Phlloxera are tiny, yellowish insects that suck sap from the underside of leaves, particularly on oak species, producing tiny, irregular brown and yellow spots. Damage is primarily aesthetic and is not serious. Either tolerate this pest or apply insecticidal soap to the Underside of affected leaves before they become severely spotted.

Gall on hickory (Carya) caused by phylloxeras (Hemiptera)	Gall on hickory (Carya) caused by phylloxeras (Hemiptera)
Gall on hickory (Carya) cut open and showing the cause: phylloxeras (Hemiptera)	Close-up of phylloxeras (Hemiptera) inside a gall on hickory (Carya)
Close-up of phylloxeras (Hemiptera) inside a gall on hickory (Carya)	Close-up of phylloxeras (Hemiptera) inside a gall on hickory (Carya)
Close-up of phylloxeras (Hemiptera) inside a gall on hickory (Carya)	Phylloxera (Hemiptera) are a tiny insects that sometimes feed on roots but can also cause leaf galls, as on these grape leaves (Vitex)
Close-up of galls on grape leaves (Vitex) caused by phylloxera (Hemiptera)