5^2 
Journal of Agricultural Research 
Vol. XIV, No. 13 
PERCENTAGE OF LEAF PETIOLES SHOWING GALLS 
Leaves were gathered from a tree of Populus deltoides on July 26, 1916, 
to ascertain the percentage of leaf petioles having galls upon them, and 
to learn whether galls occurred in greatest numbers in any one portion 
of the tree as regards the height above the ground. Galls are found upon 
comparatively small trees and upon the largest specimens. 1 * * * The tree 
selected was about 30 feet in height and the infestation appeared to be 
an average one for the particular locality. Branches were broken from 
it at random at various heights. The leaves were then stripped from 
the branches and counts made of those leaves showing galls and those 
not infested. It was found that there was a considerable variation in 
the percentage of leaves showing galls on different branches, but the dis¬ 
tance above the ground apparently had no bearing upon the percentage 
of leaves infested. The results are given in Table I. 
Table) I.— Percentage of leaf petioles of Populus deltoides infested with Pemphigus 
populi-transversus, Baton Rouge, La ., July 26, igi6 
Position of branch on tree. 
Number of 
branches 
examined. 
Number of 
leaves 
examined. 
Number of 
leaf petioles 
showing 
galls. 
Percentage 
of leaf 
petioles 
showing 
galls. 
In approximate lower third.. 
5 
222 
54 
24-3 
In approximate middle third. 
5 
441 
117 
26 . 5 
In approximate upper third. 
5 
512 
^37 
26 . 7 
Total. 
15 
L 175 
3 ° 8 
2 $. 2 
DATES WHEN WINGED MIGRANTS (FUNDATRIGENIA) ARE FOUND IN 
GALLS 
At Baton Rouge winged females begin to appear in the galls on 
Populus deltoides at a somewhat earlier date than that recorded for other 
localities. Riley (j, p. 75-16), in connection with his original description 
of the species, in which he gives Missouri, southern Texas, and Colorado 
as localities where this species of Pemphigus occurs, states that the 
winged females are “produced in autumn, sometimes not until the leaves 
have fallen.” Williams (/<?, p. 12) mentions finding winged females, 
“evidently but lately transformed,” in galls at Ashland, Nebr., on 
September 25. At Baton Rouge, in 1916, winged females were found in 
the galls as early as June 1, though a very small percentage of the galls 
contained such individuals on this date. Not until September were they 
present in more than 10 per cent of rather large collections examined. 
1 Three other species of aphids belonging to the subfamily Pemphiginae have been collected from Populus 
deltoides at Baton Rouge. Of these, Pemphigus populicaulis Pitch is the most common, although it is 
much less abundant than is P. populi-transversus . The two other species, found only occasionally in 
galls which they form on the leaves, have not been identified. 
