Advice - Parasites and diseases
Always remember that if your trees are cared for correctly, with regular
watering, proper lighting, they will be less susceptible to parasites
Many diseases result from old pruning wounds that were not properly protected and did not callus correctly.
We recommend the use of good quality grafting wax (Cut Pasta grafting wax with hormones, made in Japan).The commercially-available aerosol tars tends to cause irreversible burns.
Injuries caused by hail cause brown patches; if necessary, cut the plant back or put wax on any large wounds.
The Acer’s main enemies are aphids (green or black), especially on spring leaves. They can also be infested with spider mites or slugs.
We recommend using commercially-available insecticides, but the dosages must be strictly observed - don’t use too much.
It is a good idea to test the product beforehand, because some insecticides tend to discolour the foliage in the spring and can cause burns that remain visible all season long.
Bouts of powdery mildew in the spring or autumn (floury white formations on the leaf blades) can be dealt with as soon as they appear by using an appropriate fungicide.
Verticillium wilt is more serious. It appears on the trunk and branches, starting as small black spots which are then followed by withering of the branches, one after the other. Within 6 to 24 months, the tree dies. This disease is spread by pruning tools, or it can be present in leaves and branches lying on the ground, where the fungus can live for 12 to 15 years. There is currently no cure - the only option is to burn infected plants to avoid contaminating other Acers in your collection. Pay very close attention to the colour of the bark when buying your Acer, especially if the trees are imported from Korea.