Phylloxera - Biology of Phylloxera

Biology of Phylloxera

The phylloxera louse has a complex life-cycle of up to eighteen stages that is divisible into four principal forms: sexual form, leaf form, root form, and winged form.

The sexual form begins with male and female eggs laid on the underside of young grape leaves. The male and female at this stage lack a digestive system, and once hatched, they mate and then die. Before the female dies, she lays one winter egg in the bark of the vine's trunk. This egg develops into the leaf form. This nymph, the fundatrix (stem mother), climbs onto a leaf and lays eggs (via parthenogenesis) into a leaf gall she creates by injecting saliva into the leaf. The nymphs that hatch from these eggs may move to other leaves, or move to the roots where they begin new infections in the root form. In this form they perforate the root to find nourishment, infecting the root with a poisonous secretion that prevents it from healing. It is this poison which eventually kills the vine. This nymph reproduces four to seven more generations of eggs (which are also capable of parthenogenetic reproduction) each summer. These offspring spread out to other roots of the vine, or to the roots of other vines through cracks in the soil. The generation of nymphs that hatch in the autumn hibernate in the roots and emerge the following spring when the sap begins to rise. In humid areas, the nymphs develop into the winged form (otherwise, they perform the same role without wings). These nymphs start the cycle over again by either remaining on the vine to lay male and female eggs on the bottom side of young grape leaves, or flying to an uninfected vine to do the same.

Many attempts have been made to interrupt this life cycle to eradicate phylloxera, but the louse has proven to be extremely adaptable, as no one stage of the life cycle is solely dependent upon another for the propagation of the species.