The role of antagonists in the chemical control of Fusarium oxysporum f. sp. narcissi

Abstract

Treatment of narcissus bulbs with methoxy ethyl mercury chloride, pimaricin or thiram provided control of basal rot and primary root rot, caused by Fusarium oxysporum f. sp. narcissi and secondary root rot and ‘skin disease’ caused by F. oxysporum ff. spp. A similar treatment with formal in was only effective against basal rot and root rot. Newly formed roots of bulbs treated with the mercurial, pimaricin or thiram became more heavily colonized by Penicillium and Trichoderma spp. than those of untreated or formal in-treated bulbs. Especially P. janthinellum and T. viride appeared to protect the roots against the pathogens. These fungi were found to be antagonistic to F. oxysporum f. sp. narcissi and F. oxysporum ff. spp., both in experiments in vitro and in vivo. A synergism between P. janthinellum and thiram was observed with respect to inhibition of mycelial growth of F. oxysporum f. sp. narcissi in vitro and to control of root rot and basal rot in vivo. In vitro, similar effects were found for pimaricin and organic mercury. Pimaricin was found to stimulate the production of antibacterial metabolites by Cylindrocarpon destructans in vitro. In the field, a synergistic effect was observed between pimaricin and C. destructans with respect to control of basal rot.