Insect identification > Homoptera > Aphids > Grape phylloxera

Grape phylloxera


The grape phylloxera (Phylloxera vitifolioe Fitch). - This aphid is a native of America and attacks the grape. Native American vines, however, are resistant to its work to a considerable degree, so that injury to them is not serious. The European grape (Vitis vinifera) on the other hand, is very susceptible to its attacks and, when the phylloxera reached Europe about 1860, it became very destructive, causing the loss of over 2 million acres of vineyards before any successful checks to the insect were discovered.

The insect lays its eggs, one per female, on old wood of the grape in the fall, and these eggs hatch the following spring into tiny lice which locate on the upper surface of the young leaves and begin to suck the sap. This causes the leaf to become depressed at each place where a louse is at work, so that galls projecting from the under surface are soon produced, in which the insects live.

Upon becoming full-grown these aphids lay eggs in the galls and the young which hatch from them pass to other parts of the leaves and produce galls of their own. This process continues through the summer but in the fall the young desert the leaves and work down to the roots and rest until the following spring. Then they attack the roots, forming swellings, which on young rootlets stop their growth and on the larger ones cause decay which spreads around the root and kills it beyond that point.

During the latter part of this second season some winged forms are produced and these make their way up to the surface of the ground and migrate to other vines where they lay eggs. These produce both male and female aphids and each female lays a single fertilized egg which winters over.

This 2-year life and the production of leaf galls are not always necessary to the continued existence of the insect, however. The root form generally goes on, brood after brood, particularly on the European grape, without the formation of leaf galls; and while young from the leaves may probably pass to the roots at any time during the summer, the migration of root forms to the leaves is unknown.

Apparently, then, the life history just outlined applies to American varieties of the vine, but in the case of the European species, while the aphids may pass to the roots, they do not usually, at least, seem to migrate in the reverse direction, the insects which come from fertilized eggs passing directly to the roots. Root forms may spread to other plants through the soil.