Spots on spherical maple leaves
P: For 2 years, brown, round spots on the leaves appear on my spherical maples (7-8 years old). This disease does not cause leaf fall, although one of the clones has been systematically dying for two seasons. Are the stains on the leaves a harbinger of a gradual tree dieback? Is the dying off of one of my 6 clones possibly due to another disease? How and with what to fight stains on the leaves in the coming year?
A: The large, tarry spots on maple leaves in summer are a sign of disease caused by the fungus Rytisima acerinum. The source of infection are fallen leaves on which spores are formed.They are sown in spring, during the development of young leaves. Frequent rains contribute to the spread of the disease.
The disease can be prevented by collecting and burning fallen leaves, and in spring prophylactically spraying the trees - for the first time during the leaf development period, then 2-3 sprayings every 10-14 days with appropriate preparations.This disease does not kill the tree, but weakens it.
Gradual tree dieback may be caused by fungal diseases that destroy the tree. Infection occurs through damage to the bark (e.g. by insects, hail, frost, fractures or cuts).
Therefore, it is important that the wounds are lubricated with garden ointment mixed with fungicide within 24-48 hours of their inception.These measures are not effective, however, if the infection has already taken place.In order to take care of the remaining trees that are dying, they should be pulled down and their wood burned.
Yellowing of Korean fir needles
P: I have a teenage Korean fir that fell ill a year ago. At the ends of the young shoots, she began to turn yellow and shed needles.
A: Yellowing of young needles and their dropping may be caused not only by aphid feeding, but also by fir rust. In the event of aphids, the needles will additionally curl. Aphid spraying should be carried out immediately.The preparations should be used alternately, because the pests quickly become resistant.
The first series of spraying should be carried out in the period from the swelling of buds to the first growth of new needles at intervals of 7-10 days, while the second series in August / September.
The lack of sun in the lower parts of the tree can also cause needles to drop and the shadowed shoots to die off . Firs grow best in fertile soils and in positions with significant air humidity. A sick tree should be supported with fertilizers.
