In more than 45 years of tree work across Kent and the South East, we have seen how quickly a single infection can change the condition of a tree. Recognising disease is part of the job, not an optional extra. Whether you are thinking about a career in arboriculture or brushing up before an assessment, these are the problems you are most likely to meet on British sites.
Ash Dieback
Caused by the fungus Hymenoscyphus fraxineus, ash dieback has spread through woodlands across the country since it was confirmed here in 2012. Look for blackened leaves wilting early in the season, diamond-shaped lesions where branches meet the stem, and crown thinning that works from the top down. Infected ash turns brittle and behaves unpredictably under load, which makes it one of the riskier species to work on. No one should climb a heavily affected ash without a proper assessment first.
Honey Fungus
Honey fungus, or Armillaria, attacks the roots and lower trunk of a wide range of species. The clearest signs are honey-coloured toadstools at the base in autumn, a white fungal sheet beneath the bark, and black bootlace strands running through the surrounding soil. It travels underground between hosts, so one infected tree often points to a wider issue across the garden or site.
Bleeding Canker of Horse Chestnut
Dark, sticky fluid seeping from splits in the bark is the giveaway here. The bacterium Pseudomonas syringae pv. aesculi is usually responsible, and over time the cankers can girdle the stem and bring on crown dieback. Plenty of trees hold on for years, so felling is rarely the first answer.
Phytophthora Root Rot
Phytophthora species thrive in wet, poorly drained ground and rot the root collar. Above ground you will notice sparse foliage, undersized discoloured leaves and slow decline. The soil is where the trouble starts, which is why drainage work often forms part of the remedy.
Learning to Spot Disease on Site
Photographs in a textbook only take you so far. Our courses put you in front of real trees in real conditions, where you learn to read the whole tree rather than one symptom. If you are ready to begin, get in touch and we will talk through the right route for you.