Fruit Tree Pests and Disease

Rust Physical Manifestations Leaves show small orange spots. Over time, these spots enlarge and turn red. In late summer, these spots become blisters which burst into spores. Leaves can drop early and dieback can occur.

Rust Prevention & Management Prune and dispose of infected branches in the fall and winter. Try not to plant juniper species and hosts near each other.

Trees & Plants Affected by Rusts Pear, many species of juniper, apples, crabapples, quince and serviceberry are the fruiting trees susceptible to rusts. Mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia are plants susceptible to rusts. 

Rust Causes Pear trellis rust: Gymnosporangium sabinae a fungal disease; Cedar-apple rust: Gymnosporangium juniperivirginianae; Cedar-hawthorn rust: G. globosum; Cedar-quince rust: G. clavipes

Scab Physical Manifestations Leaves start as small, olive-green spots that turn to black. Leaves distort, turn yellow and fall early in summer. Starts on fruit as small, raised dark areas, which become large and corky. Fruits distort, crack and fall too early.

Scab Prevention & Management Rake and dispose of leaves and fruit in the fall since the disease and live in them over the winter. Compost leaves. Avoid watering the top of the tree.

Trees & Plants Affected by Scab It infects crabapples, pear (Pyrus communis) and apples (Malus spp.) Mountain ash (Sorbus spp.), and Cotoneaster (Cotoneaster spp.).

Scab Causes Caused by the fungus Venturia inaequalis.

Fire Blight Physical Manifestations Leaves turn brown and wilt and curl into a candy cane shape. Droplets of ooze can form on twigs. Dark cankers, or lesions, can form. Fruit may be shriveled. The tree might look burned.

Fire Blight Prevention & Management Prune the infected limbs and cut a distance much lower than the diseased area. Remove the pruned branches and dispose of them or burn them. Sterilize tools with rubbing alcohol between cuts. If caught in a later stage (when large areas are affected), consider calling an arborist to manage the disease. They will most likely conduct extensive pruning and apply a chemical or biological control agent.

Trees & Plants Affected by Fire Blight Pome fruit trees. Pear (Pyrus species) and quince (Cydonia) are susceptible; apple, crabapple (Malus species).
Related plants: hawthorn, cotoneaster, mountain ash, and firethorns are frequently damaged.

Fire Blight Causes Bacterium Erwinia amylovora

Black Knot Physical Manifestations Knots start as light brown, warty swellings around 1cm long on new shoots. The knots turn coal black and can encase the whole limb. Boring insects might be seen on the knots. Sometimes, the branch with the knot dies after spores are released in early spring. If the branch lives, the knot keeps getting bigger and produces new spores every spring. The knot can completely encircle and girdle a branch. When this happens, the leaves beyond the gall wilt and die.

Trees & Plants Affected by Black Knot Prunus trees including ornamental, edible, and native plum and cherry trees. Peach, nectarine and apricot are less commonly infected.

Black Knot Causes Apiosporina morbosa (syn. Dibotryon morbosum) fungus.

Black Knot Prevention & Management Prune trees at least 10cm below any visible knot, since the infection can run deep. Dispose of pruned branches in plastic bags or burn them. Prune in spring before new growth to prevent spores from spreading in the wind.

Codling Moth Physical Manifestations Adults are medium-sized (about 3/8 inch long) and light grayish brown. The males have a distinctive band of shiny coppery scales at the end of the wings. Codling moth larva is large (up to ½ inch long), and has a pinkish body with a brownish head. The larvae tunnel towards the apple cores and feed on the seeds before exiting the fruit. Crumbly golden-brown frass (excrement) is sometimes found at the hole where the larva exited the apple.

Trees & Plants Affected by Codling Moth Pome fruit trees. Pear (Pyrus species) and quince (Cydonia) are susceptible; apple, crabapple (Malus species).

Codling Moth Causes Codling moth (Cydia pomonella).

Codling Moth Prevention & Management Keep your garden or orchard regularly clean. Pick up and remove any fallen apples throughout the growing season and after harvest and place them in the trash. Do not throw away apples in places where you also store apples. Inspect your crates and the storage building for cocoons and destroy the insects. Codling moths can be trapped using a tent-shaped plastic or waxed-paper trap, hung in a tree. The most common are “delta” traps or “wing” traps.

Maggot Fly Physical Manifestations Adults are medium-sized (about 3/8 inch long) and light grayish brown. The males have a distinctive band of shiny coppery scales at the end of the wings. Codling moth larva is large (up to ½ inch long), and has a pinkish body with a brownish head. The larvae tunnel towards the apple cores and feed on the seeds before exiting the fruit. Crumbly golden-brown frass (excrement) is sometimes found at the hole where the larva exited the apple.

Trees & Plants Affected by Maggot Fly Pome fruit trees. Pear (Pyrus species) and quince (Cydonia) are susceptible; apple, crabapple (Malus species).

Maggot Fly Causes Codling moth (Cydia pomonella).

Maggot Fly Prevention & Management Keep your garden or orchard regularly clean. Pick up and remove any fallen apples throughout the growing season and after harvest and place them in the trash. Do not throw away apples in places where you also store apples. Inspect your crates and the storage building for cocoons and destroy the insects. Codling moths can be trapped using a tent-shaped plastic or waxed-paper trap, hung in a tree. The most common are “delta” traps or “wing” traps.