Not so long ago, the cherry tree, both sweet and sour cherries, was considered very pest-resistant. However, special cultivations, environmental factors and unfavorable locations make the fruit tree susceptible to leaf diseases. One of the symptoms is the curling of the cherry tree leaves. There can be various reasons for this. The following guide gives an overview of the most common causes, presents helpful measures and also gives tips on prevention.
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The black cherry louse
Because of its appearance, the black cherry aphid is often mistaken for a beetle. It is a pest with a spherical, shiny black body with a length of around 2mm. Although there are two types, the black sweet cherry louse and the black sour cherry louse, both varieties are grouped together under the name of the cherry louse because their pest appearance is almost identical. However, the sweet cherry louse causes much more drastic symptoms than its relative. While the cherry tree leaves ripple when it is infested, the black sour cherry louse primarily inhibits the growth of the tree. The leaves simply bulge.
Both species overwinter on the cherry tree leaves. At the end of April or beginning of May, just before the fruit tree sprouts, their larvae hatch and begin to suck in the leaves. However, the black cherry louse only lingers on the fruit tree until mid-May. In the summer months it is often found in nearby grasses. Likewise, the black cherry louse, which leaves the cherry a little later. But if the gardener thinks he has got rid of the pest, he will be happy too soon. In late summer the animals return, mate and the cycle begins all over again.
- the cherry tree leaves curl strongly at the shoot tips
- sometimes the leaves die shortly afterwards
- Honey or soot dew forms from the lice’s droppings, which sometimes contaminate the cherries
- the aphids collect on the underside of the leaves or on the petioles
The most natural way to fight the black cherry louse is with predators such as ladybirds or the larvae of the hover fly. Chemical pesticides tend to be the second choice, not only because of their environmental impact. In order to be effective, those fungicides have to be applied before the cherry tree leaves curl. This requires early detection of the causes. In addition, the pesticides approved in Germany such as pirimicarb, thiacloprid and acetamiprid are only allowed if the louse is present at a minimum. This is two to five colonies distributed over 100 shoots.
The black cherry wasp
Occasionally the black cherry sawfly is harmless, but a strong infestation causes severe damage to the cherry tree leaves. The pest, which affects other fruit plants in addition to cherries, multiplies twice a year. The insidious thing about its mode of reproduction is the pathogenic species that does not require a male. The second generation causes significantly more damage.
At first, the larvae are more reminiscent of snails with their bodies surrounded by a black layer of mucus. With increasing age this mucus disappears, the larva reaches a size of about 10 cm. The adult wasp is significantly smaller at 4-5 mm. Their wingspan is 11 mm.
- the cherry tree leaves curl up and dry up
- window corrosion occurs
- What remains are the subcutaneous tissue and veins of the cherry tree leaves
- eggs on the underside of the leaf in June
Since the control of the first generation took place at the time of the cherry harvest, measures at this time are rather rare. The use of pesticides would result in reduced yields. In order to avoid greater damage, however, fighting the second, more aggressive generation is inevitable. It is similar to the treatment recommendations for the above-mentioned black cherry aphid and is virtually unnecessary if it is infected at the same time. Most often the approved fungicides pirimicarb, thiacloprid and acetamiprid remedy the causes.
The fool’s disease / pocket sickness
The fool’s / pocket disease is a fungal infection that mainly affects plum or plum trees, but also occurs in bird cherry. Taphrina pruni is what the botanist calls the culprit that causes a high harvest loss. On the face of it, it makes the fruits of the fruit trees inedible, but also changes the shape of the leaves. This damage pattern is probably decisive for the somewhat surprising name of the fungal infestation. Visually, the cherry tree looks a little crazy. Unfortunately, the symptoms do not appear until it is already too late to prevent a complete infection of the cherry tree leaves. Rainy days and cold and damp temperatures should make the gardener aware. These climatic conditions offer the fungus the best conditions for spreading.
- pod-shaped fruits
- Fruit ripens prematurely
- the formation of a fruit stone does not occur
- the fruits lack the sweet taste
- they rot early and fall to the ground
- Shoots and leaves show curvatures and thickenings
- A floury coating forms on the fruits
In contrast to the causes of pest infestation mentioned above, no chemical agent is permitted for these leaf diseases. Although the fool’s pocket disease destroys the entire fruit harvest, it does not pose a serious threat to the environment. The treatment of fungicides, however, polluted the surrounding nature. For this reason, the gardener has to resort to alternative methods. Depending on the intensity of the causes, vigorous pruning, thinning of the crown, removal of the infected shoots or just the disposal of the rotten fruits are recommended.
To prevent leaf diseases in the first place, preventive measures should be taken on a regular basis. On the one hand, it is advisable to look for a resistant variety when buying a cherry tree. Furthermore, as much chemicals as possible should be avoided in the care and alternative biological measures should be used instead. Artificial fertilizers often do more harm than good to the fruit tree. For example, it weakens the defense of the tree. A compost layer made of organic material is usually sufficient to provide the cherry tree leaves with all the important nutrients. Even your own fallen leaves can serve as such a compost layer. Sprayings made from self-made plant broths help against pests. As ingredients come here like home remedies
- or horseradish
proven. If leaf diseases are suspected, the affected shoots should be carefully removed.
If the cherry tree leaves curl, it is often due to leaf diseases that are caused either by a fungal infection or a pest infestation. In addition to the curvature of the cherry tree leaves, other symptoms, such as the appearance of the fruit, help to determine the exact cause. Biological treatment methods are always preferable to chemical measures.