Eucalyptus cloeziana mulch suppresses Fusarium wilt of banana

Fusarium wilt of banana, caused by Fusarium oxysporum f.sp. cubense, is a serious threat to banana production, with no effective treatment. Mulches and oils from Eucalyptus have been shown to inhibit the growth of F. oxysporum, and reduce the severity of Fusarium wilt. Eucalyptus cloeziana leaves contain many compounds commonly found in Eucalyptus as well as a very high concentration of the uncommon compound tasmanone. We applied E. cloeziana mulch, fresh or partially steam distilled, or no mulch as a control, to potted soil, inoculated the soil with F. oxysporum f.sp. cubense and grew susceptible banana plants to test the capacity of the mulch to reduce the severity of Fusarium wilt of banana. Disease severity, analysed by internal corm discoloration, was reduced from 90% in the control to 37% in the treatment with steam distilled mulch.In another experiment, comparison of steam distilled with fresh mulch showed no difference between the two, with a disease severity of 13%, compared to 49% in the control. Mulch (fresh or steam distilled) had no detrimental effects on plants grown without F. oxysporum inoculation. We propose that disease suppression was likely due to tasmanone, as it was the primary oil constituent of the mulches.