xvi CONTENTS 



CHAPTER XVII 



PAGE 



INSECTICIDES AND FUNGICIDES (continued) . . . 164 



Alkaline Washes 



The terms, soda and potash ; no reason for using a mixture of 

 the two; changes undergone by soda after spraying; effect 

 of rain falling after the spraying; insecticidal value of alkalis 

 increased by addition of paraffin ; not so their detergent 

 value ; the strength of alkali required ; relative efficiency of 

 lime and soda ; attempts to improve the adhesiveness of alkaline 

 washes. Lead arsenate; differences in its character when 

 prepared from different reagents; its use with other spray 

 substances; calcium arsenate. 



CHAPTER XVIII 



INSECTICIDES AND FUNGICIDES (continued) . . . 172 



Copper Fungicides 



Origin of Bordeaux mixture; the basic sulphates of copper; 

 necessity of the presence of soluble copper for fungicidal action ; 

 action of air on Bordeaux mixture ; soluble fungicides ; libera- 

 tion of soluble copper from the basic sulphates ; bulkiness of 

 the different basic sulphates; Bordeaux paste; relative 

 efficiency of Bordeaux mixture and paste ; their relative 

 adhesiveness, and that of Burgundy mixture; methods of 

 preparing and testing Bordeaux mixture ; changes undergone 

 by it on keeping; bulkiness of it dependent on the manner of 

 mixing; Bordeaux mixture and treacle; alkaline and solid 

 copper fungicides. Burgundy mixture; proper proportions 

 of the ingredients; scorching produced by the mixture; 

 change undergone by it on keeping. 



CHAPTER XIX 



INSECTICIDES AND FUNGICIDES (continued) . . .186 



The Fungicidal and Scorching action of Copper 

 American work on fungicidal action ; its dependence on the 

 amount of copper in solution, and not on the nature of the 

 compound ; the question of excretions from the fungus ; entry 

 of copper into the leaf of the plant ; the effect of copper on 

 plant growth; the effect of copper spraying on soil-fertility. 

 Copper injury; unavoidable in many cases; American work 

 on the subject; connection between fungicidal and scorching 

 action; experiments on scorching action; " natural " scorch- 

 ing; preservative effect of copper; variation of scorching and 

 fungicidal action with the strength of the substances ; action 

 of lime ; effect of the presence of neutral salts ; action of 

 electro-negative copper; the wetting of the leaves by the 

 fungicide ; action of saponin. 



