CONTENTS 
Page. 
Fumigation of citrus trees. R. S. Woglum. . 1 
Historical 1 
Recent renewal of interest in fumigation in California 2 
Extent to which fumigation is practiced in California 3 
The various systems of fumigation 4 
By contract 4 
By associations 5 
By counties 5 
By private individuals 5 
Extent and character of citrus orchards 6 
Insect enemies of citrus fruits 7 
The purple scale (Lepidosaphes beckii Newm.) > 8 
The black scale (Saissetia oleae Bern.) • 8 
The red scale {Chrysomphalus aurantii Mask.) 9 
The yellow scale ( Chrysomphalus citrinus Coq.) 10 
The mealy-bug (Pseudococcus citri Risso) 10 
Apparatus 10 
Tents 10 
Poles and derricks 20 
The McFadden machine 21 
Supply cart and supply wagon. .'. 22 
Generating vessels 24 
General procedure 24 
Calculating the dosage , 27 
Securing the measurements around and over 28 
The old method of procedure 30 
An improved system of fumigation 32 
Leakage of gas 33 
Dosage schedule 34 
Procedure 37 
Advantages under this system 37 
Experience with this system 38 
The chemicals in fumigation 40 
Potassium cyanid (KCN) 40 
Sulphuric acid (H 2 S0 4 ) 41 
Water as a factor in fumigation 44 
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 
The red scale 57 
The black scale 59 
The yellow scale 60 
Dosages in general fumigation 61 
i The three papers constituting this bulletin were issued, the first on May 13, 1911, and the last two on 
May 10, 1911. 
VII 
