89 Farmers’ Bulletin 1270. 
Usually these compounds are to be injected into the tree trunk on the theory 
that they will be carried by the sap to all parts of the tree, thereby destroying 
the undesirable parasites. Such injections are without value and may cause 
severe injury (fig. 173). Fruit 
growers would do well to employ 
only the materials and methods 
recommended by their State ex- 
periment station or the United 
States Department of Agricul- 
ture, 
SUN SCALD. 
During very hot periods the 
fruit, particularly that on the 
southwest side of the tree, may 
be heated to such an extent as to 
cause large dark discolorations 
of the skin. Where this trouble 
is prevalent the damage may be 
somewhat reduced by not prun- 
ing the susceptible portion as 
heavily as the rest of the tree. 
The trunks of trees, especially those in young orchards, are sometimes blis- 
tered on the southwest and west sides by the hot afternoon sun. A similar 
type of injury is more commonly produced by severe winter freezing and rapid 
thawing by the afternoon sun. To overcome this trouble trees may be protected 
by shading them with wooden strips driven into the ground rather close to the 
tree. The planting of high-growing cover crops or the intercropping of the 
young orchard with corn or other 
tall crops will also serve to pro- 
tect the trees from too strong 
an exposure during the summer 
season, 
ic. 171.—Apples russeted by Bordeaux mix- 
ture. 
SPRAY MATERIALS.” 
In connection with the control 
of apple insects and diseases, 
many insecticides and fungicides 
have been employed both in an 
experimental way and in actual 
orchard practice. In addition to 
the so-called standard spray ma- 
terials commonly used by com- 
mercial orchardists a very large 
number of proprietary com- 
pounds are now on the market. 
Since the active ingredients of Fie. 172.—Typical lime-sulphur burning on 
the latter are usually made up apple. 
of one or more of the standard 
spray materials, combined with fillers of inert substances, it is obvious that 
there is no particular reason for using them in preference to the standard 
spray materials. As a matter of economy and efficiency, the apple grower 
6 For more complete information on spray materials see United States Department of 
Agriculture Farmers’ Bulletin 908. 
