We set up solutions containing different concentrations of iron, with and 

 without CaCl2. Iron caused severe spotting, and when it was combined with 

 CaCl2 the spotting was increased. We also prepared CaCl2 solutions, 12 lbs per 

 100 gallons, in a plastic bucket and in a rusty metal bucket. The CaCl2 

 solution in a plastic bucket caused no fruit spotting, but the one in the metal 

 bucket caused substantial spotting. Our purpose in this test was simply to 

 find out if this avenue might lead anywhere, and it is obvious that it merits 

 further study. It is also noteworthy that in the washing experiment, described 

 above, we had no spotting from 12 lbs of CaCl2 per 100 gallons in 1986-87, 

 whereas in previous years spotting occurred. The dipping tank used in these 

 tests is made of galvanized iron and after years of use was starting to rust. 

 Last summer it was painted, and so the CaCl2 solution in 1986 was no longer in 

 direct contact with iron. Further tests must be made to establish the 

 importance of iron in this problem but the implications are consistent with the 

 comments of our Australian colleague, who said that eliminating metal tanks 

 solved their spotting problem. 



In conclusion, it must be reaffirmed that a postharvest treatment with 

 CaCl2 can significantly increase storage potential of apples. It appears that 

 12 lbs of CaCl2 per 100 gallons of water is a reasonable compromise, increasing 

 fruit Ca levels significantly with a relatively small risk of spotting. (Note 

 that our assessment of spotting is very intense. Most of our "spotted" fruit 

 would still be in grade.) The CaCl^ must be Briner's Grade or purer , since it 

 is considered by authorities to be a food additive. The solution must contain 

 an appropriate fungicide, or mixture of fungicides, or severe rotting can 

 result. DPA or ethoxyquin can be applied with the CaCl2. We suggest adding 1 

 pint of vinegar per 100 gallons of solution to protect against possible adverse 

 effects of a high pH due to the CaCl2 ( Fruit Notes 50(2) : 18-20) . 



We suspect that spotting results from the solution that enters the fruit 

 openings during the dip. Our studies show that spotting is increased when DPA 

 or a surfactant is included in the mixture, when the fruit are significantly 

 warmer than the solution, or when substantial levels of iron are present in the 

 solution. Under these conditions, perhaps the CaCl2 should be reduced to 8 or 

 10 lbs per 100 gallons. 



We shall continue with these studies, to try to find conditions under 

 which the risk of fruit spotting from postharvest CaCl2 treatments can be 

 minimized or eliminated. These treatments have great value in increasing 

 storage life potential, and are extremely useful as a final technique when you 

 recognize at harvest time that a Ca problem exists. They are used routinely by 

 some Massachusetts growers, and are used extensively for apples in many parts 

 of the world. Their use should not be ruled out because of a fear of fruit 

 damage. However, they must be used with care, just as with any other chemical 

 application. 



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