ORCHARD TXSECTS OF THE PACIFIC NORTHWEST 67 



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 insec- 

 ticide 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 msecticide unless it 

 is properly 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, 



Ficcre 81.— Woolly apple aphids parasitized by Aphelinus mali. 



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

 is usually sold in the form of a fluffy powder, in which form it can be 

 handled and stored readily, if kept dry. The quantities recommended 

 in this circular are for the powdered lead arsenate; if paste is used, 

 the quantities should be doubled, since the paste form usually contains 

 50 percent of water. Lead arsenate may be combined with oil emul- 

 sions, with nicotine solutions, and with lime-sulphur or bordeaux 

 mixture for controlling various insect pests and fungous diseases at 

 the same time. If lead arsenate is combined with lime-sulphur solu- 

 tion, the mixture should be used at once, on account of a chemical 

 reaction which occurs. This reaction may be retarded by putting 

 casein spreader or hydrated lime into the tank first, at the rate of 1 

 pound to 100 gallons of spray. If anv residue of arsenic or lead on 

 the harvested fruit exceeds the tolerance permitted by the Federal 

 Food and Drug Administration, it must be removed by washing or 

 wiping before the fruit is sold. On account of the restrictions on the 

 presence of lead on fruit that are contemplated, it may be necessary in 

 some cases to substitute arsenicals not containing lead, although these 

 materials have not been as effective or as safe as the lead arsenate. 



FLUORINE COMPOUNDS 



Under some conditions certain fluorine compounds may be used to 

 replace lead arsenate in spray schedules for the codling moth. This 

 is explained on page 7. 



