Recent Studies on Peach Yellows and Little Peach 29 



factors need now be considered. The most important of these is 

 girdling or a check to the downward translocation of elaborated plant- 

 food from the leaves toward the roots. This results in the accumu- 

 lation of food above a certain point. Girdling may be accomplished 

 artificially by "ringing" or cutting through the bark and removing a 



Fig. 17 — Rolling of the Leaves Upon Young Peach Tree in Late 

 Summer as a Result of Previous Winter Injury to the Bark of 

 the Main Root Just Below the Collar 



portion, either partly or completely around the stem, branch or trunk. 

 A similar effect is often brought about by label wires, borers, careless 

 cultivation or by weather injuries and stock troubles. A check to 

 growth and sap circulation may be brought about also by scale, brown 

 rot cankers or injurious spray mixtures that cause a hardening or 

 partial killing of the bark at any point. The common forms of win- 

 ter injury which may have the effect of artificial girdling are injury 

 to the wood by low winter temperature and injury to the bark on the 

 main trunk, just at or below the surface of the ground. 



