Mushroom Virus X (MVX)

Mushroom Virus X (MVX) is easily transmitted within mushroom crops. Find out more about the virus, its visible symptoms and what steps you can take to control it and prevent it from reoccurring.

Originally authored by Helen Grogan (Teagasc) and Richard Gaze.

Mushroom Virus X was first discovered on British farms in the late 1990s. It reached a peak in the early 2000s and was a major factor in the many farm closures that followed. While there are ways to control the disease, outbreaks still pose a threat to mushroom crops.

We don’t know a lot about the origin and nature of MVX, but here’s what we do know:

• Transmission can take place at any point in compost preparation and cropping
• The major sources of potential infection are from infected mushroom spores and mycelial fragments from fully spawn-run bulk phase 3 compost and uncooked-out crops at emptying
• It’s transmitted by anastomosis, the naturally occurring connections between infected and healthy mycelium in the mushroom
• There is no external carrier of the disease
• Even a tiny infected area is enough to transfer the disease to healthy mycelium. The rate of movement of the virus from the point of infection is at least 2.5 m (5 m diameter) by the first flush

Learn about the symptoms of MVX, so you can identify the warning signs in your crop. The two main things to look out for are pinning disruption and development of brown colouration.

Find out how to diagnose MVX and how to prepare and package a sample if you suspect an outbreak. We’ve also listed current hygiene recommendations for preventing and controlling the spread of the virus.

© John Peeters