4 6 
Journal of Agricultural Research 
VoL XXVI, No 2 
some 2 or 3 inches in longitudinal and transverse dimensions, and do 
not extend beyond the normal diameter of the limb by more than yi 
to i inch. The surface of such young galls is usually rough, fissured 
longitudinally, and but little cracked transversely. Several such young 
galls, on a seriously affected limb, may be seen in Plate i, A. Plate i, B, 
shows an old gall. Note that it is very prominent and deeply fissured. 
This is a feature which is characteristic of the older galls, and 
more especially of those encircling the limbs on which they are borne. 
Another feature which may be observed on encircled limbs is the con¬ 
striction forming just above and below the galls. This may be noted 
on Plate i, B, but more particularly on Plate 3, which shows the encircled 
limb shown in Plate 1, B, in a longitudinal section. The galls form 
principally on the limbs and the trunk, and occasionally, although 
rarely, on the crown and roots of the trees. Plate 2, A, shows the only 
gall found on the root system of a tree whose limbs had reached the 
far advanced stage of disease shown in Plate 2, B. On going through 
an affected spot in the orchard, galls of all sizes may be noticed, ranging 
from small eruptions 1 inch in diameter to highly prominent galls measur¬ 
ing 18 inches transversely, according to the age of the swellings. 
Alarming as this disease may seem to the casual observer, the presence 
of these tumors does not seem to have a very detrimental effect upon 
the vitality or productivity of the trees. Trees with as many as 10 to 15 
galls on them do not show any appreciable reduction in their seasonal 
growth or yield. Not until the galls have increased in number so as 
to become almost contiguous on the trunk or main limb (PI. 2, B), 
does the tree begin to show any signs of reduced vitality. Such a condi¬ 
tion rarely if ever obtains until after 10 or 12 years from the appearance 
of the first gall. Up to the present time no trees are known to have 
died of this disease; nevertheless it seems beyond doubt that the affected 
trees will, if left to themselves, die ultimately of the disease, or at least 
suffer such a reduction of vitality as to make them worthless. 
Investigation has established the following facts: (1) The disease 
never occurs on young trees. All the affected trees are advanced in 
years, usually not much less than 25 to 30 years old. (2) Galls form 
only on fairly old wood of these trees. In no case have any galls been 
found on wood less than 7 to 10 years old, as estimated by the yearly 
pruning cuts. (3) The disease, on the apricot, is practically restricted 
to the Moorpark variety. 
In Mr. T. C. Gorrie’s orchard at Hayward, Calif., where most of the 
field work has been carried out, rows of Moorpark apricot trees are 
planted beside Blenheim apricots of the same age, with occasionally 
trees of the two varieties mixed in the rows. Of about 80 Moorpark 
trees, nearly 60 are affected with the disease, while only a single gall 
has been found among all the Blenheim trees in this 8-acre orchard. 
Although trees of other apricot varieties may become affected, no 
cases have come to the writer’s knowledge. 
GROSS ANATOMICAL FEATURES OF THE GALLS 
The anatomy of the disease has been found very characteristic, and 
its main features have proved to be of great diagnostic value. Plate 3 
shows a longitudinal section through a limb bearing a gall. An examina¬ 
tion of the tumor, with regard to the tissues involved in its formation, 
brings out the following facts: 
