Integrated control of Fusarium damping-off in red pine seedlings with the ectomycorrhizal fungus Paxillusinvolutus and fungicides

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Abstract
Damping-off caused by Fusariumoxysporum Schlecht. in red pine (Pinusresinosa Ait.) was significantly reduced when seedlings were treated with either of two fungicides (benomyl or oxine benzoate) concomitantly with the ectomycorrhizal fungus Paxillusinvolutus (Batsch.) Fr. compared with inoculation with P. involutus alone. Both fungicides at concentrations of 10 ppm and above significantly reduced spore germination and germ-tube length of F. oxysporuminvitro. On the other hand, invitro growth of P. involutus mycelium was not affected by the fungicides at concentrations up to 1000 ppm. The growth of P. involutus was, however, significantly reduced by the two fungicides at 5000 and 10 000 ppm. Inoculation of red pine seedlings with P. involutus was effective under growth chamber and greenhouse conditions in reducing the incidence of damping-off induced by F. oxysporum. When benomyl and oxine benzoate were applied in combination with P. involutus, seedling mortality was not observed. Oxine benzoate was phytotoxic and inhibited mycorrhiza formation by P. involutus at the recommended dose. Benomyl, on the other hand, had no inhibitory effect on seedling growth and stimulated ectomycorrhiza formation either by a naturally occurring mycorrhizal fungus or P. involutus in the greenhouse. The concept of incorporating integrated biological and chemical treatment for controlling Fusarium damping-off of red pine seedlings is suggested.