14 



RECOMMENDATIONS FOR USE OF CALCIUM SPRAYS 



William J. Bramlage and Mack Drake 

 Department of Plant and Soil Sciences 



Our surveys of Massachusetts orchards have shown that concentrations of 

 calcium (Ca) in apple fruits are more variable than those of any other 

 mineral, and that fruit from many orchards are Ca def icient--which makes 

 them more susceptible to breakdown, bitter pit, scald, and rot during and 

 after storage. To combat this problem, most Massachusetts apple growers 

 have been foliar spraying calcium chloride (CaCl?) periodically during the 

 growing season. Our current recommendations for use of Ca sprays in apple 

 orchards are described here. 



Many Ca-containing compounds have been tested for use on apples and a 

 number of different ones are commercially available. Technical grade 

 (77-80%) CaCl2 is the material we recommend. We have tested a number of 

 different materials and found that the amount of Ca that they put into 

 apples is directly proportional to the concentrations of soluble Ca in the 

 spray solution. With the exception of the relatively insoluble material, 

 Ca{H2P04)2, which was ineffective in increasing fruit Ca, neither the for- 

 mulations of the material nor the chemical that is associated with Ca in the 

 material has significantly affected the final result. Technical grade CaCl2 

 is the most economical material for adding the needed Ca to apples. 



Foliar CaCl2 sprays should begin about 3 weeks after petal-fall and be 

 repeated at 2-week intervals, totaling about 8 applications for the season. 

 The CaCl2 can be combined with pesticide sprays. Since young leaves tend to 

 be sensitive to CaCl2, we recommend using 6 lbs per acre in each spray until 

 mid-July, and then 8-10 lbs per acre until harvest. The goal should be to 

 apply a total of 70 to 75 lbs of CaCl2 per acre for the season. While we 

 recommend the above rates, we have fouhd that minor alterations of these 

 rates and timings have been just as effective in raising fruit Ca levels as 

 the recommendations so long as the same total amount of CaCl2 is applied. 

 In other words, if lower rates are used'j more sprays are needed. When 

 higher rates are used the risk of damage from Ca sprays is increased. 



Ca sprays can cause damage to leaves or even fruit. With CaCl2, leaves 

 are much more likely to be damaged than fruit, the injury normally appearing 

 as browning of the leaf margins. We have sought a less phytotoxic form of 

 Ca but have found no material that was safer than CaCl2 when applied at an 

 equal soluble-Ca concentration. Tests in other areas have shown that 

 calcium nitrate (Ca(N03)2) is less damaging to leaves than CaCl2, but is 

 more likely to cause fruit injury (black spots on the lenticels). We recom- 

 mend the use of CaCl2 rather than Ca(N03)2 to minimize the risk of fruit 

 damage. While leaf injury is undesirable, we have observed no detrimental 

 effect to either fruit or trees when mild symptoms have developed. However, 

 severe damage could cause earlier fruit ripening and dropping. 



