Effects of Calcium Salts on Flyspeck and 

 Sooty Blotch of Golden Delicious Apples 



Daniel R. Cooley and Arthur Tuttle 

 Department of Plant Pathology 



Wesley R. Autio and Sarah Weis 

 Department of Plant & Soil Sciences 



Apple producers in the northeastern United 

 States frequently apply calcium chloride (CaClj) to 

 apples as summer sprays in order to improve fruit 

 storability. These sprays need to be applied several 

 times from July to harvest for optimal effects, and 

 may be combined with fungicides to control 

 summer diseases, particularly flyspeck and sooty 

 blotch. The incidences of these diseases vary from 

 year to year, and they may require minimal 

 controls one season, but significant efforts in 

 another. 



The effects of calcium chloride on flyspeck and 

 sooty blotch have not been examined. Other cation 

 salts, notably sodium bicarbonate, have been 

 effective in controlling powdery mildew on some 

 plants; therefore, it would be worthwhile to 

 evaluate the extent of the effects of calcium chloride 

 and related cation salts on sooty blotch and 

 flyspeck. 



This experiment was designed to evaluate the 

 effects of calcium chloride, calcium nitrate 

 (CaNO^), and potassium carbonate (KCO3) on the 

 incidence of flyspeck and sooty blotch on apple fruit. 

 The cation salts in combination with a commercial 

 wetting adjuvant (Latron B1956) were applied at 2- 



week intervals starting in mid-July, and were 

 compared to a standard fungicide treatment 

 (Benlate plus captan) applied at a 3-week intervals 

 and to non-treated controls. All sprays were 

 applied at 6X with an air blast sprayer. Trees were 

 mature Golden Delicious/M.7, located in four rows 

 at the University of Massachusetts Horticultural 

 Research Center, Belchertown. Each treatment 

 was applied to 3-tree plots, and was replicated 5 

 times. The treatments with rates are listed in Table 

 1. 



On 16 October, seventy fruit from the center 

 tree of each plot were harvested randomly, and the 

 presence or absence of flyspeck or sooty blotch was 

 recorded. Ten apples were selected at random from 

 each sample and weighed. The flesh firmness of 

 these 10 apples was measured (2 readings per 

 apple). Four plugs were taken from each apple and 

 frozen for later calcium determination. The 

 remaining apples were kept at 32°F. For calcium 

 determination, plugs were dried and ashed, and 

 then samples were analyzed using atomic 

 absorption spectrophotometry. 



On 26 February 1996, samples were removed 

 from cold storage, and the firmness of 10 apples per 



Table 1. List of treatments applied to Golden Delicious apples from mid- July to harvest, 1995. 



Treatment 



Amount/100 gal 



Timing interval (wks) 



Captan 50WP + Benlate 50WP 



CaCl2+ Latron B 1956-1- vinegar 



CaN03-h Latron B1956 



CaClj + CaNOj + Latron B 1956-1- vinegar 



KCO3 -I- Latron B1956 



Latron B1956 



Control (no spray) 



1 lb. + 6 oz. 



3.3 lb +3 fl.oz+2.2 fl.oz 



5.3 1bH-3fl.oz 



2.5 lb -H4.0 lb+3 fl.oz-i-2.2 fl.oz 



3.0 lb + 3 fl.oz 



3 fl. oz. 



none 



3 

 2 

 2 

 2 

 2 

 2 



Fruit Notes, Spring, 1996 



17 



