Crown-Gall of Apple and Peach 



THE EXPERIMENT WITH APPLES 



1 



2 



3 



4 



5 



6 



7 



8 



9 



s 



We 



S 



We 



S 



We 



S 



We 



S 



We 



TO 



We 



TO 



We 



TO 



Wa 



TO 



Wa 



B 



Wa 



B 



Wa 



B 



A 



B 



Wa 



K 



Wa 



WR 



Wa 



WR 



Wa 



K 



WR 



K 



K 



Apple trees, of several varieties, bearing evident lesions of crown-gall 

 were procured in the autumn of 1910. On April 20, 1911, photographs 

 were made of the.trees^ and the trees were set in the garden. On May 6, 

 health}^ trees were procured, photographs were made, and the trees were 

 interspersed with the diseased trees as shown in the accompanying plan 

 (figure 1). All the trees were two years from the bud and were on im- 

 ported French stock. Practically all of them, except for the galls, would 



A 

 B 

 C 

 D 



Figure 1. plan of the apple crown-gall experiment 



Each character represents a tree and indicates the name of the variety according to the following key: 

 A, Alexander; B, Baldwin; K, Tonapkins King; 5, Northern Spy; TO, Twenty Ounce; Wa, Wagner; We, 

 Wealthy; WR, Wolf River. Bold-face letters represent galled trees; light-face letters represent healthy 

 trees 



have been graded as best-quality trees. The notable exception is tree 

 C-6, variety Alexander, which was small in diameter and bore a veiy large 

 gall at the crown. 



The trees were pruned very lightly from year to year, and in all cases 

 the pruning consisted in the entire removal of undesirable limbs. or branches. 

 No heading-back was done. 



. A record of the general appearance of the trees was made twice each year, 

 always without notes of the previous condition. For the most part the 

 records are normal and may be tabulated without comment. One tree, 

 C-3, Avas girdled by mice in the winter of 1913-14. A renewal developed 

 but was winterkilled the following winter. The tree was removed on 

 May 28, 1915, when it was found that the galls had enlarged appre- 

 ciabl.v (figure 2). The record of this tree previous to injury is shown 

 in table 1. 



The records for the apple trees are given in table 1. Before examining 

 the records or deriving any conclusion, the reader should have in mind 

 a number of items. (1) It is now evident that the experiment was not 

 planned on a large enough scale to give the best results, and particularly 

 there were not enough healthy trees planted for comparison. This was 

 not an oversight on the part of those planning the experiment, but rather 



— - II m 



* The photographs are on file in the Department of Plant Pathology at Cornell University under the 

 number 5727. None is reproduced here because the negatives are uniformly poor and suitable repro- 

 ductions cannot be made. Camera and plates were tested in order that uniformly good photographs 

 might be obtained without waiting to develop the negatives. When all negatives were found to be uni- 

 formly bad, it appeared probable that the shutter of the camera had been tampered with in the interim. 

 The original negatives show the location and size of the galls very readily, and they proved most useful 

 when the trees finally were removed. 



