Phylloxera

http://www.oardc.ohio-state.edu/grapeipm/insects_attacking_grape_foliage.htm

Phylloxera. This small aphid-like insect has a complex life cycle that involves survival on the roots throughout the year, and on the leaves during the growing season.  The sequence of events in the life cycle is different for the foliar and root forms of this insect.  The foliar form survives the winter as an egg under the bark of the grapevine.  Asexual, wingless forms hatch in the spring and crawl onto the new leaves, where they develop galls.  Young crawlers settle on the upper surface of immature leaves, causing galls to form on the under surface of the leaves.  The only opening in a gall is to the upper leaf surface.  Once mature, the female begins to lay eggs within a gall.  Nymphs hatching from these eggs crawl to new leaves at shoot tips, settle on the leaves, and form new galls.

In the case of the root form of grape phylloxera, the insects overwinter as immature forms on the roots.  These forms mature in the spring and produce eggs that hatch into nymphs.  The nymphs then start new galls on the roots.  Winged forms develop in the spring, summer or fall and emerge from the soil to lay eggs on stems.  These eggs hatch and produce the true sexual forms that produce the overwintering eggs laid under the bark.  Several generations of each form of phylloxera may occur each season.  Although the two forms behave differently, both belong to the same species of phylloxera that occurs on the leaves and roots of grapes.
Denisa Ollomani