14 BULLETIN 684, U. S. DEPARTMENT OF AGEICULTUEE. 



Missouri. — Margins of cankers are intact except in tlie cases of very j'onn.^ 

 branches (water sprouts). 



Jonathan. — Canliers are very large on older branches, with small amount or 

 cracking at margin. 



Grimes. — Cankers have margins cracked ; probably will survive. 



Winesap. — Margins of cankers are somewhat cracked and much roughened ; 

 probably will not survive. 



Yellow Newtown. — Margins of cankered areas are separated from bark of 

 living portion of branch, and callus is forming. 



On June 26, 1917, the following notes were taken: 



Ben Z)ff-ms.— Cankered areas irregularly cracked at margins in case of 

 younger limbs. Layers of callus are forming. Those on older wood have mar- 

 gins intact. Acervuli are abundant. 



York Imperial. — Slits have healed over. They are similar to the conti'ol slits. 



Missouri. — Margins are irregularly cracked at the sides but not at the ends 

 of the cankers. The cracks are not quite so large as in case of the Jonathan 

 variety. 



Jonathan. — Margins are cracked at the sides and separated from the living 

 bark, from which callus is forming. There is no such separation, however, at 

 the ends of the cankered areas. 



Grimes. — Margins are cracked and a callus layer is forming. Acervuli are 

 abundant. 



Winesap. — The same as Grimes. 



Yellow Wewtown. — Lips of callus nearly meet. The dead bark is nearly all 

 shed. The remnants of the old dead bark, however, produced acervuli and 

 spores after 48 hours in moist chamber. The acervuli were very small and the 

 spores few. 



By September 19, 1917, the slits on the York Imperial and Yellow 

 Newtown were healed over and the dead cankered bark completely 

 eliminated. The cankers on the Ben Davis were persisting without 

 any apparent change. In the case of the Missouri and the Jonathan 

 varieties there was little or no nevf growth. Layers of callus were 

 forming, but the old cankers with their dead bark still persisted. 

 The former large lesions on the Grimes were nearly healed over, 

 with elimination of most of the old dead bark. The lips of the layers 

 of callus were nearly meeting. The Winesap cankers were similar 

 to those of the Grimes except that the healing process had not been 

 quite so rapid and hence more dead bark remained. In the case of 

 all varieties except the York Imperial and Yellow Newtown, the fruit 

 below the cankered limbs was infected with bitter-rot. The infected 

 areas extended to the lowest limbs and were about 6 feet across. The 

 infection was not carried to the fruit of adjacent trees, only the 

 fruit of trees in which cankers had been artificially produced being 

 affected. This shows how restricted is the dissemination of the dis- 

 ease and why it may become localized in certain trees. 



As a result of these experiments it appears that the Ben Davis, 

 Missouri, and Jonathan varieties are quite susceptible to the canker 

 disease. The Grimes is apparently not quite so susceptible, but is 



