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Fruit trees should not be missing in any garden, because fruit simply tastes best fresh from the tree or bush. Unfortunately, despite the best care, they can be attacked by various fruit tree diseases. They can be caused by viruses, bacteria and fungi, but can also be transmitted by pests. Therefore, you should keep an eye on the trees all year round. If detected early, fruit tree diseases can often be treated well, in the best case, of course, without chemical agents.

Fruit tree diseases from A - Z

Determine and fight

Determining fruit tree diseases is not easy due to the large number and the sometimes parallel occurrence. While some occur on different fruit trees, others affect only certain types of fruit. Some diseases, such as fire blight, are notifiable. Fruit tree diseases first show up as changes in the leaves, flowers and fruit, but later branches, trunk and roots can also be affected. In order to be able to determine damage patterns, it means comparing, analyzing and checking.

apple scab

Apple scab is one of the diseases that can affect apples and pears. Starting in May, an infestation causes olive-green to brown, irregularly shaped spots on and under the leaves and on the fruit. The spots on the fruit develop into brown cracked areas where fruit rot fungi can colonize. Taste and shelf life suffer.

  • Treat apple trees with preparations containing copper
  • Remove infected leaves
  • In case of severe infestation, use approved fungicides as a last resort
  • Preventively remove the autumn leaves lying on the ground
  • Treat fruit trees early with plant-strengthening horsetail broth

bacterial burn

Bacterial blight mainly affects pome fruit such as plum, pear and cherry trees. It occurs preferably in spring when the buds sprout and in autumn when the leaves are falling, in cool, damp weather. Detected too late, this disease can become a serious problem for the tree.

Affected fruit trees show round, 1-2 mm small leaf spots in early summer. They are light at first, later turn brown and dry up. They have a light green, slightly chlorotic edge. In some cases, flowers, buds and fruits can also be affected and gum discharge can occur. The bark of the trunk and branches shows dark, sunken areas.

  • Cut out affected branches and trunks down to the healthy wood
  • Treat cut wounds with wound sealant
  • Any clippings in the household waste, do not dispose of in the compost
  • Control disease with copper-containing fungicides
  • Spray before the first frost and during leaf fall
  • Spray fruit trees until they are dripping wet
  • Complete recovery of the plant, usually not possible with these means
  • Fungicides primarily have a preventive effect

pear grating

Pear rust is one of the diseases that only affects pear trees. A fungus is also responsible here. An infestation is favored by the proximity of a juniper tree, which the fungus uses to hibernate before moving back to the pear tree in early spring. The trees do not necessarily have to be right next to each other, because winds can carry the fungal spores more than 500 m. Clear symptoms of an infestation are irregular, orange-red spots on the leaves from around May/June. The fungus leaves wart-like thickenings on the underside of the leaves, in which the spores mature.

  • Spread can be stopped with early application
  • Remove diseased parts of a nearby juniper
  • If the juniper is heavily infested, remove it completely
  • This alone cannot eliminate infestation on the fruit tree
  • Spores can also fly over greater distances
  • Spraying for prevention and control with a suitable fungicide
  • Spray preventively at the beginning of sprouting

leaf fall disease

Jostaberries, gooseberries and currant bushes can be affected by leaf fall disease. The harmful fungus responsible overwinters on the leaves lying on the ground. In the spring, the spores are then carried by the wind to the freshly sprouted leaves and the shrub becomes infected. Plants lose most of their leaves prematurely.

Symptoms of an infestation are brownish to black leaf spots of different sizes, initially on the undersides of the leaves. The spots become larger and merge into one another until the entire leaf is affected. They fall off and growth stops. Direct combat is not possible. However, fallen leaves should be removed and care should be taken to ensure that the plant population is not too dense, so that the leaves can always dry off quickly.

tip: This fruit tree disease can be prevented by paying attention to optimal cultivation conditions and care in advance and by preferring varieties with a low susceptibility.

powdery mildew

Powdery mildew is a fair-weather fungus because it occurs when the weather is particularly fine, i.e. warm and dry, with temperatures above 20 °C. The fungus appears around July and overwinters on living parts of the plant. All green parts of the plant are affected. Apples, pears, table grapes and gooseberries can show symptoms of an infestation.

In the event of an infestation, the fungus covers shoots, leaves and fruits with a whitish, washable coating. After several consecutive hot days and cool nights with heavy dew formation, the infestation is particularly severe. Affected plants grow more slowly. However, it is rare for the entire plant to die off.

  • Remove affected plant parts
  • Regular sprays with herbal broths
  • Alternatively, combat powdery mildew with suitable antifungal agents
  • Prevention is the best protection against powdery mildew
  • Therefore, pay attention to well-ventilated locations
  • Leaves should be able to dry off quickly
  • Mushrooms need moisture to develop
  • Even morning dew can be enough
  • Accordingly, thin out fruit trees regularly
  • Pay attention to a balanced nutrient supply
  • Prefer hardy varieties

fire blight

Fire blight is caused by a bacterium and affects fruit trees such as apple, pear, quince and other pome fruit. It can spread very quickly and is initially reflected in dried-looking flowers, fruits and young shoots. Affected parts later turn dark brown to black, they look as if they have been burned. When the humidity is high, a sticky bacterial slime can appear on the affected parts of the plant.

  • Diseases such as fire blight are notifiable
  • Immediately notify the responsible plant protection office
  • There is no effective way to combat it
  • Remove all affected plant parts
  • Cut at least 30 cm into the healthy wood
  • Remove clippings completely
  • Do not dispose of in the compost
  • It is best to collect them in plastic bags and burn them later
  • Thoroughly clean and disinfect the cutting tools used
Fire blight on the pear tree

tip: In order to counteract an outbreak of this disease, it is advisable to look for particularly resistant varieties when buying fruit trees.

frizz disease

Diseases such as curling disease are comparatively easy to diagnose. She becomes through a sac fungus and occurs on peaches, cherries, nectarines and apricots. The fungus lives from June to February in dead, decomposing plant material, on shoots and bud scales, on which it feeds and in which it also overwinters.

The leaves of affected fruit trees are thickened and blistered. They turn yellowish to reddish, curl up, then dry up and fall off. There is a velvety covering on the top of the leaves. However, fruits are rarely attacked. With a heavy infestation, gum flow can occur, causing entire shoots to die off.

  • Fight frizz as early as possible
  • The risk of infection increases at temperatures above 10 °C
  • Gather and dispose of the leaves underneath
  • Prune affected shoots back to healthy wood
  • Fertilize the plant to strengthen it
  • Combat fungus directly using a broad spectrum fungicide
  • Preventive plant strengtheners bring good results
  • Continue treatment consistently until budding
Curl disease on the peach tree

tip: The spores of Taphrina deformans get between the newly sprouted young leaves in spring due to wind or rain, which can only be infected now. In order to counteract this, you should therefore ensure a sunny and, above all, airy location when planting.

toad skin disease

  • Toad disease caused by wound parasites
  • Penetrate through open wounds in the trees
  • The disease affects sweet cherries, peaches, apricots and plums
  • Occurs mainly after frost damage
  • Symptoms are elongated, dead parts on the branches
  • Affected parts of the bark have bulging spots
  • These stand out from healthy tissue
  • The pustular fruit bodies sit on the tumors
If the bulges tear open, rubber flow occurs

Combat is limited to prevention. It's all about the right location. Because the tree should be protected from frost and waterlogging. Heavily affected branches can be completely removed and areas affected by necrosis can be cut out down to the healthy tissue.

Monilia fruit rot

Monilia fruit rot affects pome and stone fruit such as apples, pears, plums and cherries, both ripe and unripe fruit, and the fruit tree itself. This disease is spread by wasps during fruit ripening. Initially, small rotten spots appear on the fruit. They turn brown on the inside and outside and have circular, white-greyish spore beds. Later, affected fruits fall off or dry up on the tree. One then speaks of fruit mummies.
Since the fungus overwinters in the fruit, it is important to completely collect and destroy any infested fruit that is still on the tree or that has already fallen. If you leave the fruit mummies on the tree, they can infect healthy fruit next year.

Monilia peak drought

Apple, pear, plum, apricot, peach, sweet and sour cherry trees can be affected by the Monilia peak drought. In the spring, the causative fungus penetrates the shoots via the blossom and damages them so severely that parts of the plant die off. The fruits, which later hang on the tree as fruit mummies, are also affected. Since the fungus overwinters in the tips of the shoots, infected shoots should be cut back into the healthy wood immediately after flowering.

Monilia peak drought on apple tree

fruit tree cancer

Fruit tree cancer is also triggered by fungi that penetrate the plant through cuts and cracks. Apple and pear trees in regions with high rainfall are at risk. The first signs of infestation are small, brown-red spots. Cancerous growths form on older branches or the trunk and continue to spread. Above these growths, shoots and branches die off.

  • Prune affected trees back to healthy wood
  • Treat larger cuts with wound sealant
  • Dispose of clippings in the residual waste or incinerate
  • Cut off young shoots about a hand’s breadth below the growths
  • Supplementary spraying with copper-based fungicides
  • Preventively avert injuries to the trees as far as possible
  • Avoid locations that are too wet and varieties with increased susceptibility
Fruit tree canker on an apple tree

red pustular disease

Host plants of red pustule disease include pome and stone fruit. The pathogen primarily attacks dead plant parts and penetrates healthy tissue through open wounds. If the water content in the wood then decreases, the fungus can spread quickly. Yellow to pale red spore beds can be seen on the bark. Infested wood should therefore be cut out after the vegetation period and attention should be paid to a balanced supply of water and nutrients.

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