16 BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE. 
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. TV. 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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