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"Y^'ESTBRI':" LEAD ARSENATE 



The unprecedented change-over from lead arsenate to DDT for the control of 

 codling moth in the Pacific Nortliwest apparently has created a surplus of lead 

 arsenate in that area. At least some of it has been made available in the East 

 at some advantage to the consumer. Questions have been raised concerning the 

 safeness and effectiveness of this western lead under our eastern conditions. 

 Here are the- ansv/ers that we have been able to gather at this writing. 



Letters to Professor l/hitcomb and me from state, federal and commercial 

 entomologists v;ho have worked with the several forms of western lead arsenate 

 have provided the material upon v^rhich this report is based. 



Form ; ITestern lead arsenate is produced in two forms. One, the so-called 

 amorphous type, consists of irregular particles in a variety of shapes. These 

 may or may not be ground to finer sizes but the result is a powdery material similar 

 to the standard acid lead arsenate well known already here in the East, The second 

 type, known as flat or crystallne (platelet) lead arsenate differs from the stan- 

 dard type in the shape of the particles. They are flattened, irregular discs, a 

 characteristic v.'hich con be seen under a microscope or good hand lens. 



Relative Merits ; There is some indication,t not supported by all investigators, 

 that the flat lead arsenate adhered to th.e foliage and fruit better than does the 

 standard, amorphous form. Apparently the discs come to lie like shingles and thus 

 form a more complete coverin^^. It is the opinion of those contacted that conditions 

 hers in the East should not materially change the effectiveness of the flat-type 

 lead arsenate nor make it less effective than the standard type, 



Safeness: The relative safeness of the western and eastern loads should not 

 differ^! Both are required by lav/ to contain not mors than 0,75 per cent soluble 

 arsenic. In view of this, no one can foresee any reason for believing that western 

 leads of either form should be any more injurious to trees in the East than the 

 standard lead arsenates used in the past. 



Combination with other materials- There is the possibility that the addition 

 of oil-type stickers and sane other materials might cause a flocculation in the 

 spray tank which would decrease the value of the flat-type lead if it has any 

 advantage. In Llassachusetts, where pests are severe enough to require the addition 

 of an oil-tTy'pe sticker, it is probable that DDT will be added to the lead arsenate, 

 Vihere this is done no sticker need be included, 



— Ellsworth H. 1';Tieeler 



VaiAT KII>ro OF SPRAY- OIL? 



As a fruit grower, do you take better care of the motor in your car or 

 tractor than you do the treos which provide your income? How do you buy oil for 

 your motors? liost of you probably have a good reliable and favorite brand. You 

 also know what viscosity or S,A.E, number is best f<Ji- the particular engine. And, 

 when asked v/hether you vjant a 30 or 35 cent oil, you always say "The best, of 



course". 



How about spray-oils for your trees?. Here again, specifications vary and so 

 do prices. But do you knov/ v;hat characteristics in a spray-oil are desirable? Do 

 you always choose the higher priced ones? Tlicse points can be important to you as 

 a fruit grov;er. Spray-oils are not all alike* They differ in their effectiveness 

 and in thoir safeness on your trees. 



