By bacteria. mushrooms or animal pests trigger pathological growths and swellings Scroll, Buds, stems, blossoms, Roots and fruits of a host plant. At the Rebstock you can by aphids. gall midges. gall wasps, Gall mite and psyllids (see picture). The insects and / or the laid eggs or the hatched larvae indicate substances with a high proportion tannic (Gall tannic acid) to the affected plant site, which characteristically change the surrounding plant tissue. There are a wide variety of forms of bile, each pest causes a characteristic bile shape that enables identification. The damage pattern manifests itself very differently depending on the pest causing the pox-like bumps on the top of the leaf in green, reddish, brown or sulfur yellow (in the case of the gall mite), by lenticular galls (in the case of the gall mosquito) and bag-like bile (in the case of phylloxera). In phylloxera, the biliary body is on the underside of the leaf and the opening on the top of the leaf.
The galls consist of several layers of small, thin-walled cells that are rich in proteins, Starch and oil are and serve the diet. Larger, thick-walled cells that tend to lignify give the bile its strength. The growth of the bile can be attributed either to the enormous swelling of individual cells or to accelerated cell division near the site of the attack. The bile also provides a protective shell for the pest as it feeds on the plant. The most conspicuous galls are caused by insects, which penetrate the plant tissue when they lay their eggs. The enlargement of the surrounding tissue is then caused by secretions from the eggs or from the hatched larva. The vine lice appearing at the roots also cause reactions of the vine through their tapping in the form of growths, which as Nodositäten (with young roots) and tuberosities (on older roots).
Pictures: LWG Bayern