70 CIRCULAR 2 7 0, XI. S. DEPARTMENT OF AGRICULTURE 



destroy many of the beneficial insects. However, since the adults 

 usually are not harmed, being able to avoid the spray, they are able 

 to return, and they or their young may rapidly complete the destruc- 

 tion of the pests which has not been entirely accomplished with the 

 insecticides. 



SPRAY MATERIALS 



Fortunately, most of the insect pests of fruit trees spend at least 

 part of their lives in situations that enable the fruit grower to control 

 them by means of sprays. Annual crops may often be protected from 

 serious insect injury by following certain practices of planting, 

 harvesting, cultivating, and crop rotation, but with fruit trees these 

 methods are usually out of the question. Spraying is expensive, but 

 its cost is small as compared with the value of the crop. 



Insects feed in two distinct ways. Some bite off and swallow por- 

 tions of the fruit or foliage. Many of these biting insects may be de- 

 stroyed by keeping the trees covered with a poisonous material which 

 the insects eat with their food. The young of the codling moth and 

 other moths, beetles, sawflies, grasshoppers, and crickets are examples 

 of biting insects. Other insects have mouths in the form of a sucking 

 apparatus which they insert into the plant tissue and through which 

 they draw out the plant juices. These insects are not affected by 

 stomach poisons placed on the surface of the leaves or fruit, and it is 

 not possible to poison the plant juices without injuring or killing the 

 plants; therefore materials known as contact insecticides are used for 

 their control. These materials poison the insects through their 

 breathing pores, or by a corrosive action on their bodies. The scale 

 insects, aphids, leafhoppers, treehoppers, and the true bugs are 

 examples of sucking insects. Red spiders also feed in this manner, 

 although they are not true insects. 



Several spray materials have been employed so extensively and suc- 

 cessfully that they have become standard insecticides. The worth 

 of others has not yet been proven, although they may already be used 

 to some extent. As a rule the fruit grower will find that the standard 

 materials, with known ingredients, are more economical and effective 

 than similar proprietary compounds. Compounds whose ingredients 

 are unknown should be avoided, as they are too often worthless. The 

 Federal insecticide act of 1910 specifies that if any insecticide shipped 

 from one State to another contains arsenic in any form, the total 

 amount of arsenic must be stated on the label ; and that if the insecti- 

 cide contains any inert ingredients, the names and amounts of each 

 shall be stated; or the names and amounts of the active ingredients 

 may be stated together with the total amount of inert ingredients. 

 The various States in the Pacific Northwest have similar laws govern- 

 ing the sale of insecticides within them. Growers should therefore 

 refuse to buy any material offered for sale as an insecticide unless it 

 is property labeled. 



Lead Arsenate 



There is no more effective insecticide for chewing or biting insects 

 than acid lead arsenate. It is a somewhat slow-acting poison, but it 

 adheres more firmly to the fruit and foliage than do other materials, 

 and is therefore effective for some time after it has been applied. The 

 quantities recommended in this circular are for the powdered lead 



