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 groun