12 BULLETIN 787, U. S. DEPARTMENT OF AGRICULTURE. 
not be necessary after the trees reach 6 inches in diameter or such a 
size that they are immune from attack. Isolated trees, however, are 
sometimes exceptions to this and should be watched. 
Many spray solutions have been tried by the writer, but by far the 
most successful has been the combination of a soluble arsenate with 
an oil emulsion. This provides a penetrative poison which enters 
the exudation pores made by the larva? through the bark and poisons 
the inner bark on which the young larva? feed. Insoluble arsenates 
are not so effective, as the exudation pore is usually plugged with a 
wad of fine granular frass from which the arsenate in suspension 
filters out. Kerosene emulsion can be used to carry the arsenical, but 
it has been found that the miscible oils are just as satisfactory and 
require much less time in preparation. 
The formula and preparation are as follows: 
Dissolve i pound of sodium arsenite or arsenate in 5 gallons of water. Add 
1 quart of miscible oil and agitate thoroughly. 
With kerosene emulsion, dissolve \ pound of the arsenical in 4 gallons of 
water and add 1 gallon of stock solution of kerosene emulsion, agitating 
thoroughly. 
LITERATURE CITED. 1 
(1) Deasbobn, H. A. S. 1821. Locust trees. In Mass. Agric. Repos. and 
Journ., v. 6, p. 270-275. 
(2) Pickering, T. 1821. Colonel Pickering on the locust tree. In Mass. 
Agric. Repos. and Journ., v. 6, p. 360-362. 
(3) Schwaez, E. A. 1891. Coleoptera on black locust (Robinia pseudacacia). 
In Proc. Ent. Soc. Wash., v. 2, p. 75. 
(4) Kellogg, R. S. 1904. Forest planting in western Kansas. U. S. Dept. 
Agr., Bur. Forestry Bui. 52, p. 43. 
(5) Cotton, E. C. 1906. The insects affecting the black locust and hardy 
catalpa. Ohio Dept. Agr., Div. Nursery and Orchard Inspection Bui. 
Xo. 7, p. 8-12. 
(6) Hopkins, A. D. 1907. Some insects injurious to forests: Additional 
data on the locust borer. U. S. Dept. Agr., Bur. Ent. Bui. 58, Part III. 
(7) Gagman, H. 1915. The locust borer (Cyllene robinise) and other insect 
enemies of the black locust. In Second Biennial Report of the State 
Forester of Kentucky, p. 32-33. 
1 Other papers dealing with the locust borer will be found in the bibliography given by 
Dr. A. D. Hopkins in the bulletin entitled " Some insects injurious to forests : The locust 
borer." (TJ. S. Dept. Agr., Bur. Ent. Bui. 58, pt. I.) 
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