Daktulosphaira vitifoliae is responsible for symptoms that are not usually lethal on American grape varieties. The galls caused by the bites of this insect are visible on the underside of the leaves (Figures 1 to 4), although chlorotic lesions are visible on the blade (Figures 5 and 6) They are present throughout the active growth phase. of the vine, and are reddish-green in color. Affected leaves often have reduced growth which results in bad wood growth. In case of heavy infestation, the larvae can settle on the other herbaceous parts of the plant (petioles, tendrils).

At the level root , the presence of nodules linked to insect bites is also observed on the rootlets; their frequency varies more or less depending on the species of Vitis considered. On the European variety, Vitis vinifera , aerial attacks are considered exceptional. The attacks occur mainly at the level of the roots which have nodules on the rootlets and tuberosities on the older roots.

 

The nodules (Figure 7 and 8), initially yellow in color, turn brown and more or less necrosis. There is a characteristic deformation in the beak of birds.
Tuberosities, due to hypertrophy of cortical tissues, are characterized by a capsule shape, and the presence of the female and her egg-laying.

 

It is at their level that the root cracks will occur, causing the decline of sensitive vines. Indeed, these cracks facilitate the entry of soil microorganisms responsible for root lesions. These will progress to the cambium, which will cause the death of the distal part of the roots.

 

There will be a cessation of nutrient transport by the bast. If symptoms affect the main root, the vine will inevitably wither 2 to 5 years after infestation.

Let us add that in the affected plots, phylloxera is transmitted step by step to neighboring plants (oil stain symptom).