By bacteria. mushrooms or animal pests triggered morbid growths and swellings Scroll, Buds, stems, blossoms, Roots and also fruits of a host plant. At the Rebstock you can go through aphids. gall midges. gall wasps, Gall mite and psyllids (see picture). The insects and / or also the deposited eggs or the hatched larvae give substances with a high proportion tannic (Gallic acid) to the affected plant site, which change the surrounding plant tissue characteristically. Galls exist in great variety of forms, each pest causes a characteristic bile shape, which allows identification. The damage manifests itself very differently depending on the causative pest by smallpox-like elevations on the upper leaf surface in green, reddish, brown or sulfur yellow (in the Gallmilbe), by lentil-like gall (in the Gallmücke) and beuteal galls (in phylloxera). In the phylloxera, the bile body is located on the underside of the leaf and the opening on the leaf top.
The galls are made up of several layers of small, thin-walled cells that are rich in proteins, Starch and oil are used to diet. Larger, thick-walled cells prone to lignification give bile their strength. The growth of bile is either due to the enormous excitation of individual cells or to accelerated cell divisions near the site of attack. Bile also provides a protective shell for the pest as it feeds on the plant. The most prominent bile are caused by insects that invade the plant tissue with the oviposition. The enlargement of the surrounding tissue is then caused by secretions of the eggs or by the hatched larva. The root phylloxera that occur at the roots cause by their puncture also reactions of the vine in the form of growths, which as Nodositäten (at young roots) and tuberosities (older roots).
Pictures: LWG Bavaria