INSECTICIDES AND EQUIPMENT FOR CONTROLLING INSECTS 17 
Caution.—Lead arsenate is a very poisonous compound and 
should be stored in plainly labeled containers away from all food 
products. 
Both lead and arsenic residues on treated plants are poisonous. The 
Federal tolerance for lead on apples and pears is 0.05 grain per 
pound and for arsenic it is 0.025 grain of As,O; per pound of fruit. 
LEAD ARSENATE (BASIC) 
Chemically, basic lead arsenate is lead hydroxy arsenate 
(Pb.(PbOH) (AsO,);). It should contain the equivalent of about 
28 percent of total arsenic pentoxide (As,O;) and less water-soluble 
arsenic than the equivalent of 0.5 percent of arsenic pentoxide. 
Like the much more commonly used acid lead arsenate, this ma- 
terial is a white powder which is colored pink when marketed as an 
insecticide to denote that it is a poison. Its use is virtually limited 
to particular areas on the Pacific coast and in eastern peach orchards, 
for certain chewing insects, where acid lead arsenate causes plant 
injury. It is less effective in controlling insects than is the acid 
form. Normally it is used at a rate of about 4 to 6 pounds to 100 
gallons of water. 
Caution.—Like acid lead arsenate, this material is toxic to man 
and higher animals, and should be stored in a safe place in clearly 
labeled packages. 
The spray-residue tolerances for acid lead arsenate, as given above, 
apply also to basic lead arsenate. 
LIQUID LIME-SULFUR AND DRY LIME-SULFUR 
As the name implies, lime-sulfur is made from lime and sulfur. 
A complex mixture containing principally calcium polysulfides, it 
may be purchased in concentrated solution or as a dry powder, or 
it may be made on the farm. It is marketed in concentrated form 
as a deep amber-colored liquid, or as a yellow-orange powder. It 
is applied in the dilute form and is ill-smelling and irritating to the 
user. 
Liquid lime-sulfur is used chiefly as a scalicide and a fungicide on 
fruit trees and woody shrubs. It is used extensively for the contro] 
of the potato psyllid in the Western States and is also valuable for 
the control of the peach twig borer, pear psylla, and pear leaf blister 
mite. As a scalicide it has been displaced in some localities by lubri- 
cating-oil sprays. When used in the dormant season to control scale 
insects it is applied at a strength of 10 to 14 gallons of the liquid 
concentrate in 100 gallons of spray. Asa fungicide and asa spray for 
the common red spider and some other mites on plant foliage it is 
usually diluted to a strength of 2 gallons in 100 gallons of spray. 
For control of the cyclamen mite on chrysanthemums and snap- 
dragons, a lime-sulfur spray consisting of 1 to 2 quarts to 100 gallons 
of water with the addition of 34 pint (114 cupfuls) of a spreader— 
sodium oleyl sulfate containing a synthetic resinous sticker—has 
proved effective. This spray has the advantage of not staining the 
foliage as does lime-sulfur solution without the spreader. 
For some purposes dry lime-sulfur may be substituted for liquid 
lime-sulfur at the rate of 4 pounds for 1 gallon of the liquid. On 
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