-17a- 

 ADDENDUM 



After this issue of FRUIT NOTES had gone to press, it came to 

 our attention that the recommendations for use of CaCl2 appear to 

 be in conflict with statements in the "Annual March Message to Massa- 

 chusetts Fruit Growers (1983)", issued by Ronald Prokopy, William 

 Coli and Thomas Green of the Department of Entomology. To avoid 

 confusion from "mixed messages", the following additional comments 

 are presented: 



Beginning about 1975, in Massachusetts we recommended separating 

 the applications of CaCl2 and pesticides. However, for the past 5 

 years many Massachusetts growers have combined CaCl^ with pesticide 

 sprays without observed reduction in effectiveness of pesticides. 

 Nevertheless, as we warn on page 17, addition of CaCl2 can signifi- 

 cantly raise the pH of the spray solution, which theoretically can 

 reduce the effectiveness of the pesticides. 



This past year. Dr. George Greene conducted experiments at Big- 

 lerville, PA which showed that while CaCl^ raised the pH of water 

 it caused no measurable increase in disease or insect damage to apples 

 when combined with the pesticides he was using. It should be noted, 

 however, that some other researchers have reported evidence of reduced 

 effectiveness of pesticides at these high pH ' s . 



In 1982 a number of Massachusetts growers added vinegar to lower 

 the solution to about pH 6, as recommended on page 17, to their mix- 

 ture of CaCl2 and pesticides. There was no dissatisfaction with 

 results . 



Nevertheless, since some researchers and some states have issued 

 warnings of possible ineffectiveness of vinegar as a remedy, the 

 following additional steps can be taken if a grower feels that they 

 are necessary . 



1. Use CaCl^ of a higher purity grade. Technical grade (77- 

 80l)CaCl2 will affect pH somewhat more than high purity 

 grade materials. However, the higher purity grade is 

 much more expensive and less available. 



2. Apply CaCl2 sprays separately from pesticides. 



3. Use a commercial buffer rather than vinegar to lower the 

 pH. Some concerns have been published that acetic acid, 

 the chief component of vinegar, may not be stable over 

 long periods in the spray mixture. However, it should 

 also be noted that some commercial buffers may cause Ca 

 to precipitate from solution, thereby reducing the value 

 of the CaCl2 sprays. 



It should be recognized that we are not recommending the above 

 steps. We are alerting growers to concerns that have been raised 

 elsewhere, and to steps that can be taken if they feel that these 

 concerns warrant extra precautions. 



William J. Bramlage, William Coli and Mack Drake 



