16 BULLETIN 112, IT. S. DEPARTMENT OF AGEICULTUEE. 



stacks be plowed under or otherwise destroyed late in fall, the aphides 

 harbored thereon will be destroyed. In some cases it may be de- 

 sirable to destroy this vegetation even earlier; that is, before the 

 winter wheat is planted or at least before it makes any growth above 

 ground. Likewise the pasturing of cattle in wheat and oat fields in 

 Oklahoma and Texas during the late fall and early winter is desir- 

 able; indeed, observations made by Messrs. W. E. Pennington and 

 H. S. Smith, of the Cereal and Forage-Crop Insect Investigations, 

 show that where this procedure had been followed, the grain was 

 practically free from the oat aphis, although adjoining unpastured 

 fields showed rather heavy infestation. 



CULTURAL METHODS. 



As in the case of many other grain pests, crop rotation is of much 

 importance in the control of this aphis. "Wheat fields should be 

 located as far from the previous year's grain fields as possible, and 

 especially should they be planted some distance from standing straw 

 stacks. It is also advisable to plant grain as far as possible from 

 apple and other trees, which . harbor the insect during the fall, 

 winter, and spring months. 



SPRAYING. 



Direct applications are hardly practicable in grain fields, but 

 where only small areas are badly infested spraying with blackleaf-40 

 at the rate of 1 part of this insecticide to 900 parts of water, plus 1 

 pound of soap to each 100 gallons of spray liquid, will doubtless 

 prove efficacious, providing the application is thorough. 



Another method which might be adopted in localities where the 

 aphides freely migrate and deposit eggs on apple, is spraying such 

 trees early in spring before the eggs hatch, preferably just pre- 

 vious to their hatching and while the trees are yet in a dormant 

 condition, with commercial lime-sulphur mixture at the rate of 1 part 

 of the mixture to 8 parts of water. 



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