Common leaf diseases on fruit trees

Fruit trees can be attacked by a wide variety of diseases. Pure leaf diseases are fortunately not that many, but numerous diseases can be determined well on the leaves. The most dangerous fruit tree diseases are fire blight and sharka, followed by fruit tree cancer.

Fire blight

Many leaf diseases are caused by fungi, the fire blight pathogen, on the other hand, is a bacterium (Erwinia amylovora). It is not a pure leaf disease, but it is best recognized by the leaves. Affected fruit trees are mainly pome fruits, i.e. apples, pears, quince and others. There are several possibilities of infection and spread, for example migratory birds, the weather situation, contaminated plant material, insects, animals and also by humans. The most common type of infection is the flower infection, followed by the shoot infection and older infected areas that have become active again. Fire blight can be recognized by the fact that the leaves of some shoots are black-brown and have dried up. The bacterium clogs the pathways.

The leaves can no longer be supplied with water, they die.

• bacterium
• Not a pure leaf disease, but can be recognized by the leaves
• Infection possible from spring to autumn
• Ideal growth temperatures between 21 and 28 ° C
• The flowers are particularly at risk
• Entry portals, peduncle, respiratory openings, wounds
• Distribution depends on tree health and age
• Bacteria survive in the diseased bark (sunken bark plates)

Attention: mandatory registration

The fire blight is notifiable. It's a quarantine disease. Any suspicious symptoms must be reported to the plant protection office. If it is proven to be a fire blight, control measures are prescribed. Not only pome fruit trees are attacked, but also other popular woody plants such as mountain ash, rock pear, ornamental apple, medlar, medlar, hawthorn, firethorn, hawthorn and others. Fire blight can only be combated in older trees. Young fruit trees should be cleared. In the case of heavy infestation, clearing is also the best option. When choosing a variety, it is important to choose a robust type of fruit. However, there is no resistance.

• Cut diseased shoots back into healthy wood
• Report infestation (plant protection office)
• Accumulated wood must not be composted
• It is best to burn it
• Disinfect cutting tools (with 70% alcohol)
• Plant robust fruits

Sharka

Sharka disease is caused by a virus and affects stone fruits, mainly plums, plums, peaches, nectarines and apricots. This disease is also notifiable. Due to different virus strains, the symptoms on the plants can also differ or they are differently pronounced. You can see light olive-green rings that can develop into black dots (dead tissue) on the leaves. These mainly form in spring, around May / June. The fruits, on the other hand, have depressions that are pox-like or linear. Below that, the pulp takes on a reddish color and it takes on a rubbery consistency. Often the fruits fall off prematurely.

• Viral disease
• Attacks stone fruit
• Prefers some types of fruit
• Can be recognized by the light olive colored rings on the leaves, mainly in spring
• Later black spots (dead tissue)
• Fruits also affected
• Particularly intense occurrence in warm and dry conditions during the growing season
• Transmitted by aphids or by grafting with infected pods or rootstocks

You cannot fight the virus directly. However, the spread should be avoided or at least reduced. This can be done through some targeted measures. Even prevention is not

possible.

• Fight aphids
• Clearing and removing infected plants
• Use virus-free vines and rootstocks
• Plant varieties and rootstocks that are less susceptible to the virus or resistant

Apple scab

Apple scab is one of the most important apple tree diseases worldwide. The culprit is the hose fungus, Venturia inaequalis. Typical are dull olive green spots on the leaves, which later take on a brownish to blackish color and can flow together. They form necrosis, which in turn leads to premature leaf fall. The disease can also be recognized by the fruits. They usually have darker colored spots. Star-shaped cracks can appear in these. Other pathogens enter the damaged apple through the cracks. This affects the shelf life, but has no effect on the consumption.

• Fungal disease
• Affects leaves and fruits
• In addition to apples, pears, cherries, peaches and other types of fruit are also affected by rust
• High rate of reproduction
• Infection depends on the weather, moisture and temperatures between 16 and 22 ° C are ideal

Prevention is better than cure

The selection of robust fruit tree varieties is important, as is the correct location and good care. Resistant varieties are now on the market and should be given preference. Furthermore, the following things must be observed:

• Dispose of infected leaves and fruits. Do not leave it lying around and do not put it on the compost
• Thinning trees regularly so that the leaves can dry well (wind)
• Balanced fertilization
• Preventive spraying with appropriate means (always only before precipitation)
• First spray before the spore flight in March

The control includes spraying at the beginning or shortly before the spore flight at the end of March. A combination of preventive coating and contact spraying is beneficial. The same means are not permitted for home gardens as for commercial cultivation. In addition, some are constantly being removed from the offer or new ones are added. Here you should get the relevant information from a specialist.

• Injections for prevention
• Surface spraying - all infected parts of the tree are protected by a closed surface
• It is important to adhere to the concentration and the recommendations for use.
• Usually at least 5 injections are necessary, with an interval of 7 to 14 days

Apple powdery mildew

Apple powdery mildew is powdery mildew and is caused by the fungus Podospharea leucotricha. Leaves, but also other parts of the plant, are covered with a whitish, floury layer, which explains the name apple powdery mildew. The pathogen lives on the surface of infested plants, but penetrates them to remove water and nutrients. Infections are only possible in young tissue.

• Fungal infection
• Only attacks apple trees, fungus has specialized
• Whitish-floury coating on infected parts
• Only young tissue is infected.

In addition to leaves, flowers, shoots and fruits can also be infected

• Infested flowers do not produce fruit
• Usually occurs between mid-May to mid-June.
• Preferably dry weather and temperatures between 20 and 25 ° C
• Affected leaves dry up and fall off. Annual shoots bald from below. Apples show a reticulate russeting.

Again, all sorts of things can be achieved through prevention. Infected shoots should be removed in good time, right at the time of winter pruning. Here, too, it is important to have a clear crown, which is why it should be lighted regularly. In addition, the susceptibility depends on the variety. Some varieties are highly susceptible, for example Jonagold, Elstar and

Cox orange. As a rule, apple varieties with hairy leaves are more susceptible than those with bare leaves.

• Thin out regularly
• Remove infected shoots
• Select apple varieties with smooth leaves
• No varieties with hairy leaves

The infestation can be prevented or avoided by a combination of different measures. be contained. These include the cutting measures and spraying.

• Winter pruning - remove infected shoots
• Regular breakout of infected shoot tips in early summer
• Sulfur spray on susceptible varieties
• Start after flowering until August

Pear grid

Pear rust is a fungal disease, more precisely a rust fungus. This fungus actually attacks a wide variety of juniper species. There it causes knotty thickening of the branches. In spring, the spores are distributed by the wind and get onto the leaves of the pear trees. This infection thus begins on the upper side of the leaf. Initially, orange-red spots can be seen on the leaves. These are increasing continuously. If the weather is right, the fungus can multiply explosively. Insects help with this. They are attracted by excreted nectar. In summer the fungus grows through the leaf. Irregular, brownish growths and spore beds now appear on the underside of the leaf. When the spores are ripe, the surface bursts, the winter spores fly out and can now infect the juniper again.

• Young trees can be seriously damaged

Growth and harvest are severely impaired

• Settles on juniper
• Two junipers in particular are affected: Sead tree (Juniperus sabina), Chinese juniper (Juniperus chinensis)
• Fungal disease
• Spores infect pear trees
• Orange-red spots on the upper side of the leaf
• Later irregular, brownish growths (spore beds) on the underside
• When the spores are ripe, the spores fly off

To prevent infestation, you can only remove all junipers from the garden. However, if the neighbors also have some, you have to convince them too. It is safer to use plant strengtheners such as horsetail extract. The trees should be sprayed every 14 days, starting with the shoot, at least 4x.

• Remove juniper
• Plant resistant species z. B. Juniperus communis, common juniper.

The control must start with the pear tree and the juniper, otherwise the cycle will not end. The winter spore deposits on the juniper must be combated. It is best to remove the affected trees and bushes. The flight radius of the spurs is around 500 meters, and more in strong winds. At this distance, the trees should be removed. Usually this limit goes beyond your own garden and the removal becomes difficult. The owners often do not see this. Sometimes, however, it is enough to remove the affected areas from the trees. Alternatively, plant resistant species can be used.

• Control of junipers: cut out the affected areas or, even better, remove the entire plant, alternatively plant a resistant variety
• Control of the pear tree: spray fungicides, preferably in the spore flight phase (Duaxo Universal mushroom-free from Compo). The agent is also effective against other fungi, e.g. B. Curl disease, rust, scab, powdery mildew and many types of leaf spot diseases. Use plant strengthening agents, prophylactically inject triazole, every 14 days

Sooty mildew

Sooty mildew is a black fungus infestation. It mainly occurs in late summer. The soot fungi prefer to colonize leaves on which honeydew sticks. These in turn are the excretions of aphids and scale insects, whiteflies and cicadas. Apple trees, pear trees, apricots, cherry trees, peach trees, plums and plums are affected. The infestation can be recognized by black-coated spots of different sizes on the upper side of the leaf. The leaves can also be colored completely black. They can no longer absorb solar energy and die. In the case of fruit trees, the damage is usually not very severe. Ants harvest the sticky secretions.

• Fungal disease - soot fungus
• Settles on excrement of harmful insects
• Many fruit trees affected
• Usually no major damage

There is not much that can be done about prevention. Strengthening the trees is a great option. Plant strengtheners help with this. In addition, the trees must be checked regularly for pests so that they can be combated as early as possible. If there is no honeydew, there is also no soot infestation.

• Plant strengtheners
• Control pest infestation

The control is mainly directed against the pests. Aphids in particular need to be controlled. In addition, ants are to be kept away from the woods. They promote the secretion of honeydew because they want to harvest. They keep the aphids like pets.

• Control pests, especially aphids
• Keep ants away

Shotgun Sickness

Shotgun disease can affect apricots, cherry trees, peach trees, plums, and plums. The cause is a fungus, more precisely Wilsonomyces carpophilus. The disease can be seen on the new leaves. There are red-brown, round spots that later become holes. If the infestation is more severe, the foliage looks like it has been shot to pieces, hence the name of the disease. The infected leaves dry up and fall off prematurely, usually as early as June or July. The lower parts of the tree are often more infested than the upper ones. The trees can be completely bare early on. The fungus can also attack branches. Young shoots show cracks. Fruits are also affected. They show red-bordered spots and funnel-shaped indentations. Every now and then they are completely crippled. Whole branches can die off. The trees are particularly endangered from May and then

until the end of the growing season.

• Fungal disease
• Mainly occurs in damp, cool, rainy weather
• Multiplies explosively under favorable conditions
• Areas with heavy fog are particularly at risk
• Spread by raindrops
• Fungus penetrates the epidermis and tissues
• Can also penetrate through the attachment points of fallen leaves

In order to combat the shotgun disease, infested leaves must be removed. This also applies to infected fruits. Heavily infested trees must be cut back down to the healthy wood (wood can also be infected). This lowers the pressure of infestation and the leaves on sparse trees dry off faster. In the case of peach trees, copper preparations should be sprayed immediately before the leaves fall. This prevents late infections. Alternatively, synthetic fungicides can be sprayed in summer.

• Remove leaves and infested fruits
• Cut back heavily
• Inject at peaches to prevent late infection.
• Fertilize cautiously, especially nitrogen
• Organic farmers use alumina preparations and network sulfur

Frizziness

The curl disease is also known as vesicle disease. It is triggered by a fungus and mainly affects peach, nectarine, apricot and almond trees. The disease can be recognized by the leaves, which are clearly curled and have light green and / or red blisters when they shoot in spring. The diseased leaves turn whitish-green in color and appear rubbery and brittle in the final stage. The tree sheds the leaves, but produces healthy new shoots. The good thing is that the fungus is not infectious above 16 ° C. However, the tree as a whole is weakened and if the disease occurs for several years in a row, entire branches can die and in the end the tree has to be cleared.

• The pathogen is a hose fungus
• From the end of February / beginning of March, sprout cells are washed into the newly opened buds of the tree by rain. There the not yet unfolded leaves are infected and flower buds are overgrown. From this point on, there are no more antidotes.
• In May the fungus forms spore beds. Recognizable as a soft, plush fluff.
• Infestation occurs particularly in damp winters

The best way to prevent this is to plant disease-resistant varieties, if there are any. It also helps enormously to plant the trees on the wall of a house or, even better, under a roof overhang to protect them from rain in the critical winter months. This is the only way to prevent the infection. If necessary, a tarpaulin can be hung over, at least until the temperature rises above 16 ° C.

• Plant disease-resistant varieties
• Plant trees close to the house or under a roof overhang
• Protect with a tarpaulin if necessary
• Glue rings on the trunk
• Adequate watering
• Sufficient nitrogen fertilization
• Plant strengtheners

Combating is difficult. There are sprays in commercial cultivation, but these are not permitted for the home garden. Since new funds are approved every year, it is worthwhile to ask the specialist trade once.

• Spray with fungicides, usually copper-based agents or peracetic acid, shortly before the buds burst in January or February
• Start at temperatures above 10 ° C

Leaf tan

Leaf tan is a fungal disease that affects leaves and young shoots. Mainly affected are sweet cherry trees and quinces, but also apricots, and sometimes apples and pears. The leaves of the cherry trees turn brown at the end of May, but do not fall off. The entire crown will turn brown by the end of August. The leaves stay hanging even in winter, but they stay curled up. The twisted petioles are also clearly visible. In the quince, chlorotic, light yellow discoloration of the leaves can be seen. The leaves may fall off. The fruits are also affected and are not suitable for consumption.

• With cherries - leaves turn brown, curl up and stick, even all winter long
• With quinces - light yellow discoloration of the leaves, is often due to limescale deposits on the soil

Plant strengtheners such as horsetail broth are used for prevention. When the shoot begins, the spray should be repeated. In the event of an infestation in the months of May to June, copper should be sprayed twice, although this is not permitted for home gardens.

• Plant tonics such as horsetail broth
• Splash copper agent
• Give fruit trees a lot of space, they should stand freely
• Distance to buildings or other trees 6 to 12 m
• Thinning the crown annually

To combat leaf tanning, all leaves should be collected and destroyed. They don't belong on the compost. If copper agents are allowed, inject before buds emerge. Always keep the crown in a nice light and cut regularly.
Conclusion
There are a lot of leaf diseases on fruit trees. Not all are pure leaf diseases; fruits, flowers and shoots can also be affected. In the case of some diseases, however, the leaves indicate the infestation and can be easily identified. There are serious diseases that can end with the death of the tree and there are also more harmless ones. In any case, prevention is better than cure. It is important to choose robust types of fruit. The location and maintenance must also be right. Nevertheless, diseases cannot always be reliably prevented. Early detection and rapid initiation of countermeasures then help. Plant strengtheners help the woody plants and cannot cause any damage.