Among more recent threats was Chalara disease of ash (Hymenoscyphus pseudoalbidus), according to consultant, writer and lecturer David Lonsdale.
This may not yet be in Britain, he told a recent seminar at Barcham Trees. But incidence of branch dieback of ancient ash pollards north of the UK was moving both south and west, he added.
Meanwhile, Phytophthora lateralis, found for the first time in Britain on Lawson cypress at Balloch Country Park in West Dunbartonshire, was also known to attack the Pacific yew (Taxus brevifolia). This was a close relative of the common yew (Taxus baccata), which could become a potential target.
Lonsdale flagged up other pests, including chronic oak decline and oak mildew. Ceratocystis fimbriata f. platani, a vascular wilt disease, presented a serious threat to some of the earliest planes.
American sweet chestnut (Castanea dentate) had been devastated by chestnut blight (Cryphonectrica parasitica), a fungus.
Once trees were attacked, they often died quickly. "We do not want this in the UK", Lonsdale warned.