How to Manage Pests

Grape phylloxera—Daktulosphaira vitifoliae

Identification

Phylloxera are tiny yellow soft-bodied insects that feed in groups on roots especially in summer and fall. They are oval and less than 0.10 inch long; a hand lens is required to see them.

Life cycle

Phylloxera overwinter on roots as small nymphs. In spring these nymphs feed and mature. The mature forms, which are females only, deposit eggs by asexual reproduction, giving rise to several generations throughout summer and fall. Some phylloxera crawlers leave heavily infested roots and travel on the soil surface or through cracks to infest other portions of the roots or roots of other vines. At the end of September, some begin to hibernate, and by mid-December all forms hibernate. Where soil temperature does not go far below 60°F, however, feeding and reproducing forms may be found all winter. In summer and fall some winged migratory forms may be produced, but in California they are unable to reproduce and are not a factor in the dissemination of the insect. There are about five generations a year.

Damage

Phylloxera cause a premature yellowing of leaves and stunted growth. Root tips are swollen with yellow brown galls. Roots may be dead or dying.

Symptoms

There are no satisfactory controls available once vines are infested. Good irrigation and fertilizer practices help offset damage to roots. Use resistant rootstocks.

Phylloxera colony

Clubbing of root tip

Damaged root (top)