CORK SPOT OF DELICIOUS AND SUGGESTIONS FOR ITS POSSIBLE REDUCTION 



W.J. Lord, 

 Department 



Mack Drake and J.H. Baker 

 of Plant and Soil Sciences 



Bitter pit has long been a problem in Massachusetts, particu- 

 larly on Baldwin and Northern Spy. Of the varieties now commer- 

 cially important, Cortland appears to be the only one on which 

 bitter pit is of major concern. However, cork spot is a disorder 

 similar to bitter pit. It was evident this past season that cork 

 spot can be a serious problem on Red Delicious, Because a large 

 number of young Delicious trees are now coming into production and 

 because of the high market value of their fruit, this disorder 

 could take on major economic significance. 



Chemical analysis of peel of Red Delicious fruit by Drs. Mack 

 Drake and John Baker, Department of Plant and Soil Sciences, Uni- 

 versity of Massachusetts, this past season, showed that low calcium 

 in the peel was associated with both cork spot and bitter pit. 



Those of you that were in attendance at the New England Fruit 

 meetings held on January 5 and 6, 1972, heard Drs. Drake and Miklos 

 Faust, U.S.D.A., discuss the problems associated with increasing 

 calcium in the fruit. (These presentations will appear in the Pro- 

 ceedings of the New England Fruit Meetings.) It was evident from 

 these talks that (1) the many factors that increase bitter pit also 

 influence cork spot; and (2) that effective control measures of 

 both disorders are yet to be perfected. The following measures for 

 the reduction of cork on Red Delicious were suggested. 



1. Continue to apply 3 tons of limestone per acre e\/ery 2 to 

 3 years. Where high magnesium lime was used in the last 

 application, the use of a more soluble high calcium lime 

 will act more rapidly and will provide more calcium. 



2. Change from ammonium nitrate or urea sources of fertili- 

 zer nitrogen to calcium nitrate. Calcium nitrate ferti- 

 lizer quickly increases the level of soluble soil calci- 

 um, increases the downward movement of calcium, and 

 raises the pH of the soil. 



