Term for cancerous, scabby and elongated deformities (tuberous = tumour-like), the formation of which is induced on the old (2 to 3 year old) roots when attacked by phylloxera. They are much more dangerous than nodosities (tangles only on young roots). In the European grape varieties of the species Vitis vinifera (but also all other non-resistant species), the tuberosities penetrate through the medullary canals of the root to the central vascular system. Either already through this or through later invading secondary pathogens such as bacteria or fungi, the root is so severely damaged that it dies within one to two years from the point of infestation. The consequence is a considerable reduction of the root mass and consequently a reduced nutrient and water uptake. In the early stages, this leads to stunted growth and later to the death of the vine. Even a few grape aphids can cause dramatic damage to vineyards due to the devastating consequences of this infestation.