13 - 



Weak points 



1. Trees need support because of brittleness of roots. 



2. Attractive to mice. 



3. Extremely susceptible to fire blight (Sec.)^ 



4. Susceptible to woolly apple aphids (Sec.)^ 



5. Requires deep, well-drained soils and detailed tree management. There- 

 fore, M9 generally is not recommended in Massachusetts, 



Interstem trees (M9/HM106 or M9/MM111) 



Strong points : 



1. Small trees - approximately the size of M26. 



2. Better anchorage than trees on M9 or M27, 



3. Early bearing but only if good trees are received from the nursery and 

 the trees grow vigorously in the orchard. 



Weak points : 



1. More expensive to buy. 



2. Usually only available by contracting 2 years in advance. 



3. It is difficult to develop strong central leaders on some varieties and 

 spur strains when on interstems. Thus, leader support may be necessary. 



4. Suckers from rootstock particularly when the interstem is planted above 

 ground. 



5. The interstem portion is generally M9 and mice like the bark of M9. 



6. Burrknots on the M9 stempiece may be the site of insect and disease 

 problems. 



1. Trees not as well anchored as those on MMUl or MM106. 

 8. Trees require detailed tree management. 



M26 



Strong points : 



1. Smaller tree than those on M7A thus easier to prune and harvest. 



2. 45 to 60% dwarfing of seedling tree. 



3. Early bearing in some orchards. 



4. Very productive per acre if properly spaced, trees vigorous, and leaders 

 supported when necessary. 



5. Tolerance to low temperature. 



Weak points : 



1. Extremely susceptible to fire blight (Sec.)l 



2. Susceptible to woolly apple aphids (Sec.)^ 



3. Susceptible to collar rot. 



