362 Fruit-growing in Arid Regions 



however, that the alkali salt solutions, which are abundant in all 

 arid soils, are solvents of arsenic and so are constantly bringing 

 this extremely poisonous material into solution. This action is 

 of course greater in some soils than in others, depending on the 

 constituents present. 



This condition is indeed serious. We have no poison other 

 than the arsenic preparation with which the codlin-moth may be 

 successfully combated, and if we are to grow apples and pears 

 successfully, spraying cannot be dispensed with. In the bulletin 

 mentioned above Dr. Headden sums up the situation as follows : 



" I have no remedy to suggest for either condition. Preven- 

 tive measures are, so far as I can see, our only recourse. Those 

 which suggest themselves to me are: to remove the arsenic-laden 

 soil from about the crown of the tree and replace it with fresh 

 soil; to use standard brands of lead arsenate in preference to the 

 arsenite of lime or white arsenic,' sal soda, and lime; to use as 

 little lead arsenate as possible. I have been told that good re- 

 sults have been obtained by using 2 and even 2 pounds of pasty 

 lead arsenate to 100 gallons of water, but the spraying must be 

 done thoroughly. Spray no oftener than is absolutely necessary. 

 If I am not mistaken, Professor Gillette has found that 95 per 

 cent of the effect of the whole season's spraying was obtained 

 by the first spraying when thoroughly well done. Some device 

 should be used to prevent the spray material from running down 

 the trunk and collecting at its base, or it would be still better to 

 make provision for gathering the whole of the drip. Water rich 

 in alkalies should not be allowed to flow close enough to the tree 

 to permit of the deposition of the alkalies in the soil about the 

 trunk of the tree. Concentrated lye, if used to kill woolly aphis, 

 should not be applied to the soil at the crown of the tree or per- 

 mitted to flow down and collect there." 



Insect Enemies of Apple 



Green Apple Aphis (Aphis pomi). This is the common green 

 louse that curls the leaves of the apple tree. While primarily a 

 leaf-feeder, this louse also attacks the tender tips of growing 

 shoots, especially grafts and watersprouts. This insect ranks 



