The pecan phylloxera is an insect related to Aphids. It causes galls on pecan and hickory trees. The galls initially appear as yellowish-green swellings on the leaves, shoots, and nuts. The greenish galls which average 1/8 to one inch in size; weaken the leaves and branches that they are on to the point that the branch die-back may occur.
Phylloxera eggs are laid in the fall and they over-winter on tree branches. In the spring, juveniles emerge from the eggs and begin feeding on the new, tender foliage. As the females feed, they inject a toxin into the plant tissue, causing the gall to develop. Quickly, the gall grows and envelops the feeding insect, at which time the insect lays the next generation of eggs, which emerge from the galls as winged insects in late May and early June. The most damaging period for pecan and hickory trees is when the first generation feeds on new tender growth.
Recommended Steps to Control Phylloxera
Once the gall is formed, there is no way to eliminate the balls or control the insect inside it. Branches and leaves that fall to the ground should be collected and removed.
During the growing season, at the first sign of the first-generation of Phylloxera, spray the tree with Take Down Garden Spray, to help prevent feeding and laying of the second generation of eggs.
In the fall, the tree should be sprayed with Horticultural Oil Insect Spray, ensuring a good coating is applied to all the branches and the trunk. This prevents the over-wintering of the eggs and other insects on the bark.
The following spring, before bud break, repeat spraying with Horticultural Oil. As the leaves start to form, the tree should be sprayed again with Take Down Garden Spray, before the insects feed on and enter the leaves to begin forming the galls.