Bitter Pit in AppUfi. 407 



apples from Iowa, Missouri, Virginia, New York, Oreg-on and 

 Washington. The cause is uncertain, but it is suspected to be 

 due to injury by arsenate of lead used in spraying. Low tem- 

 peratures retard or prevent its development. 



P. O'Gara ('^ Better Fruit," 1911, p. 28) writes " On the spot- 

 ting of apples by arsenate of lead." The spots are confined to 

 the epidermal and sub-epidermal cells. An unsprayed orchard 

 with neglected trees did not develop a single spotted fruit 

 except where the trees were sprayed with a soluble arsenical 

 poison. The greatest amount of injury was found in trees in the 

 very best condition, growing prize fruit and regularly treated. 

 Analyses of 10 gramme samples of the epidermal and sub-epider- 

 mal tissues showed that the black and red spots contained from 

 0.03 to 0.05 milligramme, while the apparently sound skins 

 showed 0.0'25 milligramme of arsenic. One analysis of very badly 

 spotted apples showed a quantity of arsenic equal to 0.3 mg. of 

 As^O-^O.OOo grain). Tliere is no danger from eating such 

 apples, as at least 5 milligrammes are required to produce a 

 marked effect. The author advises the use of at least one 

 pound of unslaked lime with each pound of lead arsenate. 



In view of the foregoing results direct tests were made with 

 various spraying materials. 



Ar.se imfe of Lead. — That this and other spraying materials 

 termed " insoluble " are not absolutely so was shown by the 

 fact that a clear saturated solution from Sherwin-Williams' new 

 process arsenate of lead contained 0.06 of dissolved solids, 



Jonathan apples rubbed with the solid, then wiped clean and 

 wetted daily with water, developed numerous black spots at 

 the lenticels, but even after eight weeks none exceeded 1 to 2 

 mm. diameter and 0.5 mm. depth, and the pits were no larger 

 even when minute punctures not exceeding 0.2 mm. diameter 

 were made in the skin prior to rubbing with arsenate of lead. 

 If fragments of the cuticle 1 mm. square were removed, dark, 

 circular brown pits formed, increasing to 2 to 4 mm. diameter 

 and 1 to 3 mm. deep in eight weeks. Prepared apples placed for 

 one week in a clear filtered solution from 5 grams of arsenate 

 of lead in 1 litre of water, filtered after standing, showed in 

 three weeks well-developed pits 1-2 mm. deep beneath each pre- 

 pared spot. With a similar solution from Paris Green the pits 



