Are your apples rotting on the branch? Do your plums have no stones inside? What are those unsightly orange spots on the leaves of your pear tree? This article will help you identify and deal with common fruit tree diseases.
Apple tree diseases
Fungal diseases are often to blame for problems affecting fruit trees, including apples. Some are more serious than others. Honey fungus, for example, can kill an apple tree outright while sooty moulds may only affect the appearance of fruit.
If you intend to eat the fruit, fungicides are not an option so control tends to be limited to removing any damaged fruit, pruning infected branches and keeping the grounds clean by disposing of leaf litter and dropped fruit.
Brown rot (Monilinia) is one of the easiest fungal diseases to spot as it causes fruit to literally rot on the branch. Brown rot may enter through wounds caused by birds, poor pruning technique or other disease agents. Apple scab (Venturia inaequalis) is one such culprit. This fungal disease leaves circular patches on fruit.
Silver leaf disease is a fungus which affects several types of fruit tree, including apples. As the name suggests, this disease leaves a silvery sheen on some of the leaves. More seriously, silver leaf disease causes branch and shoot dieback. When pruning, you might also notice a dark stain within the branch.
Dieback is a common result of fungal infections. Coral spot (Nectria cinnabarina) is another fungus that can attack apple trees and is recognisable through the tiny pink bumps that form on the dead branches.
A less common cause of shoot dieback is fireblight (Erwinia amylovora). This is a bacterial disease and symptoms include wilted blossoms, a milky discharge at wound sites and red ‘fox fur’ stained branches. Severe infections give the appearance of scorching, hence the name.
Fireblight also affects pear trees but rarely bothers plums. It thrives in warm weather so is more of a threat to trees which blossom in the summer. There are no chemical control measures for fireblight but pruning back to healthy wood can help.
Sunken, misshapen cankers in branches and trunks are often bacterial in origin and affect all kinds of woody plants.
Pear tree diseases
While pear trees often suffer from diseases similar to those that affect apples (e.g. fireblight, pear scab, etc.), there are some specific threats.
Have you noticed bright orange spots on the leaves of your pear trees? This is likely to be evidence of the fungus Gymnosporangium sabinae or pear rust. While the fruit is rarely affected, cankers can form on branches and so these need to be pruned. The pear rust fungus needs junipers to complete its life cycle so removing nearby juniper bushes or trees can help control the issue.
If your pear tree leaves develop black spots late in the season, a different fungus could be to blame. Fabraea leaf spot (Fabraea maculata) can cause your pears to become stunted and misshapen so it is important to remove and destroy fallen leaves and fruit to prevent spread.
Plum tree diseases
Plum trees tend to be more resilient to fruit tree diseases than apples.
Gardeners shouldn’t be too relaxed though as plums are attacked by diseases and some varieties, including Victoria plums are more vulnerable than others.
As with apples and pears, brown rot of plum trees is a problem which needs prompt attention. Never leave rotten plums on the branch and be sure to destroy all infected fruit.
One disease unique to plums is pocket plum (Taphrina pruni). This is another fungal infection which deforms the fruit and destroys the stone, leaving the characteristic empty pocket within.
What about fruit tree pests?
Some fruit trees look diseased but may actually be victims of pest attacks. Various species of moth will burrow into apples, pears and plums, leaving holes on the outside and an unpleasant surprise on the inside.
The apple capsid bug (Plesiocoris rugicollis) leaves holes in leaves and bumpy blemishes on fruit although these are only surface deep.
If you notice fluffy white growths on branches, you could be suffering from an infestation of woolly aphids (Eriosoma lanigerum). A type of blackfly, these pests secrete a waxy liquid which covers them as they feed on sap. Curling, discoloured leaves and stunted fruit can indicate the presence of rosy apple aphids.
Meanwhile, apple sawfly leave a distinctive ribbon-shaped scar on the surface of the fruit.
Similar pests (e.g. plum moths, pear midge, pear slug sawfly) operate on other fruit trees and may need spraying with the appropriate insecticides. Sometimes a soapy wash is enough to deal with minor infestations.
There are many sources of fruit tree diseases and it can take a trained eye to correctly identify the cause of wilting blossoms, rotting fruit and dying branches. Get in touch with Arborcure for a reliable diagnosis and treatment plan.