Do you look after your elm conscientiously, do you water it regularly and provide a nutrient-rich substrate with fertilizer that is appropriate for the species? Nevertheless, the tree does not seem to be thanking you for your measures? In this case, your elm may be suffering from a pest infestation. Check your crop for the following pests.
The bladder louse makes ugly galls
The most common pests of the elm
The elm is mainly attacked by three pests:
- the gall mite
- the bladder louse
- the Dutch elm scale
The gall mite
An infestation of the gall mite can be determined comparatively easily. Knots reminiscent of toad skin are clearly visible on the leaves of entire sections of branches. With minor infestations, the elm only suffers passive damage, making it more susceptible to external factors such as weather and other diseases. However, their growth will not be affected. In order to remove the gall mite, it is advisable to remove the affected leaves immediately.
The Bladder Louse
The bladder aphid primarily infests field and mountain elms. The pests settle on the underside of the leaf. They cause conspicuous galls on the upper side of the leaf, which initially have a rich green color. The pustules only turn yellow in the course of the summer, before they turn brownish in autumn and finally dry up. The gall aphid does not cause any significant damage, but it does attract ants and makes the foliage appear unaesthetic. In summer it even flies out and infests surrounding grass. But once it has chosen an elm tree, it always returns to it to lay its eggs. Again, you should remove affected leaves.
The Dutch elm scale
You can recognize an infestation by the Dutch elm scale by a wreath of wax threads, which you usually find on young shoots. It almost looks like little snowflakes are lying on the wood. You free your elm from the pest with a legally approved pesticide.