Fusarium, the Vanilla Killer: What Can be Done to Stop it?
Dr. Roni Cohen
Newe Ya'ar Research Center, ARO
Ramat Yishai, Israel
Fusarium oxysporum is a large species complex inhabiting cultivated and non-cultivated soils from the artic to the desert. This fungi group can cause significant plant diseases including crown and root rot and damping off but they are most known as causal agents of vascular wilt diseases.
Root and stem rot is a very detrimental disease of vanilla worldwide. In a survey conducted in the most common vanilla growing regions, Fusarium oxysporum was found to be the principal species responsible for the disease. In a microscopy observation of disease plants it was shown that the fungal hyphae is not invading the root vascular system. Thus, the pathogen attacking the vanilla plants should be named F. oxysporum f. sp. radicis-vanillae.
F. oxysporum f.sp radicis attacking annual plants such as melon, cucumber and tomato can be managed by grafting onto resistant rootstocks as a short term solution and breeding for resistance as a long term goal. Moreover, these crops are grown in a short time period and can be grown in other fields with low disease pressure or with an option of soil disinfection between seasons. In vanilla, however, the situation is much more challenging. Vanilla is a monocotyledon plant making grafting onto resistant rootstock almost impossible. The genetic background is very narrow, thus breeding high quality resistant cultivars is very difficult. Vanilla is a perennial crop and its propagation is based on cuttings making usage of disease free propagation material and sanitation of highly important factor for successful crop.
Prochloraz and strobilorin fungicides have shown good results in fusarim crown and stem rot control in tomato and cucumber. In addition, studying the effect of environmental conditions and fertilization on disease incidence and severity may lead to knowledgeable growing practices that may lower disease risks.
Dr. Roni Cohen is a senior researcher in the division of cucurbit research and breeding in the Agriculture Research Organization (ARO), Newe Ya'ar Research Center, Israel. He received his Ph.D. in 1987 from the Hebrew University of Jerusalem, Israel.. His research interests are soil borne fungal diseases and powdery mildew of cucurbits. Roni is involved in introducing grafted plants to the Israeli agriculture as one of the alternatives of methyl bromide soil fumigation.