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The apricot is one of the most popular fruit trees in your own garden. The fruits of Prunus armeniaca are harvested for their sweet aroma and numerous processing options. Despite its popularity, the apricot tree is one of the plants with a high sensitivity to diseases, which makes cultivation difficult. There are a number of diseases that can severely affect trees. Vitality and fruit yield of the specimens are negatively affected, which makes appropriate countermeasures necessary.

Diseases of the apricot tree

Demanding and sensitive. The apricot tree is one of the "mimosa" among fruit trees and proves to be one of the most difficult species for many gardeners to cultivate. Prunus armeniaca is not only dependent on a warm, wind and rain-protected location with full sun, but also nutrient-rich soil that must not be too damp. Due to its dependence on optimal locations, the apricot is one of the types of fruit that are difficult to grow in many regions. Since the risk of illness is very high, you need to know the symptoms and causes of the 10 typical apricot diseases. Only then is it possible to use a suitable solution.

Tip: Compared to the numerous diseases, the apricot is naturally only slightly susceptible to pests. The only characteristic pest is the apple tree glass wing moth (Synanthedon myopaeformis), whose damage only occurs after a heavy infestation by butterflies.

Monilinia

Monilinia fructigena. Source: H. Krisp, Monilinia fruit rot, crop from Plantopedia, CC BY 3.0

Monilinia disease is one of the biggest threats to the apricot tree. This is caused by the following two types of fungi, which attack different parts of the trees:

  • Monilinia laxa (spike drought): shoot tips, flowers, leaves
  • Monilinia fructigena (fruit rot): fruits

Both pose a major threat as they can easily spread via their spores and infest even healthy trees. For this reason, it is important to protect the apricot tree from these, since Monilinia cannot be combated directly, only prevented. The following symptoms indicate peak drought and fruit rot:

  • Spots of rot appear on fruits
  • brown and circular
  • Spread over the entire fruit
  • Spore deposits in a yellow-grey color develop
  • arranged in a ring
  • fruit drop occurs
  • fruit mummies are formed
  • Foliage and flowers suddenly wither in spring
  • Shoot and branch tips dry out
  • turn grey
  • dried flowers and leaves are left hanging
  • Gum flow occurs in wet weather

Since the affected parts of the plant remain on the tree in most cases, the fungi spread even further. So the cause must be tackled directly to protect other nearby trees from the disease. As soon as you discover the above symptoms, do the following:

  • collect fallen leaves
  • also the fruits
  • Remove affected leaves, fruits and flowers
  • Cut shoots back into healthy wood
  • Use plant strengthener after sprouting

It is very important to properly dispose of the removed and collected plant parts. You must not put these on the compost, otherwise the fungal spores can spread further. This is the only solution against Monilinia, which can take a toll on your apricot tree and is more common in humid areas.

shotgun disease

CoolKoon, Peach shot hole disease, crop from Plantopedia, CC BY-SA 4.0

You have to contend with shotgun disease if your apricot tree has to endure a damp location or a rainy spring. The Wilsonomyces carpophilus fungi make themselves comfortable in such weather and are clearly recognizable by the following symptoms when infested:

  • young leaves get leaf spots
  • Leaf spots are round
  • turn red-brown
  • Leaf spots turn into holes over time
  • reminiscent of shot holes
  • early leaf fall
  • fruits are attacked
  • Fruit spots are round and sunken
  • red border of the fruit spots
  • go in and fall off
  • Gum flow follows

As with Monilinia, all infected parts of the plant should be removed immediately and preferably disposed of in bags. The spores are extremely persistent. As a preventive measure, you should definitely collect autumn leaves and carry out maintenance or thinning cuts every year. During the infestation, preparations with the following ingredients can be used:

  • net sulfur
  • copper
  • clay

In the worst case, you have to resort to fungicides.

Sharka disease

anonymous, Plum pox in apricot, crop from Plantopedia, CC0 1.0

Sharka disease is one of the notifiable diseases on the apricot tree. This is triggered nationwide by the Sharka virus, which is transmitted by the following aphid species:

  • Green peach aphid
  • Large plum aphid
  • Green plum aphid
  • hop aphid

Due to the rapid spread and the fact that the virus cannot be combated, the prospect of an infestation does not look good. You can only fight the aphids, but in an emergency you have to clear and burn your apricot tree. Virus-free rootstocks or resistant varieties should also be used. There is no better solution in this case. The virus can be recognized by the following symptoms, which appear from July:

  • Visible brightening on leaves
  • annular or cloud-shaped
  • fruits scar
  • Pocky and striated deformities appear
  • Vitality of the trees deteriorates drastically
  • fruit inedible
  • reddish colored flesh
  • Flesh takes on the consistency of gum

Valsa bark disease

Curtis Swift, Peach Cytospora Canker 012, crop from Plantopedia, CC0 1.0

Infection with the dangerous Valsa bark disease occurs in autumn or winter when the fungus Leucostoma personii gets into the apricot wood via one of the following wounds:

  • frost cracks
  • hail injuries
  • lacerations

Above all, unclean cutting measures over autumn and winter lead to infection. For this reason, pruning measures should take place at other times of the year. Above all, apricot trees with poor vitality are affected by this disease, which can worsen in winter. The symptoms are:

  • withered leaves
  • turn brown
  • Shoots and branches dry up
  • can affect the entire tree
  • tree can die
  • Gum flow occurs
  • sinking bark
  • black fruiting bodies with warts form
  • fruits rot
  • Sores brown with pustules tawny or gray in colour

If regular cutting measures and an effective wound closure are used, an illness is only slightly possible. Preparations based on copper just before the leaf fall or after it has a preventive effect.

Spray spot disease

Jerzy Opioła, Blumeriella jaapii a2 (2), crop from Plantopedia, CC BY-SA 4.0

If spray spot disease occurs, you cannot fight it. The Blumeriella jaapii fungi are the cause of the following diseases in years with high humidity from June:

  • Upper side of leaf red-brown dotted
  • white coating on the underside of the leaf
  • Loss of leaves until the tree is bare
  • premature fruit drop occurs more rarely

Since removing the foliage will not control the fungi, you will need to use fungicides as a solution. For prevention, collect and burn the fall leaves before winter. This way the fungus cannot spread.

frizz disease

Peach curl disease

The curling disease can be recognized by leaves that curl up more and more and then get spots in a light green or red color. Over time, they turn pure white and take on a gummy consistency until they fall off completely. This is caused by sac fungi, which attack particularly weak and old apricots after wet and humid winters. Remove the affected parts of the plant and dispose of them in the household waste. When planting your specimens, pay attention to the location to avoid curling disease. Fungicides offered for control have only a minor effect on the fungi and therefore do not have to be used.

bacterial burn

Jerzy Opioła, Pseudomonas syringae a2 (3), crop from Plantopedia, CC BY-SA 4.0

Another disease on the apricot tree that cannot be combated directly is bacterial blight. Prunus armeniaca bacterial blight is caused by the fungus Pseudomonas syringae pv.morsprunorum, which occurs in autumn. Symptoms are very similar to shotgun disease with a few exceptions:

  • gum flow
  • Sheet margins spotted
  • Spots brown and round
  • fruits blotchy
  • spots black
  • Shoots die
  • Necrosis of the bark occurs

The best solution to combating apricot tree disease is prevention. Be careful not to leave any major cuts. Annual thinning is recommended. The trunk can be whitened and the trees sprayed with copper preparations.

Black sooty mold

Sooty mold on Schefflera. Source: Amnon Shavit, Sooty mold Schefflera 1, crop from Plantopedia, CC BY-SA 3.0

The black sooty mold does not pose a major threat to the apricot tree, since only the affected leaves have to be removed. The black spots, which can discolour the entire leaf, are caused by aphids. More specifically, through the excretions that contain sugar. Harmful fungi grow on these, which affect the foliage. The best solution is to use home remedies to control aphids.

Verticillium wilt

Howard F. Schwartz, Verticillium wilt dahliae, crop from Plantopedia, CC BY 3.0

Verticillium wilt is difficult to combat because the fungus of the same name survives in the soil for up to 15 years. From there, they prevent the roots from absorbing moisture, which has a negative effect on the water absorption of the Prunus armeniaca. Even if you water enough or it rains a lot, the trees just don't get enough water. The following damage is to be mentioned:

  • withering leaves
  • premature leaf fall
  • Shoots and whole branches partially die off

Since the mushrooms cannot be removed from the soil, you need to remove the fall foliage to stop the spores from spreading further. Likewise, all affected shoots and branches are cut back into healthy wood. That's all you can do here. Usually the wilt does not appear if it is a good location.

powdery mildew

Powdery mildew on maple leaf. Source: Jerzy Opioła, Powdery Mildew Acer DK43 (1), crop from Plantopedia, CC BY-SA 4.0

Powdery mildew is a bigger problem with apricots than many gardeners realize. The typical fungal disease occurs quite frequently and can be combated by various measures. In the case of powdery mildew, it is important to know why this Prunus armeniaca infests at all. The causes for this are:

  • missed cuts
  • nitrogen-rich fertilization
  • compacted soils

It may also be the case that you have planted a sensitive variety. In this case, you have to reckon with the fact that sooner or later there will be an infestation of powdery mildew. The disease can be recognized by the white coating that appears floury and spreads to the leaves, fruits, blossoms and young shoots of the apricot tree. The following measures are effective against the fungus:

  • remove affected plant parts
  • clear crown
  • injecting non-containing preparations

Powdery mildew is easy and quick to treat if you follow these steps. You can also prevent an infestation if you thin out the crown every year so that it gets enough air and is therefore not a basis for fungal growth.

Notice: Many of the diseases mentioned can be prevented or mitigated by an ideal location and appropriate care. Apricots are among the trees that require a significantly warmer space than other fruit trees, making cultivation easier in wine-growing areas and regions with mild winters.

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