CONTROL OF CITRUS THRIPS IN CALIFORNIA AND ARIZONA. i 
a shallow brown scab is formed. (Fig. 4.) Where the liquid col- 
lects in large drops it forms a thick, amber-to-black scab which does 
not slough off readily. About 20 per cent of the fruit at picking 
time was thrown into the lowest grade owing to scabbing through 
the use of the weakest resin wash. 
There is only one cheap and effective method of citrus-thrips 
control, viz, the application at high pressure of contact insecticides, 
preferably mixtures containing sulphur in solution. Sulphur mix- 
tures at the proper strength have given uniformly high killing 
results and have thus left no doubt as to their insecticidal power 
over this species. They further show a more or less marked tendency 
to repel the insects and prevent rapid reinfestation of sprayed trees. 
SPRAY MIXTURES AND DILUTIONS. 
Of the large number of combinations of insecticides tested, the 
following have given the best results, and any of the mixtures here 
recommended may be.relied upon to do good work: 
1. Commercial lime-sulphur.—li the lime-sulphur is of a density of 36 degrees on 
the Baumé scale, dilute 1 gallon with 56 gallons of water; if of a density of 33 degrees 
Baumé, dilute 1 gallon with 50 gallons of water. 
2. Sulphur-soda solution.—Two gallons of the stock solution, prepared as described 
on page 8, diluted with 25 gallons of water. 
3. Commercial lime-sulphur and blackleaf tobacco extract (40 per cent nicotine sul- 
phate).—Dilute 1 part of the commercial lime-sulphur, if 34 to 36 degrees Baumé, 
with 86 parts of water; if 30 to 33 degrees Baumé, with 75 parts of water. Then add 
1 part of the tobacco extract to 1,000 parts of the lime-sulphur diluted as above. 
4. Blackleaf tobacco extract (40 per cent nicotine sulphate).—Dilute 1 part with 800 
parts of water. 
COMMERCIAL LIME-SULPHUR. 
The commercial lime-sulphur, diluted with water and without the 
addition of other chemicals, is preferred to any of the other insecti- 
cides because of its cheapness and convenience in mixing. Very 
good grades of lime-sulphur can be purchased in the market at a 
reasonable price, and since the preparation of this product requires 
care and experience, and as it must be made fresh each time or 
special precautions taken to store it in air-tight containers, its home 
manutacture is not advised. When necessary to carry the market 
product over a season it is essential to protect it absolutely from 
the air, asit rapidly loses its insecticidal power when exposed through 
leaky barrels or an open bung. 
SULPHUR-SODA SOLUTION. 
Another mixture contaiming sulphur as the most important ingre- 
dient is made by dissolving sulphur with the aid of caustic soda, 
according to the directions given below. This mixture, though 
