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Some growers have chosen to use Ca(N03)2 to reduce the risk of leaf 

 injury. We have applied Ca(N03)2 in concentrations of soluble Ca equal to 

 those of the recommended rates of CaCl2, and have found that equal amounts 

 of Ca are added to the fruit. However, the overall effects of the treat- 

 ments on fruit and trees have not yet been determined, and we believe that 

 CaCl2 is the material of choice. 



To minimize risk of foliar damage from CaCl^ sprays, care must be 

 taken. Sprayers need to be calibrated. CaCl2 should always be mixed in a 

 pail of water and be added last, when the spray tank is nearly full, to 

 ensure thorough mixing in the tank. The spray tank must have sufficient 

 agitation to maintain thorough mixing during spraying. Risk of damage is 

 greatest on weak trees or injured foliage. We are aware of no known incom- 

 patibility of CaCl2 with commonly used pesticides, but since formulations 

 and combinations frequently change, users should be alert to any unusual 

 behavior of materials in the spray mixtures. Do^ not mix CaCl2 with Solubor 

 or Epsom salt sprays . Do not apply CaCl2 in excessively hot weather. 



Foliar CaCl2 sprays may be applied as either dilute (300 gal per acre) 

 or lOX concentration (30 gal per acre). We have seen indications that 

 uptake of Ca by apples can be greater from concentrated than dilute sprays, 

 but other researchers have found that these methods of CaCl2 application add 

 equal amounts of Ca to apples. Some growers have applied CaCl2 at higher 

 than lOX without problems, but we have no data on their effectiveness. If 

 CaCl2 is applied in a dilute form and separate from pesticides, a non-ionic 

 wetting agent should be added, but since most pesticides include wetting 

 agents in their formulation the addition should not be needed when CaCl2 and 

 pesticides are combined. 



The initial pH of commercial CaCl2 in water is about 10.3, since small 

 amounts of free calcium oxide form calcium hydroxide in water. There is 

 evidence that this high pH may reduce effectiveness of some pesticides. We 

 therefore, have recommended adding 2 quarts of 5% vinegar per 100 pounds of 

 CaCl2 to neutralize the alkalinity and bring the spray solution to about pH 

 6.0. The addition of vinegar will not affect uptake of Ca by the apples, or 

 injury to the foliage. (Please see the following articles for more infor- 

 mation about this pH problem.) 



Use of CaCl2 as a foliar spray for apple trees is an established annual 

 practive in mo' t Massachusetts apple orchards. While this material can be 

 phytotoxic, thf risk of injury is minimized by attention to details when it 

 is used. The !)enefits from its use are substantial. When 70 to 75 lbs per 

 acre are applied, potential storage life of the fruit can be greatly 

 improved. However, many growers apply less than 70 lbs per acre, and poten- 

 tial benefit declines proportionally as less than this total is applied 

 during the growing season. Our recommendations are designed to obtain the 

 greatest benefit from CaCl2 most efficiently, while minimizing the risk of 

 foliar damage. Since there is no carryover of this Ca benefit, it is 

 necessary to apply the sprays at full dosage each year for maximum benefit. 



