Phialophora cyclaminis is a virus which causes a somewhat rare vascular disease presenting the same kind of symptoms as Fusarium oxysporum var. cyclaminis: part of the plant droops suddenly, turns yellow and then perishes completely.
Plants must be kept off the ground and sources of stress avoided, for it is this which encourages attack by this fungus. Once the process of infection is under way, all countermeasures are unavailing.
Fungi of the genus Phialophora belong to the order Moniliales of the class Adelomycetes. They are of the Dematiaceae family, and are septate fungi (their mycelia are divided by partitions); their reproduction is asexual.
Phialophora cyclaminis is the species which attacks cyclamen. Like Fusarium oxysporum var. cyclaminis, it causes a disease known as Trachaeomycosis or vascular disease. Unlike Fusarium disease, though, this disease is encountered very seldom.
Optimum temperature for growth of Phialophora cyclaminis is between 15ºC (59ºF) and 18ºC (64ºF): it is, therefore, a fungus which develops particularly in the spring months, a disease of cool periods.
It is a systemic fungus. It is present in the soil and its mycelium penetrates the plant through the root system and develops there.
Invasion of the roots takes place either through damaged and wounded sites or actively, through healthy tissue. Once the vascular system of the plant is invaded the circulation of sap is hampered.
Obstruction of the vessels causes progressive perishing of the plant.
The leaves turn yellow, and part of the cyclamen droops. What is happening is that some parts of the plant are getting less and less water and nutrients.
The first signs are often restricted to half of a leaf, or half of the plant.
Often the older leaves are the first affected, and the symptoms then appear higher and higher up the plant. The general tendency is for this lack of nutrition to spread throughout the upper parts of the plant, which appears more and more withered.
The roots themselves turn black and the cyclamen perishes entirely.
Phialophora cyclaminis lasts for many years in the soil, in the form of conidia, sclerotia or vegetative resistant spores (chlamydospores). Transfer and mixing of contaminated soil or compost, washing with contaminated water, and reuse of water are all possible means of infection, though not the only ones; humans too are implicated, or their footwear is.
Both the bacterium, Erwinia carotovora ssp. carotovora and the fungus Fusarium oxysporum var. cyclaminis also cause vascular diseases; and it is not always an easy matter to determine precisely which pathogen is at the bottom of an infectious onslaught.
However, in the case of Phialophora the base of the cyclamen’s leaves do not show brown staining, as they do with Fusarium; while the stalks and buds, on the other hand, are softened.
It is highly possible that Phialophora may have infected a cyclamen following an attack by Fusarium; so that it is not rare to find both pathogens in the vessels of the same plant.
The source could also be an irrigation problem, either too little or too much water, or too high a concentration of salts in the feed solution.
Disinfection of compost gives the best results.
Once infection is under way there is not really anything that can be done. The following systemic products can however be watered on as a precaution.
The constant development of the regulations and homologations of phytosanitary treatment products, and the differences in regulations according to each country make it impossible for us to include updated information on homologations. Each producer will have to contact his local plant protection bureau to obtain the latest updates concerning the regulations and use of phytosanitary products. We strongly advise testing beforehand on a plant sample in order to measure the chemical’s activity (establishing the dose) and any effect on the plant (plant poisoning).
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