A Comparative Study of the Effects of Five Chemicals on the Survival of Chlamydospores of Fusarium oxysporum f. sp. <i>narcissi</i>

Abstract

Abstract Formaldehyde is routinely used in hot water treatment for the control of narcissus basal rot (caused by Fusarium oxysporum f. sp. narcissi ) and stem and bulb eelworm ( Ditylenchus dipsaci ). It does not kill all the thick walled chlamydospores of F. oxysporum. Four chemicals were evaluated for their efficacy against F. oxysporum by comparing them with the standard formaldehyde rate. At rates of 0.25% a.i. or more, a glutaraldehyde formulation (Cidex) killed 100% of spores within 160 min. Peratol, a hydrogen peroxide and peracetic acid containing formulation, gave 100% kill after 80 min at a concentration of 0.5%. A thiabendazole formulation (Storite Clear Liquid) killed all the chlamydospores. Decon 90 failed to control the fungus adequately. Formaldehyde (as 0.5% commercial formalin) gave good, but not total, control of the fungus but, at higher rates (2.5%), caused flower malformation and corkiness of bulb base plates. The results suggest that Cidex and Peratol, as they are more effective than formaldehyde in controlling the fungus and less unpleasant to use, may be suitable replacements.