Pests and diseases
Those affecting ornamental trees can be
divided into three main classes: disease due to bacterial
or fungal action, damage caused by insects and damage
caused by animals (including birds). Of the first, the
most seriously affected trees are members of the rose
Bacterial canker attacks cherries and plums. It is associated with the oozing and dripping of gum from branches or the trunks. Some control can be obtained by pruning out branches affected.
Silver-leaf also affects plums, cherries and apples in particular and occasionally thorns and laurels. The leaves take on a silvery appearance and on a branch that dies a purplish-mauve fungus arises. This should be cut out and burned without delay.
Fire blight may attack pears, hawthorns, rowans, whitebeams and
pyracanthus. Whole shoots in leaf go brown, as if burned,
and die. If this is found, the Ministry of Agriculture,
Fisheries and Food must be notified at once. The most
serious `killer' fungus is the honeyfungus. It occurs
generally on ground that has been woodland which has
been cleared with the stumps or many large roots left
in the ground. Root-like growths, resembling boot-laces
spread through the soil and infect a healthy tree, which
is eventually killed and should be removed. From the
ground around it, toadstools may, but do not always,
arise. They are pale yellow, the gills on the underside
running a little way down the stalk, which carries a
collar-like ring around it. There is no known cure.
It attacks conifers.