Biological control of armillaria root rot

"Armillaria root rot of trees is notoriously difficult to control under urban conditions. Chemical control by cresylic acid formulations shares all the usual problems associated with application of fungicides to the soil or roots and is unpleasant as they are classed as irritants with harmful fumes. The hosts treated may suffer from phytotoxicity. For these reasons, and particularly where children and wildlife are present other methods need to be used. In this study several isolates of Trichoderma harzianum, T. hamatum, T. viride, Chaetomium olivaceum, Phycomyces nitens, and two unidentified mycopathogenic fungi were evaluated as potential biocontrol agents against two isolates of Armillaria mellea. The Trichoderma isolates and a fungus isolated from Shitake mushrooms (Lentinus edodes), probably Dactylium dendroides, grew extensively over the Armillaria colonies restricting and killing the mycelium of the fungus and disintegrating its rhizomorphs. Isolates of T. harzianum, C. olivaceum and the unidentified fungi were also tested on plants in the glasshouse. The roots of potted strawberry plants were infected with hazel billet inocula of the pathogen and treated simultaneously with these moulds. However only one isolate of T. harzianum and C. olivaceum successfully protected the strawberry plants from infection, suggesting that in vitro and in vivo performance may not necessarily be correlated. Field studies on apple trees are now in progress." [Abstract]

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