Plum trees (Prunus domestica) are an easy-to-grow fruit tree that is highly tolerant of wet soils common in winter. The late-blooming trees have the advantage of avoiding bud damage from spring frosts. Plum trees have few pest- and disease-related problems. However, a number of potential plum pests target the foliage of the tree. Good pest management starts with a knowledge of possible problems.
Autumn webworm (Hyphantria cunea) is a potential leaf pest of plum trees. Adult webworms are light grey moths and their larvae are light grey or brown, hairy caterpillars with orange and black spots. The larvae feed on the foliage areas between the veins and create colonies on the ends of branches. Webworm damage is most evident from the middle to the end of summer. Management includes pruning and destroying infested tree branches and twigs. Chemical control options include the application of spinosad or Bacillus thuringiensis.
Cankerworm (Alsophila pometaria) larvae are major leaf eaters on plum and other fruit trees. The upper body of the larvae is green and there are three white stripes and one yellow stripe on both sides of the body. There are three pairs of prologs on the larvae and the worms often use the posterior legs to stand upright. Cankerworms skeletonise the leaves by creating deep holes with their extensive feeding. For control, prune and destroy infested tree areas. For trees with severe infestations, use spinosad or Bacillus thuringiensis.
A number of caterpillar species are classified as green fruitworms. Green fruitworms are light green in colour with a white stripe on each side and a thin stripe on the back. Green fruit worms eat the foliage and often tie the leaves loosely together with their silk. As populations of green fruitworms on trees grow, the pests start to eat fruit as well, causing scarring and distortion. Use insecticides such as spinosad and Bacillus thuringiensis for control.