Trees can be attacked by a variety of bacteria, viruses and fungi. These organisms are usually too small to see, which can make identifying them very difficult for homeowners.

Grande Prairie's northern climate often works in our favour, killing diseases and preventing them from overwintering. However, every spring new plants arrive in garden centres and these can carry diseases. Some diseases are host specific, some alternate seasonally between two plant hosts, and others are generalists and affect a broad range of different plants.

They can spread by wind and insects, as well as through human activities.