6- 



in 1978 to confirm that the problem was K deficiency rather than 



CaClo burn, 



B Deficiency of Pear 



Occasionally B defic- 

 iency is so acute in pear 

 trees that the fruits be- 

 come malformed and cracked 

 (Figure 3) . Soil appli- 

 cations of 13 at the rate 

 suggested for apples is 

 effective for preventing 

 a shortage of this element 

 in pear trees. 



******************** 



FURTHER OBSERVATIONS OF TREE PERFORMANCE ON M.26 



William J. Lord 

 Department of Plant and Soil Sciences 



The 1976 Apple Tree Survey indicated that 8% of the trees 

 in Massachusetts on size-controlling rootstocks are on M.26. Thus, 

 this rootstock is common enough for us to observe its performance 

 under a wide variety of soil and cultural conditions. 



Trees on M.26 react more to unfavorable growing conditions 

 than those on more vigorous size-controlling rootstocks. Trees 

 within a block may be extremely variable in vigor, with some of 

 them being weak and/or difficult to train (assuming all the trees 

 are on M.26). Spur-type trees appear weak when planted on light 

 soils (Figure 1) , and so do Cortland trees on this rootstock. 



The leaders of trees on M.26 often are "droopy" on non-bearing 

 trees, and these trees tend to lean more frequently than trees on 

 other rootstocks (Figure 2) . We suggest providing support for the 

 more troublesome trees rather than trying to correct the problem 

 with severe pruning. The objective is to maintain a central leader 

 until the desired tree height is obtained. 



