Pests and Diseases of Tree Fruit

Pests and Diseases of Tree Fruit

Including: apples, pears, quinces, cherries, plums, damsons, peaches, almonds, apricots and nectarines

All tree fruit are susceptible to the following pests, diseases and common problems unless otherwise stated.


Aphids (various species)

Pests and Diseases of Top Fruit - peaches Typical symptoms: Leaves and young shoots are infested with pink, green, black or brown aphids. Leaves may be distorted or tightly curled and sticky to the touch. Growth of young shoots may be reduced or distorted.

Prevention and treatment: See Aphids as Garden Pests


Apple canker (Nectria galligena)

This affects apples and pears (also hawthorn and poplar).

Typical symptoms: Twigs and branches show cracks around the base and wrinkled, discoloured, sunken patches. Spurs, shoots and branches may die.

Prevention and treatment: Grow varieties that are less-susceptible to this disease. Avoid poorly drained sites and overfeeding as both conditions will make trees more susceptible to canker. Inspect apple and pear trees regularly and cut out any canker immediately it is seen. Burn diseased wood and paint pruning cuts with Trichoderma paste.


Apple and other capsid bugs (Plesiocoris rugulipennis, Lygocoris pabulinus and others)

Apple, pear, plum and damson are susceptible to capsid bugs.

Typical symptoms: Tattered holes appear in young leaves; fruits are distorted and/or with raised bumps or scabs.

Prevention and treatment: Damage caused by capsid bugs is rarely severe. Little can be done other than to keep trees growing well.


Apple powdery mildew (Podosphaera Ieucotricha)

This affects apples and pears.

Typical symptoms: Powdery white coating on leaves, flowers and twigs.

Prevention and treatment: See How to Treat Common Plant Diseases


Apple sawfly (Hoplocampa testudinea)

Apple sawfly affects both apple and pear trees.

Typical symptoms: The damage caused by sawfly larvae is similar to that of the codling moth but occurs earlier in the season. A large cavity is eaten in the fruit; this cavity is filled with the droppings of the larvae, known as “frass”. The fruit may fall early. Fruit that does mature may show a characteristic ribbon scar.

Prevention and treatment: Remove and compost all fruits that fall early. If there is a regular severe problem, spray with derris liquid as directed on the container, usually at petal fall.


Apple scab (Venturia inaequalis); pear scab (Venturia pirina)

These affect apples and pears respectively.

Typical symptoms: Dark greenish-brown blotches on leaves and fruit. When infection is severe, leaves may fall early and fruit become cracked or corky. (Note that adverse soil conditions can also cause black blotches on pear leaves.)

Prevention and treatment: Grow resistant varieties, especially in wet areas. Do not grow susceptible plants in damp areas or close to water. Keep the tree open by pruning to allow good air flow. Collect up all fallen leaves in the autumn or run a mower over them to speed up decomposition. Prune out infected twigs, which will show blistered swellings. These measures will help reduce reinfection in spring.


Bacterial canker (Pseudomonas morsprunorum)

This affects plums, cherries and peaches.

Typical symptoms: Leaves have small round “shot” holes. Shallow depressions (cankers) appear on branches, often on one side of the branch only. If the canker girdles the branch, growth beyond it will die.

Prevention and treatment: Do not grow Victoria plum, which is particularly susceptible. Avoid wounding trees when staking and tying as the disease enters through wounds. Prune out and burn or dispose of diseased wood, cutting back into healthy wood as soon as it is noticed. Paint pruning cuts with Trichoderma paste. If the disease persists, spray with Bordeaux mixture in late summer and early and mid-autumn.


Bitter pit (calcium deficiency)

This affects apples, especially ‘Bramley’ and ‘Newton Wonder’. It is most frequent on young, vigorously growing trees.

Typical symptoms: The fruit becomes pitted and brown spots appear scattered through the flesh, which may also show “glassiness” — a translucency. These symptoms are caused by a shortage of calcium in the fruit, but this is rarely due to a calcium deficiency in the soil, rather an imbalance of calcium with other elements.

Prevention and treatment: Check the pH of the soil and add lime if it is much lower that 6.5. Do not overfeed with nitrogen or potash, both of which can reduce the availability of calcium. Maintain a regular supply of water to the tree by improving soil structure, mulching and watering when necessary. When bitter pit is a recurring problem, use the fruit as soon as it is ripe or preserve it by freezing or bottling. The condition develops further in stored apples.


Brown rot, blossom wilt, spur blight and wither tip (Sclerotinia fructigena; S. laxa)

This affects most tree fruit (also ornamental Prunus species).

Typical symptoms: Blossom wilts; fruit spurs may die after flowering; fruit develops soft brown patches with concentric rings of white pustules. Dehydrated fruit will hang on tree all winter.

Prevention and treatment: The fungus infects through wounds caused by weather, birds, insects and rubbing branches. Prune well, thin the fruit and try to repel birds. Remove all mummified fruit; prune out all infected wood, burn or dispose of it and treat the cuts with Trichoderma paste.


Bullfinches

Typical symptoms: Buds removed in winter; poorblossom and bare lengths of stem in spring.

Prevention and treatment: see Garden Pests and Diseases – Barriers and Traps


Codling moth (Cydia pomonella)

Apple and pear are susceptible to codling moth.

Typical symptoms: Codling moth caterpillars tunnel to the fruit’s core; it may be rendered inedible. The caterpillar usually leaves before the damage is discovered as there is generally no obvious sign of its presence on the outside of the fruit.

Prevention and treatment: Encourage bluetits into the garden as these are effective predators of the codling moth. To protect fruit, hang pheromone traps in the trees to catch male moths (see Garden Pests and Diseases – Barriers and Traps). The traps should be in place from late spring to late summer, or during early autumn in a dry year. However, traps alone may be sufficient to control coddling moths, in which case use them to indicate the presence of the moths so that spraying can be timed effectively: the young caterpillars must be killed before they can enter fruit. To ensure this, spray with derris seven to ten days after the moths are caught.


Coral spot (Nedria cinnabarina)

This affects all top fruit.

Typical symptoms: Masses of bright pink pustules appear on dead wood. Branches may die back.

Prevention and treatment: See How to Treat Common Plant Diseases


Fireblight (Erwinia amylovora)

This affects apple and pear trees (also other related ornamentals).

Typical symptoms: Dead blossoms and dark brown leaves hang from affected branches giving the appearance of having been scorched by fire. A mature tree can be killed in as little as six months.

Prevention and treatment: Pear varieties that flower in summer are much more prone to infection than those that flower early. Prune out infected branches immediately, cutting at least 45cm (1-1/2ft) into the healthy wood. If this procedure does not save the plant, dig it out and burn or dispose of it.


Honey fungus (Armillaria mellea)

This affects all top fruit.

Typical symptoms: Trees die suddenly. The bark near the base of the trunk pulls away easily, revealing a white sheet of fungal growth of mushrooms.

Prevention and treatment: See How to Treat Common Plant Diseases


Peach leaf curl (Taphrina deformans)

This affects peaches, almonds and nectarines.

Typical symptoms: Red blisters appear on leaves in early summer; infected leaves turn brown and fall prematurely. Regular attacks will reduce the vigour of the tree.

Prevention and treatment: Do not plant susceptible trees in cool, damp situations, especially near a pond. Small trees and those grown against a wall can be covered with a structure to keep the rain off. This will prevent the transfer of disease spots from the bare wood to the developing leaves and it should be kept in place from early spring until all the leaves have developed. Where practical, remove and burn or dispose of affected leaves as soon as they are noticed. Spray with Bordeaux mixture as directed on the container, usually in mid- to late winter, just before leaf fall. If regular spraying is required, consider growing species of top fruit other than peaches, almonds and nectarine and instead concentrate on those not prone to this disease.


Pear and cherry slugworm (Caliroa cerasi)

This affects pear and cherry along with almond, hawthorn, rowan and related trees and shrubs.

Typical symptoms: The upper surface of the leaves is grazed so that only the skeleton remains. Small, shiny black, slug-like larvae may be seen.

Prevention and treatment: Where pests are seen, remove them by hand. If this is not practical, spray with derris or insecticidal soap. In winter, lightly cultivate the soil under infested trees. This will expose overwintering pupae to predators. Remove mulches and replace with new material in the spring.


Pear midge (Contarinia pyrivora)

This pest attacks pear trees only.

Typical symptoms: Small fruitlets become swollen and distorted and they blacken. Such fruit fails to develop normally; when it is cut open, small larvae may be found inside.

Prevention and treatment: Grow early- or late-flowering pear varieties which should not be flowering when the midge is laying its eggs. Pick off all affected fruitlets and collect up all fallen fruit as soon as it is noticed. Destroy immediately. Lightly cultivate the soil around the trees in summer or autumn to expose midge cocoons. Remove and compost mulches in autumn; replace with fresh material in the spring.


Plum fruit moth (Cydia funebrana)

Plum and damson are susceptible to this insect.

Typical symptoms: Small white or pink caterpillars eat into the fruit in mid- to late summer. The fruit rots and/or ripens early.

Prevention and treatment: Collect up and destroy affected fruits as soon as the presence of this pest is noticed, before the caterpillars leave them.


Plum rust (Tranzschelia prunispinosae)

This affects plums, apricots, peaches, almonds and nectarines (also Anemone species).

Typical symptoms: Bright yellow spots appear on the leaves from mid-summer. The leaves turn yellow and may fall early.

Prevention and treatment: Pick up and remove all fallen leaves in the autumn. If they are made into leafmould, do not use this on susceptible trees. Remove anemones in the vicinity if the problem is severe.


Plum sawfly (Hoplocampa flava)

Plum sawfly affects plums and damsons.

Typical symptoms: Creamy-white sawfly larvae eat into developing fruit. Holes in the damaged fruit exude a sticky “frass”. The fruit may fall prematurely, severely reducing the crop. The level of attack may vary considerably from year to year.

Prevention and treatment: Remove and compost all fruit that falls early. Where this pest is known to be a problem, spray with derris as directed on the container, usually when the petals fall.


Poor fruiting

This affects all tree fruit.

Typical symptoms: Various factors can be responsible for poor fruiting, frost being an important cause.

Prevention and treatment: See Plant Disorders – Understanding the Problem


Red spider mite, fruit tree (Panonychus ulmbi)

Apples, pears, plums and damsons are susceptible to this pest.

Typical symptoms: Leaves are speckled, bronzed and dried up; they may fall prematurely. With the aid of a magnifying lens, tiny mites may be seen under the leaves.

Prevention and treatment: Encourage the activities of typh lodrom id mites and anthocorid bugs, the natural enemies of this pest. Where mites are present in small numbers, remove all infested leaves. If the infestation is severe, spray with derris or insecticidal soap—though this can be counter-productive as the sprays can harm natural predators.


Silver leaf (Chondrostereum purpureum)

This affects plums, damsons, cherries, apples, apricots (also hawthorn and other rosaceous trees and shrubs).

Typical symptoms: Silvery sheen appears on the leaves; symptoms may be confined to a single branch initially. Infected wood shows a dark brown discoloration within when cut through and may die back in late summer.

Prevention and treatment: Do not prune susceptible trees between early autumn and late spring; the disease will gain entry through pruning cuts more easily when the tree is not actively growing. Natural recovery is quite common. If the disease persists, cut out and burn or dispose of infected wood. Treat pruning cuts with Trichoderma paste. B I nab Trichoderma pellets can be used to treat infected trees and to protect those at risk.


Wasps, common (Paravespula vulgaris)

Apples, pears, damsons and plums are attacked.

Typical symptoms: Large holes are found in ripening fruit in summer and early autumn.

Prevention and treatment: Tolerate damage if possible; at other times of the year, wasps are useful predators of caterpillars and other pests. Wasps very often extend damage to fruit caused by diseases, disorders or pests such as birds. Dealing with these problems may reduce wasp damage. If essential, trap wasps in jars containing a little jam, some water and detergent.


Winter moths (Operophthera brumata, Alsophila aescularia, Erranis defoliaria)

Apples, pears, plums and damsons are susceptible to winter moths.

Typical symptoms: Young leaves, flowers and buds are eaten by “looper” caterpillars. These tend to drop to the ground when disturbed.

Prevention and treatment: Apply tree grease or grease bands to trees and stakes from mid-autumn to late spring (see Garden Pests and Diseases – Barriers and Traps). These will prevent the female moths from making their way up into the tree. In spring, check trees regular- ly and remove any caterpillars found. If the problem is severe, spray with derris at bud burst.


Woolly aphid (Eriosoma lanigerum)

This affects apple, crab apple and other related ornamental plants.

Typical symptoms: Conspicuous tufts of white “cotton wool” appear on stems and branches of trees. This “wool” is protecting colonies of aphids. Infested stems and branches may develop hard, irregular, woody swellings which can split open, allowing diseases such as canker to infect the tree.

Prevention and treatment: See Aphids as Garden Pests


02. February 2011 by Dave Pinkney
Categories: Fruit & Veg, Organic Gardening, Pests and Diseases | Tags: , , , | Comments Off on Pests and Diseases of Tree Fruit

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