For control of bitter pit on green varieties, Baxter recommended: 
Calcium nitrate 8 pounds per 100 gallons of water with a wetting agent. Spray 
once or twice within 6 weeks of petal fall and again within a month of harvest. 
For red varieties the early season sprays could be calcium nitrate, but later 
sprays should be of calcium chloride 5 pounds per 100 gallons. He (14) found 
that covering the fruits during spraying did not reduce the effectiveness, but 
painting calcium salts on the fruits was more effective than foliar sprays. 
Wilkinson (178) published a brief review of the bitter pit problem with 
special reference to control of the disorder in England. Bitter pit is a prob- 
lem there only about 1 year in 5, and calcium sprays are not recommended as a 
general practice. Instead, fruit growers rely on approved orchard practices, 
proper picking maturity, and prompt cooling of the fruits. 
Results with calcium sprays for reducing bitter pit on apples from mature 
apple trees have in general been favorable throughout the world. Stevenson 
(158), however, in Australia reported that preharvest sprays of calcium chloride 
and calcium nitrate failed to reduce the incidence of bitter pit significantly 
on apples from young trees. All sprays caused some injury to the trees. The 
effect of fruit maturity on the incidence of bitter pit was significant. Cal- 
cium sprays are not recommended for the control of bitter pit in fruit from 
young trees. 
Recent investigations on bitter pit have also covered certain areas 
other than calcium nutrition. One that is of considerable interest in a report 
pertaining fe the possibility of bitter pit being caused by a virus. In 1933, 
Atanasoff & published a paper on bitter pit and raised the question of whether 
the disorder was caused by a virus. While the virus theory has not been ac- 
cepted, published research on the subject had been lacking. In 1962, Campbell 
and Luckwill (38) published the results of their transmission experiments with 
bitter pit conducted in England. They concluded from grafting tests that bitter 
pit is very unlikely to be a virus disease. 
Research has also continued on certain factors in the orchard and their 
relation to bitter pit. 
BUnemann (33) found that pitted tissues had less calcium and more mag- 
nesium than normal tissues. 
BUunemann (35) also found that tissues of Northern Spy apples affected 
with bitter pit had twice as much nitrogen as apple tissues that were free of 
bitter pit. Hill (70) found a highly significant positive relation between 
foliage nitrogen and the incidence of bitter pit. Nyhlen (117) reported that 
late applications of nitrogen increased the amount of bitter pit. 
Luchetti and Ferrigato (86) attributed the absence of bitter pit, in the 
Ferrara (Italy) region, in 1961 to the very dry summer and autumn. On the 
other hand, Nyhlen and Rootsi (119) found more bitter pit, during dry years, in 
apples from nonirrigated trees than from irrigated ones, The lowest incidence 
of pit occurred in plots with balanced nitrogen and phosphorous with or without 
potassium. Straw mulch appeared to favor pit in comparison with clean cultiva- 
tion. Incidence of pit did not appear to be related to size of fruit or extent 
of crop per tree. The last two statements are in disagreement with the findings 
of other researchers. 
Butijn and Van't Levin (37) reported less bitter pit in irrigated than 
in nonirrigated fruits of Cox's Orange Pippin. 
8/ Atanasoff, D, Bitter Pit of Apples: a Virus Disease? Yearbook of 
Agriculture 12:31-67. Sofia, Bulgaria, 1933. 
LFA. 
