VIII CONTENTS. 



Page. 



The chemicals in fumigation 40 



Potassium cyanid (KCN) 40 



Sulphuric acid (H 2 S0 4 ) 41 



The amount of sulphuric acid necessary 42 



Water as a factor in fumigation 44 



The effect of different proportions of water 45 



On temperature of gas 45 



On amount of available gas 45 



The correct proportion of water 47 



The most economical proportion of chemicals to use 47 



The amount of chemicals in very small dosages 48 



Mixing the chemicals 48 



Effect of the presence of sodium chlorid on the amount of gas given off 49 



Nature of the residue 50 



Dosages for various scale pests 51 



Factors which affect the dosage : 52 



The purple scale 53 



Length of exposure 55 



Eradication 55 



Difficulty of destroying the scale on the fruit 56 



Two successive treatments 57 



The red scale 57 



The black scale 59 



The yellow scale 60 



Dosages in general fumigation ; 61 



Time of the year for fumigation 61 



Fumigation for the mealy-bug 63 



Fumigation during the blossoming period 64 



Fumigation while the fruit is of small size 65 



Fumigating lemons 65 



Effects of fumigation on unhealthy trees 66 



Greater susceptibility to injury of some varieties than others 67 



The distribution of gas within a tent 67 



Fumigation for physiological effects 67 



Effects of meteorological elements on fumigation 68 



Moisture 68 



Temperature 69 



Light 71 



Winds 72 



Injury to sprayed trees 72 



The appearance of fumigated trees 73 



The presence of old scales on fumigated trees 74 



A device for covering fumigation generators 74 



The effect of climatic conditions on scale insects 76 



The effect of fumigation on ladybirds (Coccinellidse) and Scutellista cyanea 



Motsch 77 



The cost of fumigation 78 



General cautions 80 



List of the writer's published articles and addresses on the fumigation 



investigation in California 81 



