Pear trees are delicate. If something is wrong with their living conditions, diseases and pests spread. Some of them leave black spots on the pear, both on the leaf and on the fruit. Nobody wants to put up with that for long.
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Possible causes of black spots
If the leaves or fruits of pears are covered with black spots, several diseases or pests can be the cause. A close look is required to find the cause. This is the only way to take adequate measures and thus solve the problem. You might be dealing with this:
- codling moth
- Pear Blossom Burn
- pear midge
- pear scab
- fire blight
- black spot disease
The apple is not the only fruit that feeds the larvae of this butterfly species. The about one centimeter small and inconspicuous gray colored pests are just as happy to attack pears. In May and June, preferably on warm, humid days, the moths fly around and lay their eggs on leaves and fruit. After hatching, the larvae drill into the pears. The small holes are dark in color and look like black spots from a distance. This impression is reinforced when the larvae have also left their piles of excrement. You can fight or prevent the codling moth and its larvae with one of the following means:
- Predators: earwigs, bugs, parasitic wasps
- Granulose virus (affects only codling moth)
Pear Blossom Burn
Pear blossom smut is a bacterial disease that not only shows up on the blossom, but later also on the leaf and fruit in the form of black spots. The pears marked in this way do not continue to ripen, but instead fall off, as do the affected leaves. The disease takes advantage of weak points that often occur after a late frost. Commercially available preparations containing copper are used to combat it.
The pear gall midge lays its eggs in the blossoms, preferably on young pear trees. The hatched larvae migrate to the ovary and begin their harmful effects. Not only black spots appear on the affected pears. After some time, this can turn half or even completely black. It can also become wrinkled, decompose more and more and eventually fall off. There is currently no known effective remedy for the pear gall midge, so it is important to keep the infestation in check and avoid recurrence in subsequent years.
- pick off affected fruit
- collect fallen fruit immediately
- dispose of in the residual waste bin
- never compost
After about 4-6 weeks, the larvae pupate about 5-10 cm deep in the soil. If you loosen the soil, you can go on the tedious hunt for larvae. In rural areas, free-ranging chickens are good helpers in this regard, as they diligently pick up the larvae.
The risk of infection for this fungal disease is increased in a damp spring or early summer. It is prevented by thinning out the crown. Because of the better ventilation, fruits and leaves dry faster. If the fungus has nevertheless settled, you can recognize a severe infestation by these symptoms:
- first leaves get spots on both sides
- these are irregularly colored and brown-grey
- they keep getting bigger
- the foliage can die off and fall off as early as summer
- fruits also get black spots
- these are riddled with cracks
- the earlier the infestation occurs, the larger the spots
- early infected fruits may also fall off
Fungicides help against this fungal disease, but the spraying must be repeated several times.
infected flowers wilt and turn brownFire blight is by far the most dangerous cause of black discoloration. The disease is caused by a bacterium called Erwinia amylovora. It usually ends fatally for the pears. Only rarely do strong cuts have an effect after an infestation. Fire blight can be clearly recognized by the following damage pattern:
- they stay on the tree for a while
- young pears turn black starting from the stalk
- they gradually dry up
- Affected shoots dry up completely and turn black
- they hang down but don’t fall off
- Bacterial slime can escape in warm and humid weather
- it is first milk-colored, later brown
As soon as you notice the damage to your pear tree, you need to act quickly because fire blight is a notifiable disease in this country. Further measures are taken in coordination with the responsible office, mostly the clearing and subsequent destruction of the tree.
black spot disease
Black spot disease is a fungal disease caused by the fungus Stemphylium vesicarium. After an infestation, all leaves can show black spots. Even the fruit is not spared from this pathogen. Dark to black areas are visible on it, reminiscent of scab. The symptoms mainly appear on the shady and therefore wetter side of the tree. Combating black spot disease is not easy, but it is still possible.
- Remove all affected plant parts promptly
- Dispose of cut material safely
- Infested plant parts must not end up in the compost
- Thoroughly disinfect cutting tools before and after
- Then treat the tree with a suitable fungicide