Zur Frage der direkten oder indirekten Schädigung von Rebenwurzeln bei Befall durch die Reblaus (Dactylosphaera vitifolii Shimer)

Is damage of phylloxera infested grapevine roots caused directly or indirectly?Disinfected eggs of phylloxera (Dactylosphaera vitifolii SHIMER) were transferred to rooted explants of Vitis vinifera shoots (cv. Silvaner) reared under sterile conditions. Aerial rootlets which showed injuries in consequence of the insect's infestation proved to be free of microorganisms. lt is concluded, therefore, that damage of grapevine roots is pr imarily due to the activity of phylloxera itself, especially to abnormous growth and disturbance of metabolism in the affected plant tissues. Microorganisms occurring in root galls of naturally growing vines are considered to be secondary parasites or saprophytes