- 8 - 



2. Varney, E. H., J. N. Moore, and D. II. Scott. I960. Field resistance of 29 

 additional strawberry varieties and selections to Vert ici Ilium. Plant 

 Disease Reporter 44:370-371. 



James F. Anderson 



I I I I I I I I I I I I I I I I 



SIZE-CONTROLLING APPLE ROOTSTOCKS 



At the symposium on Size-Controlling Apple Rootstocks held at the University 

 of Connecticut, Karl D. Brase, Geneva Experiment Station, discussed "Points That 

 Must Receive Attention Xvhen Propagating and Planting Apple Varieties on Size- 

 Controlling Clonal Rootstocks". 



Brase classified size-controlling apple rootstocks into four groups: 

 (1) stocks having strong dwarfing effect - E.ll. (East Mailing) VIII, E.M. IX, 

 E.M. XX, and E.M. ]CiI; (2) stocks that cause a semi-dwarfing growth of the 

 variety - E.M. VII, M.M. (Malling-Kerton) 106, E.M. II, and possibly M.M. ill; 

 (3) stocks that cause vigorous grovjth of the variety - E.M. I, E.M. IV, E.M. XI, 

 M.M. 104, M.M. 109, and A2; and (4) stocks that cause very strong growth of the 

 variety - E.M. XII, E.M. XIII, E.M. XV, E.M. XVI, and E.M. XXV. 



At the present time, only E.M. II and E.M. VII are recommended for commer- 

 cial orchards in Massachusetts vrith E.M. VII being the main size-controlling 

 rootstock used. E.M. IX has been recommended only for the backyard gardener. 

 The M.M. (Malling-Merton) group needs further testing. 



E.M. IX - Brase stated that E.M. IX, v/hich has very brittle roots, can be grown 

 without being supported provided they are properly constructed and planted. 

 Deeper planting is possible by having a longer rootstock portion. 



E.M. IX requires a deep well-drained soil and mature trees on this stock are 

 no larger than one-quarter of the same variety on a seedling rootstock. E.M. IX 

 can be used as an interstock between a standard rootstock and the scion variety. 

 Trees constructed this way are larger than when E.M. IX is used as the rootstock 

 being at maturity about one-third the size of standard trees of the same variety. 



"The strong dwarfing effect of the E.M. IX clonal rootstock is not, as some 

 believe, due to a shallow and limited root system, but rather to genetic char- 

 acteristics; namely, the thick bark of roots and trunk that limits nutrient 

 conduction from the soil but favors a storage of carbohydrates produced by the 

 leaves." 



E.M. VII - One and two-year old trees on E.M. VII have thin roots which tend to 

 grow downward and if planted too shallow start leaning before stronger roots can 

 develop. "If planted shallow there is also a tendency to produce abundant sucker 

 growth from the root system. For these reasons, particular care must be taken to 

 bud the variety to E.M. VII high enough so that on transplanting to the orchard 

 deeper planting is possible but still have the varietal rootstock graft union just 

 above soil level. Deeper planting will prevent leaning and also suppress sucker 

 growth from the root system. But, even if the tree is planted deeper, care also 



