The GARDENA gardening expert
Dear Ms T. – that is an unusual phenomenon! Woodlice do like to crawl under dead tree bark, but otherwise they prefer to be close to the ground, living in covered, damp places and eating mouldy plant remains. They eat living plant material more rarely, for example young seedlings, under the propagation trays of which they are often found. But apples? An interesting occurrence! So what can you do?
By dint of their biology, woodlice are definitely dependent on a damp environment. In my opinion, this could be the approach for a solution: first check whether the bark of your apple tree is damaged, with dead areas or cracks. Woodlice like to set up home in such places, so remove all these areas (brush them down using a wire brush, then close the wounds and care for them using artificial bark as required). In addition, search for further possible living quarters for woodlice in direct proximity to the tree and remove them – as they can migrate from here and thus increase the infestation intensity.
A wide, airy tree crown assists in avoiding a humid microclimate – woodlice will avoid dry areas. Therefore, professionally-conducted pruning can also be helpful. This consideration must also be applied to the surrounding area: this, too, must be cleared and pruned back enough so that the garden is well-ventilated without draughts, in order to air and prevent excessively high air humidity (e.g. after dew or rain) in good time.
As soon as the tree has been freed of woodlice, you then have the option of forming a collar using a sheet metal strip and applying this all around the apple tree trunk without a gap, one hand-width above ground (readjust every year to stop it digging into the growing tree)! If the collar is moulded into the same shape as a slug fence, the crustaceans should find it difficult or even impossible to conquer the tree again.