pulverized 

 areas. ... A dry soil with solid growth is . . . unfavourable, 

 hence, in many locations, drainage has entirely changed the 

 character of the land, so that Peaches and Figs grow where 

 they would not before." 



Amongst the details of experiment made under the direction 

 of the Entomologist of the United States Agricultural De- 

 partment, and recorded by Dr. Neal, I do not find that any 

 of the applications were thoroughly remedial. It is stated, 

 however, that alkaline mixtures, 20 to 401b. to each tree, or 

 caustic lime, kainite, muriate and sulphate of potash, or wood 

 ashes, used several years in succession, have come nearest a 

 cure, destroying no doubt many free worms, and inducing a 

 vigorous tough growth of roots more difticult of penetration. 

 But the very large amount of the fertilizer, " not less than 

 3000 lbs. to the acre," which is said to be requisite to produce 

 the required effect, would entail in the case of many chemicals 

 an expense not to be thought of. 



In a series of experiments carefully carried out by one of 

 my correspondents in England, who suffered severely from 

 damage by H. radicicola, he tried the effects of the following 

 chemicals, namely : — " Magnesium sulphate, iron sulphate, 

 tartaric acid, lead acetate, citric acid, sodium sulphite, sodium 

 hyposulphite, sodium caustic, potassium sul]:)hite, j^otassium 

 permanganate, potassium chloride, potassium ferrocyanide, 

 potassium sulphide, potassium sulphate, potassium caustic, 

 potassium acetate, carbolic acid, and potassium cyanide. 

 Gas-lime (fresh), fresh caustic lime, and tobacco powder up 

 to eight grammes." 



Full details of effect or non-effect of these on plant growth 

 and Eelworm life are given in my ' Seventeenth Annual 



