6 MISC. PUB. 526, U. S. DEPT. OF AGRICULTURE 
Mexican bean beetle, when used at the rate of 6 pounds to 100 gallons of 
water, it is of more value against flea beetles and blister beetles. It 
may cause foliage injury. To reduce foliage injury, alkaline waters 
and those containing sulfates should not be used with this material. 
Caution.—Barium fluosilicate is very poisonous to higher ani- 
mals and man. Observe care in its use. For spray-residue 
tolerance see page 3. 
BENTONITE 
Bentonite is a naturally occurring, light-colored clay. Chemically, 
it is chiefly a hydrous silicate of aluminum, calcium, and magnesium ; 
but a variety of other compounds may be present, depending upon the 
source of the material. 
There are two general classes of bentonites, the swelling and the 
nonswelling. ‘The former is used to dilute insecticidal and fungicidal 
dusts, as an emulsifier for home-mixed oil emulsions, and in the prepa- 
ration of tank-mixed and proprietary nicotine bentonite sprays. 
The principal source of the swelling type is the Black Hills region 
of Wyoming and South Dakota, and the name “Wyoming bentonite” 
is generally used to distinguish it from nonswelling clays. When wet 
it will absorb water and swell to from 7 to 11 times its dry volume, 
forming a gelatinous mass. 
Other bentonites which absorb water and swell to not more than 2 or 
3 times their dry volume are mined in Arkansas, California, Georgia, 
and Mississippi. 
Most of the swelling types of bentonites will react with nicotine 
to form a nicotine bentonite in which part of the nicotine is insoluble 
in water, so that the combination acts as a stomach poison rather than 
a fumigant or contact insecticide. At present Wyoming bentonite is 
preferred for use with most insecticides, although certain of the low- 
swelling types from Mississippi have recently come into use. These 
are obtainable as a fine powder, while the Wyoming bentonites may 
be obtained either in powder form, which is preferred when used as a 
diluent, or in pellets for use in making tank-mixed oil emulsions or 
nicotine bentonite sprays. (See Nicotine Bentonite, p. 24, also 
Mineral Oil, p. 20.) 
BETA NAPHTHOL 
Beta naphthol (C,,H;OH) is a slowly volatile, crystalline compound 
that is used to impregnate corrugated paper bands, for placing around 
the trunks of mature apple trees to trap and kill codling moth larvae. 
Rolls of single-faced corrugated paper 2 inches wide may be dipped 
in a hot (250° F.) solution of 1 pound of beta naphthol (technical) 
in 1.5 pints of lubricating oil having a Saybolt viscosity of 100-300 
seconds at 100° F. The mixture can be used cold if diluted with gaso- 
line. The chemical coating should be from 0.3 to 0.5 ounce of beta 
naphthol plus oil per linear foot of band, the smaller quantity being 
used in the Pacific Northwest. 
Some persons with delicate skin are very sensitive to beta naph- 
thol and may experience a burning sensation when working with it, 
but the effect is only temporary. Gloves may be worn to avoid this. 
Prepared bands may be purchased in 250-foot rolls. 
BORDEAUX MIXTURE 
Bordeaux mixture is the name applied to sprays made by reacting 
dilute solutions of copper sulfate (bluestone) with lime. Home-made 
