Apr. 38, X933 
Peach Rosette^ an Infectious Mosaic 
309 
it appears in the peach, the shortened internodal growth, and the mot¬ 
tling of the leaves indicate that the causal entity had been transferred 
from the peach to the apricot. 
On September 2, 1920, two buds were taken from the rosetted Royal 
apricot and inserted in a peach seedling, growing in a pot in the green¬ 
house. These buds remained dormant until April, 1921, when they 
began to develop mottled leaves. The new growth of the peach seedling 
developed typical rosettes (PI. i, B). Both the potted rosetted peach 
seedling and the rosetted Royal apricot tree died during the summer of 
1921. 
Experiment 3 shows that the causal entity of rosette may be trans¬ 
ferred from peach to apricot, and from apricot to peach, proving that 
apricot and peach rosette ara identical as far as causal entity is concerned, 
but somewhat different in external manifestations of the disease. 
STUNTING OF APRICOT GROWTH BY ROSFTTK 
Experiment 4.—^In the spring of 1920 another case of natural infec¬ 
tion of peach rosette (PI. 3, A) developed in a 6-year-old seedling peach 
tree growing in the same orchard about 150 feet from the rosetted seed¬ 
ling described in experiment i. 
On June 19, 1920, buds from this second rosetted seedling peach were 
inserted into a branch of a one-year-old Moorpark apricot about a foot 
above the ground. By August 20, 1920, both of the peach buds had 
grown into rosetted shoots (PI. 5, B), but the stock showed symptoms of 
rosette only in the growth immediately below the inserted peach buds, 
where the apricot leaves became mottled. An apricot limb adjoining 
the one which was inoculated, made a growth of 4 feet and 4 
inches during the summer of 1920, and bore normal green leaves. There 
was no growth of lateral buds. On April ii, 1921, the lateral as well as 
the terminal buds on all the apricot brandies had produced mottled, 
greenish yellow leaves, in marked contrast to the normal green leaves of 
the near-by healthy apricot. This indicated that the causal entity of 
rosette had spread throughout the apricot tree. During the summer of 
1921 this Moorpark apricot tree grew very slowly, the maximum growth 
of any one branch being 5 inches. During the same tirne the near-by 
healthy apricot tree made a growth of 4 feet and 9 inches. Plate 3, B 
(taken in the fall of 1921) shows the .inoculated apricot tree writh a back¬ 
ground, at the left, in contrast to the healthy apricot tree at the right. 
An indication of the stunting effect of rosette is shown by the inoculated 
tree in which the maximum vertical growth of 4 feet and 4 inches made 
during the summer of 1920 represents pormal growth; while the maxi¬ 
mum horizontal growth, 5 inches, represents development made during 
the summer of 1921 under the retarding influence of rosette. 
PEACH TO cultivated PLUM 
Experiment 5. —On August 6, 1919, a bud from a healthy Blue Dam¬ 
son plum was placed in the trunk of a healthy peach seedling which came 
up in the spring of 1919. This plum bud made a few inches of growth 
during the summer of 1919, and in the summer; of 1920, made a growth 
of more than 2 feet. Neither the plum branch nor the peach stock 
showed any symptoms of disease up to June 19, 1920, when two buds 
from the rosetted peach tree described in experiment 4, were inserted in 
