ANNUAL REPORT, 1945-46 61 



important element, nitrogen. No evidence of a deficiency of other than these 

 six elements has yet been found in Massachusetts orchards. The value to the 

 trees of some of these elements may be indirect in that they favor the growth of 

 grass or cover crops and thus add humus and colloidal matter to the soil to bene- 

 fit the trees. 



A complete fertilizer and magnesium and boron may not be needed every year, 

 as is nitrogen, but should be applied from time to time as orchard needs require. 

 Magnesium limestone should always be used rather than a high calcium limestone 

 when soil acidity drops below about pH 5.50. Boron in the form of borax should 

 be applied to orchards that have shown deficiency, every 3 or 4 years at the rate 

 of 30 to 50 pounds per acre. Boron in excess is toxic to plants, but apple and 

 other tree fruits are not as sensitive to boron as are many other cultivated plants. 



Blueberry Culture. (J. S. Bailey.) Mummy berry infection was reduced 

 about 50 percent in 1945 by spraying four times with Fermate.^ This work is 

 being continued in 1946. 



DDT and cryolite as dusts were applied to control the cranberry fruit worm. 

 Since the infestation was very light, no significant differences were observed. 

 However, it was determined that the fluorine on berries dusted June 13 with 

 cryolite was well below the Federal tolerance. 



Several new blueberry selections were added to the Experiment Station col- 

 lection during the year. 



The blueberry stunt, a virus disease, was found in Massachusetts in the sum- 

 mer of 1945. A careful survey was made of most of the larger plantings. In 

 most cases where the disease was found the grower promptly removed all in- 

 fected or suspicious bushes. This disease has probably been in Massachusetts 

 for a number of years, but it does not appear to be spreading. 



Nutrition of the High-Bush Blueberry, Especially in Relation to Soil Reac- 

 tion. (J. S. Baile}'.) After five years of manuring, there is still no evidence of 

 any toxic effect of applications of manure as heavy as 20 tons per acre. 



Several years' experience indicates that blueberries can be grown in a rather 

 heavy sod provided plenty of nitrogen is applied and the plants are not in a 

 situation where moisture becomes the limiting factor. 



Much more chlorosis than usual appeared in some of the blueberry plantings 

 in the early summer of 1946, following the application of ammonium nitrate in 

 place of the usual sulfate of ammonia. This chlorosis is most noticeable on the 

 varieties Sam and Pemberton. 



Control of the Peach Tree Borer. (J. S. Bailey.) Paradichlorobenzene, ethyl- 

 ene dichloride, and propylene dichloride were applied again in the fall of 1945 

 at the standard dosages. Too few borers were present to make comparisons of 

 effectiveness possible. Again there was no sign of injury resulting from any of 

 the treatments. A very satisfactory emulsion of propylene dichloride in water 

 was made by using oleic acid and triethanolamine. 



Magnesium Deficiency in Massachusetts Apple Orchards. (J. K. Shaw and 

 W. D. Weeks.) The typical leaf scorch characteristic of magnesium deficiency 

 was rather uncommon in our orchards in 1945. Yet chemical analysis of the 

 leaves showed a tendency for the magnesium content to be lower rather than 

 higher. Trees which had been treated with dolomitic limestone held up better 

 than others treated with Epsom salts. A possible explanation is that magnesium 



^The results of this experiment will appear in Volume 47 of the Proceedings of the American 

 Society for Horticultural Science. 



