Askew and associates (4, 5) in New Zealand sprayed Cox's orange apples 
about mid-December and mid-January with calcium acetate, potassium, and sodium 
and with superphosphate and borax in an attempt to control bitter pit. Orchards 
on two soil types were used. Sprays altered the chemical composition in both 
fruits and leaves in minerals and in amount of sugars and acids. In one season 
calcium sprays highly significantly reduced the amount of bitter pit in one 
orchard, but not in the next season. In the second orchard calcium sprays gave 
best results, but the treatment was not significantly beneficial. Potassium, 
sodium, and magnesium were detrimental and increased the incidence of bitter 
PLE 
Askew and associates (6, 7) reported that total ash content of the fruits 
was significantly positively related to increasing incidence of bitter pit. 
High values of the ratios Mg/Ca, K/Mg, K/Ca, and K/N accompanied high incidence 
of bitter pit in) the; Eruits. 
In studies on leaf analysis van Der Boon and associates (169) found that 
bitter pit increased as the K/Ca ratio in the leaves increased. ain 
Bouhier (24) showed that bitter pit in apples was strikingly associated 
with high values of the ratio of K + Mg/Ca in harvested fruits. The disorder 
was not found in Grimes Golden, Winesap, or Golden Delicious in which the ratio 
was below 22. In Belle de Boskoop and Reine des Reinettes bitter pit occurred 
in fruits with values of 28 to about 35, but not in those with 23 or lower. In 
Cortland with an average ratio of 53, bitter pit was very severe. 
Oberly and Kenworthy (120) reported that under Michigan conditions an 
increase of borofi in the leaves and mature fruit tissues may increase the inci- 
dence of bitter pit. The incidence of bitter pit increased as size of fruit, 
leaf boron and potassium, and fruit boron, potassium, phosphorous, and nitrogen 
increased. Conversely, the incidence of bitter pit decreased as leaf magnesium 
and manganese, and fruit calcium and manganese increased. 
Martin and associates (100) found that if calcium was withheld from trees 
of the Sturmer variety the fruits became highly susceptible to bitter pit. 
Fruit content of nitrogen, potassium, phosphorous, and magnesium was high and 
calcium was low. The molar decrease in calcium was much less than the molar 
increase in the other elements. They found no evidence of a disturbed balance 
between the elements in the fruit. Ratios of magnesium to calcium or of magne- 
sium and potassium to calcium emphasized the differences between fruits with low 
calcium and fruits with normal calcium. However, these ratios did not have any 
physiological significance, and they may detract from important predisposing 
factors such as the increase in nitrogen and rate of respiration (96). When 
magnesium was withheld, the incidence of bitter pit was not significantly dif- 
ferent from that of fruits that received a complete fertilizer. The results 
obtained from withholding magnesium further emphasize the specific importance 
of calcium in the fruit physiology. Pitted fruits on trees that were adequately 
supplied with calcium appeared to be the result of localized deficiencies of 
calcium. 
Kidson (81) found about four times as much calcium in the skin of apples 
as in the underlying flesh. Healthy and pitted fruits from a number of orchards 
showed a consistent relation between pitting and low calcium levels in the skin 
and flesh. 
Yamazaki and Mori (183) reported that fruits from trees grown in solution 
culture for 2 years without calcium were severely affected by bitter pit. A 
lack of magnesium did not produce pit. Under similar culture Yamazaki and 
others (184) reported that the incidence of bitter pit at harvest was severe 
on Jonathan apples supplied with high nitrogen. Bitter pit increased signifi- 
cantly as the calcium supply decreased. 
169 
