Oak trees covered in black soot and rain sticky dew?
Why are the oaks covered in black soot and rain sticky dew?
Oaks have been plastered this year by a fungal disease called sooty mould. This disease is associated with small aphids which lodge under the oak leaf. These insects suck the leaves and give off a sticky “honeydew”. The combination of black sooty mould and stickiness messes furniture, cars, roofs paving etc that happens to be underneath the tree.
This is strictly a summer problem. No leaves means no problem. The infestation is seasonal and is associated with the current weather conditions.
Preventative treatment IS possible though. On smaller trees, jetting the aphids off with water can work. On larger trees, spraying is not so effective because of the difficulty of covering the whole canopy. The chemical Imadoclorpyr marketed as Koinor can be applied as a soil drench in early spring and again in November and in March. This product is absorbed through the roots and taken up right into the canopy. Contact Margie Nel 082 6853453
Bio friendly products include Neem oil which can be sprayed as a 1-2% solution but is less effective.
Long term solutions focus on improving soil health thereby enabling the tree to fight the problem itself.
For further advice and/or help with your trees, please contact one of the tree companies listed on our website.