A Re-examination of the Boron 

 Recommendations for Apple Trees 

 in Massachusetts 



William J. Bramlage and Sarah A. Weis 



Department of Plant & Soil Sciences, University of Massachusetts 



Boron (B) is an essential element for plant 

 growth, and in Northeastern North America apple 

 growers must contend routinely with its deficiency. 

 B deficiency can reduce tree growth, cause corking 

 in fruit, and cause premature fruit drop. B defi- 

 ciency also interferes with movement of calcium (Ca) 

 in plants, and can therefore cause or antagonize a Ca 

 deficiency problem in apples. 



Our primary recommendation for B treatments 

 in apple orchards has been to apply B to the soil every 

 third year [Fruit Notes 49(2):8-13]. The actual 



amount of B to be applied varies with tree size. An 

 alternative approach is annual foliar applications of 

 Solubor™ in the first two cover sprays. 



In New York, recommendations for B applica- 

 tions in apple orchards are different from ours [Fruit 

 Notes 47(2):20-26]. There, annual treatments, 

 whether through soil or foliar application, are rec- 

 ommended, and higher application rates are sug- 

 gested for certain conditions. 



To re-examine the adequacy of our B recommen- 

 dations, we carried out a 4-year experiment at the 

 Horticultural Research Center in 

 Belchertown. In 1987, the experi- 

 ment was established in a block of 

 Marshall Mcintosh trees on M.7A 

 rootstock, planted in 1981. 



A complex set of treatments was 

 designed to test our current recom- 

 mendations against various modifica- 

 tions of these recommendations 

 (Table 1). Thus, one treatment con- 

 sisted of 1 lb of borate per tree applied 

 to the soil every third year. (Since all 

 trees in this block received this treat- 

 ment in 1986, it would be applied in 

 1989.) A second treatment consisted 

 of annual sprays of 1/2 lb of Solubor 

 per 100 gallons of water at the first 

 and second cover sprays. (These two 

 treatments are the options that we 

 recommend.) 



The modified treatments were: 1 

 1/3 lbs of borate per tree every second 

 year, 1 lb of borate per tree every year, 

 1 1/3 lbs of borate every year, and 1 2/ 

 3 lbs of borate every year. Also, one 

 treatment consisted of Solubor 

 sprayed at 1 lb per 100 gallons of 

 water at the first two cover sprays 

 (twice our recommended rate). 



We hoped to evaluate our recom- 

 mendations by comparing the bene- 



10 



Fruit Notes, Spring, 1991 



