182 Agricultural Gazette. 



been made, all or most of the larvso actually in the soil and unprotected were 

 killed by the poison used. It is plain that the remedy was a good one, thus far ; 

 yet, if the eggs and moulting larvao escaped destruction, because protected 

 by their coverings, tlioy would give rise to galls in the course of a few weeks 

 or months, and the exiicriment would be pronounced a failure. I therefore 

 repeat my suggestion that perhaps a more gradual and longer-continued 

 treatment would bo successful with some of the chemicals already tried and 

 pronounced ineffective. Among those tried are kerosene emulsion ; various 

 solutions of arsenic; bisulphide of carbon; carbolic acid ; the sulphates of 

 ammonium, potash and iron ; the sulphite, sulphide, and muriate of potash ; 

 hyposulphite of soda ; tobacco dust. 



4. Frost. — Dr. Ncal says that if in places where the soil is frozen to some 

 little depth each year the ground bo ploughed at times during the cold season, 

 it is reasonable to suppose that great destruction of the gall-worms will 

 ensue. I know of no experiments demonstrating that the worms will not 

 revive from the effects of low temperature, as they certainly will from those 

 of long continued dryness. 



5. Drainage. — It has long been known that drainage has an important bear- 

 ingon the spread of T. ilei-astntrix. Currenjts of water on or beneath the surface 

 of the soil will pick up and transport small and light objects. Those objects 

 of least specific gravity are most subject to the transporting power of water. 

 Of all the constituents of the soil, none probably are more likely to be thus 

 moved from place to place than minute organisms such as the eggs and 

 larva; of gall-worms ; hence the great importance of drainage in connection 

 with root-gall, as well as with the ravages of T. dc.vastalrix. By a good 

 system of surface drainage, surface-water may be so controlled as to spread 

 the disease as little as possible. It is needless to go into particulars, as any 

 farmer can easily devise a system of drains suited to his individual case. 

 This matter must not, however, bo overlooked by anyone whoso land is 

 infested. It is certain that water is one^of the chief agents in the spread of 

 root-gall. 



6. Famine. — Famine is as destructive to gall-worms as to other animals, and 

 there is not the slightest doubt that land kept quite clear of vegetation will, in 

 time, become disinfected — the worms dying of starvation. How long a time 

 would be required is unknown ; probably more than a year. It is not likely 

 that land will be given up for such a length of time, especially when it is 

 remembered that it must be kept clear of vegetation at considerable expense; 

 but the fact that the worms may be starved out utterly leads to the question 

 whether or not, by a proper rotation of crops, they may not become so 

 reduced by partial starvation as to become comparatively harmless. 



The gall-worm evil, like most evils, is endurable so long as it does not 

 become too great. It is only when the soil swarms with larvaj that serious 

 damage is effected. Now, certain crops — for instance, maize and the cereals 

 generally — are but little affected by root-gall. If land l)adly infested be 

 planted with maize, it is reasonable to suppose that the effect will be much 

 the same as if it stood idle and bare ; but, no experiments Jiavin// yet been 

 made, it is impossible to say what value this method may have. Of course, 

 this plan contemplates keeping the land absolutely free of weeds while it is 

 bearing maize. The tough root of maize is not easily penetrated by the 

 worms, and, finding no oilier plant to feed uj)on, they must, it would seem, 

 of necessity starve. 



7. Use of non-infected Soil. — When trees are to be set in infected land they 

 may be filled in with earth taken from a depth of at least 2 feet. Such 



