Tree pests and diseases follow a predictable pattern called the pest and disease cycle.
The further through the cycle the pest or disease progresses, the worse the outbreak, and the harder it is to eradicate, contain, or mitigate the impact.
Where do you interact with the cycle?
Transport
The cycle starts with the transport of a pest or disease over long distances to a new location.
This can occur naturally, for example on wind currents, but is often aided by people trading and moving plants and soil.
Pests and diseases often have special survival strategies that keep them alive during these phases with hostile conditions.
Transport leads to introduction, and can restart the cycle during the establishment and spread steps.
Introduction and establishment
At the end of the journey, the pest or disease is introduced to a new area.
Introductions to unsuitable areas may fail to establish. Repeated or larger introductions make establishment more likely.
And if the host, habitat, and climate conditions are suitable, the pest or disease can build up larger populations.
Spread
Once established, pests or diseases start to spread, locally at first.
Spread is helped by wind, rain, livestock, wildlife, people, trade, vehicles and/or equipment.
The speed and intensity of spread depends in part on:
- the characteristics of the pest or disease
- how many hosts it can infect
- how widespread and how susceptible they are
The biggest economic, environmental, and societal impacts will be observed at this stage.
