Tree diseases and infestations come and go but when is a local concern an epidemic? We know the emerald ash borer is an epidemic. We know maple decline is an epidemic as are beech bark disease and oak wilt but what about the insect you found yesterday? Researchers at Newcastle University are trying to find the answer.
They said, "Predicting and controlling disease spread is incredibly difficult because of the interaction of all the different components involved. It's not just about the type of tree or the hardiness of the disease, it depends on the environment - temperature, humidity, wind speed, the types of trees planted nearby and how close they are.
Finding a disease or pest doesn’t mean there will be an outbreak. Things like weather can kill the pest before it becomes a problem.
They developed mathematical models to mimic the spread of disease under different conditions. Their findings, published in Ecological Modelling, have been able to highlight a 'critical transition' period between two phases: local confinement (the time when the disease is contained and not a threat) and an epiphytotic outbreak. Identifying this critical transition point would result in more informed management system for policy makers.
A key indicator is species mix. "The homogeneous nature of today's woodlands allows the rapid spread of pests and diseases and is where we are most likely to see an outbreak."
— Pat Kerr