66 MASS. EXPERIMENT STATION BULLETIN 449 



any material manufactured in the leaves. Spy 227 stock budded to strain R 

 buds which were sheared off in November died in typical fashion the next sum- 

 mer. Although the trouble appears to be caused by a virus there is no evidence 

 that it can be transmitted except by budding. New combinations of varieties 

 or strains budded on Spy 227 reveal that Red Spy, Foster Gravenstein, Whit- 

 comb Gravenstein, Mead Gravenstein, Rhode Island Greening, Baldwin, and 

 Galbraith Baldwin all died in typical fashion; while Northern Spy, Milton, Ken- 

 dall, Early Mcintosh, and Macoun made normal growth. A paper will be 

 published in the Proceedings of the American Society for Horticultural Science, 



Magnesium Deficiency in Massachusetts Apple Orchards. (W. D. Weeks.) 

 Leaf samples for chemical analysis were taken again during 1947. Analyses of 

 the 1946 samples indicate that mature apple trees which had received 30 and 60 

 pounds of magnesium sulfate per tree did not have their magnesium content 

 increased appreciably over check trees. The low magnesium content of the 

 leaves of the 1946 samples indicates that many of these trees were deficient in 

 magnesium but they failed to show any typical deficiency symptoms during the 

 growing season. Analysis of the 1947 samples is not complete at this time so 

 we do not know whether heavy soil applications of magnesium sulfate have 

 been successful in increasing the magnesium content of mature apple trees. No 

 typical magnesium deficiency symptoms were observed on these trees during 

 the 1947 season. 



Influence of Chemical Treatments on Flowering and Fruiting of Fruit Trees- 



(F. W. Southwick and W. D. Weeks.) Chemical thinning tests were conducted 

 at Amherst and in three commercial apple orchards using the dinitro materials 

 (DN^l and Elgetol) at blossom time and the sodium salt of naphthaleneacetic 

 acid (App-L-Set) at calyx time and two and four weeks after calyx. One test 

 on Halehaven peaches was conducted using three dinitro materials (DN^l, 

 DN^289, and Elgetol) at blossom time. 



Although the bloom was heavy, the weather, except for the first two or three 

 days when apple flowers commenced to open, was not conducive to a heavy set. 

 During the bulk of the blooming period cool, rainy weather limited the extent 

 of pollination. Under these conditions the set was not nearly as great as the 

 bloom indicated it might be. Elgetol applied to Red Astrachan, Baldwin, and 

 Duchess resulted in much more thinning and foliage injury than similar single or 

 double applications of DN^l. Where the set was heavy enough to warrant 

 thinning on Yellow Transparent, Wealthy, Duchess, and Early Mcintosh, DNffl 

 gave satisfactory results. It no longer seems desirable to consider the liquid dini- 

 tro materials for blossom thinning of apples. In the peach test DN^289 reduced 

 the set more than equivalent concentrations of either DN^l or Elgetol. 



Applications of 8 ounces of App-L-Set per 100 gallons of spray at calyx time 

 eliminated the crop on Duchess apple trees and resulted in severe leaf dwarfing 

 and distortion. Calyx applications of this material to Wealthy, Mcintosh, and 

 in some instances Early Mcintosh, thinned satisfactorily at calyx time with 

 much less foliage injury. App-L-Set appears to be more injurious to apple foli- 

 age when applied shortly after bloom than when used at the same or higher 

 concentrations two and four weeks after calyx. Tests at Amherst and in one 

 grower's orchard, using up to 16 and 20 ounces of App-L-Set per 100 gallons of 

 spray four weeks after calyx on Mcintosh, Golden Delicious, and Early Mcintosh, 

 show that chemical thinning can be accomplished at this late date. A treatment 

 that can be made as late as four weeks after calyx has a distinct advantage over 

 bloom or calyx applications, since the extent of fruit setting and the necessity 

 for thinning can be rather accurately determined by that time. Of course, the 



