DETERMINE INJURY FROM COLD WEATHER 157 



from which the cambium has been removed only in part may 

 be painted with vv^hite lead and oil or coated with wax. 



5. Determine Injury from Cold Weather. Although many 

 different factors affect the distribution of the fruit industry, 

 probably the greatest single factor has been winter tempera- 

 tures. Minimum temperatures in different sections of the 

 country have determined the kinds of fruit that can be 

 grown in such sections. In addition, an occasional winter 

 of unusually low tem- 

 peratures is experi- 

 enced in a section 

 where certain fruits 

 normally thrive and a 

 large portion of the 

 trees are seriously in- 

 jured or killed, caus- 

 ing large financial 

 losses. Injury occurs 

 to various parts of the 

 tree such as: (a) wood 

 tissues, (6) leaf and 

 fruit buds, (c) blos- 

 soms, {d) roots. 



(a) Injury of 

 Wood Tissues, The 

 different tissues with- 

 in the same plant 

 vary considerably in 



their responses to low temperatures. In well-hardened wood, 

 pith is usually the least-resistant tissue, followed in order by 

 sap wood, bark, and finally cambium, which is usually the 

 most resistant. 



Wood injury occurs iii many different forms such as: (1) 

 black heart, (2) crotch injury, (3) crown or collar injury, (4) 

 sun scald, (5) splitting of the trunk, and (6) killing back 

 of the twigs and young branches. 



(Mich. Exp. Station) 



Fig. 55. Cross and longitudinal sections of 

 apple wood showing "black heart" injury. 



