no Journal of Agricultural Research voi. xii. no. 3 



Ewart (6, 7) concluded that the disease was the result of local poison- 

 ing and mentioned spray materials and the toxic salts of the soil as 

 possible causes. 



White {21) considered that the disease was the result of the poisoning 

 effects of arsenical compounds and other spray materials. 



McAlpine (9-12) thought that the disease was produced by a shortage 

 of water in the affected tissue and that the condition might be brought 

 about either by transpiration exceeding the water supply or by the growth 

 of the pulp tissue being too rapid to allow time for the formation of the 

 new vascular tips needed to supply it with water. He found that there 

 was slightly less of the disease on trees receiving two irrigations than on 

 those receiving one. 



DESCRIPTION OF BiTTER-PiT 



Bitter-pit makes its first appearance as water-soaked bruiselike 

 spots on the surface of the apple. The epidermal tissue is at first entirely 

 normal, the spotted effect being due to the breaking down of cells in the 

 subepidermal region. The spots soon become depressed into rather 

 definite pits, 2 to 6 mm. in diameter, hemispherical in shape, and fairly 

 regular in outline. They develop a higher color than the surrounding 

 surface of the apple, becoming a deeper red than the adjacent tissue 

 when occurring on the colored portion of the fruit and a darker green 

 when on the lighter parts (PI. 2, A). As the disease advances farther, 

 the spots take on a brownish color owing to the dead pulp cells beneath 

 the epidermal layers, and in late stages of the trouble the affected area 

 may entirely lose its normal color, becoming a deep brown (PI. 3, A). 

 The diseased tissue is dry and spongy, the cells are collapsed but still 

 full of starch, and the cell walls show no sign of thickening or disinte- 

 gration. The affected tissue often has rather a bitter taste, and this 

 together with the sunken nature of the spots has given rise to the term 

 '' bitter-pit." 



The pits are usually associated with the terminal branches of the 

 vascular bundles, and the surface spotting is often accompanied by a 

 browning of the vascular tissue deeper in the fruit, giving the appear- 

 ance of numerous brown spots in the flesh when the apple is cut (PI. 2, B). 

 This internal browning is especially common in the tissue within a centi- 

 meter of the surface of the apple. While the internal browning and sur- 

 face pitting are commonly associated, either may occur without the other. 



Bitter-pit is often confined to the calyx half of the apple. Baldwin, 

 Northern Spy, Grimes, Jonathan, and Yellow Bellflower are especially 

 susceptible to the disease; and Rome Beauty and Winesap are fairly 

 resistant; but almost all varieties are sometimes affected. 



Bitter-pit is very similar in appearante to rosy-aphis stigmonose, but 

 the latter disease is not accompanied by a browning of the vasculars 

 and the subepidermal tissue has a firmer texture and a darker color than 

 is the case with bitter-pit. Stigmonose is found only on limbs that 



