4 - 



stunted trees fruit early and fail to produce adequate vegetative 

 growth for ample bearing surface. 



Many orchardists are now planting trees on M 26, about which 

 we have little experience or knowledge. There is also much renewed 

 interest in M.7 budded higher than in older plantings on this root- 

 stock, to enable deep planting for better anchorage. 



MSU has developed several new apple rootstocks from seed of 

 open pollinated trees of the Mailing 1 through 16, Alnarp 2 and 

 Robusta 5. These have been named the MAC (Michigan Apple Clone) 

 series. The more dwarfing, well-anchored clones are MAC 1,4,9,10, 

 25,39 and 46. MAC 9 is the most dwarfing, producing trees slightly 

 larger than M.9 but with better anchorage. Trees on these root- 

 stocks will soon be under evaluation in commercial orchards. 



Research and grower experience with apple trees on clonal 

 rootstocks indicates such plantings should be placed on the most 

 desirable fruit sites. Because the trees are smaller, bloom is 

 much more susceptible to frost injury. 



Orchardists have learned that trees on clonal rootstocks re- 

 quire excellent management practices if tree performance is to 

 equal grower expectations. This includes site selection, soil 

 preparation, planting techniques, weed control, soil and moisture 

 management and early training. Some growers have erred and planted 

 trees too close together, resulting in crowding before trees begin 

 to produce fruit. This has prompted interest in transplanting of 

 established trees and in summer pruning. 



Frost Control 



High density plantings on size-control rootstocks have accen- 

 tuated the concern for ideal planting sites for apple orchards be- 

 cause the smaller tree is much more vulnerable to spring frosts. 

 Growers with less than ideal sites often find it necessary to con- 

 sider some method of frost control in high-density plantings. 

 Frost protection with oil and propane gas has become very expensive. 

 Overtree sprinkling has been demonstrated to be an effective way 

 of preventing frost injury. This technique along with wind machines 

 and helicopters, may become more popular in the future with orchard- 

 ists requiring occasional frost protection. Research with a foliar 

 application of rhizobitoxin suggests it may delay bloom several 

 days to minimize frost injury. 



Tree Management 



Spur-type Delicious are very popular in both clonal and seed- 

 ling rootstock plantings. Unfortunately, these trees have not al- 

 ways performed to grower expectation. The primary cause for disap- 

 pointment probatly has been management rather than rootstock, tree 

 density, or a choice of strain. 



