Symptoms of Mushroom Virus X

Find out about the symptoms of Mushroom Virus X, so you can identify the disease in your crop, and help manage outbreaks.

How to identify Mushroom Virus X

At the moment, we know of two main strains or combinations of the virus and their symptoms: MVX-PD (causing pinning disruption) and MVX-BS (causing browning symptoms).

Pinning disruption (MVX-PD)

The core symptom of MVX-PD is disruption to pinning, which delays sporophore production. This delay may affect the whole crop and can range from very short to five days or longer.

Bare patches on the bed are a key sign of severe pinning disruption. The quality of the mushrooms can appear normal, but the delay often leaves farmers with a much smaller yield of crops.

Other signs to look out for, are:

Premature opening
Mushroom distortion
Poor keeping quality
Off-white mushrooms
General yield reduction on top of that caused by bare patches

Brown symptom (MVX-BS)

Another distinct symptom of MVX is discolouration in white mushrooms:

It can range in colour from cream to brown
It sometimes occurs in only one flush
It can affect a few isolated mushrooms or spread to the majority of a flush
The symptom may appear before harvest or after the mushrooms have been picked and cold-stored
Apart from discolouration, affected mushrooms appear healthy, often with no apparent yield loss or pinning disruption
Virus testing has shown that non-symptomatic white mushrooms can still be infected with MVX