Observations on the parasitism and control of Armillaria mellea

Armillaria root disease has been known since 1874. Until recently, the fungus was believed to attack roots only through wounds. Thomas (1934), however, has shown in an interesting paper that Armillaria mellea (Vahl.) Quel, penetrates the roots of healthy plants in the absence of wounds. His paper gives such a full review of the literature connected with the parasitism of this fungus that repetition would be superfluous here. Thomas gives a detailed description of the entry of Armillaria rhizomorphs into various roots and tubers. He compared the reaction in the tissues of resistant and susceptible plants but, unfortunately, could not formulate any control measures as a result of his observations. Wallace (1935) has reviewed the control measures employed up to date against the disease. Armillaria, however, has caused, and is still causing, serious losses to tea in Nyasaland, although thorough stumping and root clearing have been employed as much as is practicable and economic in the opening up of new tea gardens. The author has been forced to the conclusion that control measures as advocated up to date are very far from satisfactory.