Pecan trees.
Phylloxeras are tiny, 1/10 to 1/5 inch long, cream colored to pale yellow insects that resemble aphids but lack cornices. They have sucking mouthparts, which feeding stimulated the plant to produce galls on the leaves, stems, and nuts. The phylloxera reproduce inside the galls. There are 3 species on pecans in Oklahoma .
Pecan phylloxera produces a large green gall on stems, twigs, petioles, midribs, and nuts.
Pecan leaf phylloxera produces small, ovoid to globular, next to the midribs or secondary veins of the leaflets, open on the ventral surface of the leaf. They are evenly green on the top and often reddish beneath when first formed.
Southern pecan leaf phylloxera produces small galls, round and flattened, between the secondary veins on the leaf surface, open on the ventral surface, and show a reticulated pattern on their surface. The opening is marked by dense, short, white hairs.
Symptoms generally appear from June - July in Oklahoma and are characterized by warty-like galls on pecan leaves. The pecan phylloxera, which attacks pecan shoots, and fruit can destroy an entire nut crop and severely weaken and disfigure limb and shoot growth. The weakened and infected shoots tend to sap the tree's vitality and reduce subsequent production.
The timing of control measure is critical for all three species of phylloxera. Trees with infestations the previous year and those trees in the immediate vicinity of previously infested trees should be sprayed. Beneficial insects appear to have a significant impact on phylloxera populations and should be preserved as much as possible.