Powdery mildew

Powdery mildew on oak

Powdery mildew can be found on the new leaves of oak trees during the summer. It is caused by a fungus called Erysiphe alphitoides and weaken trees by affecting the ability of leaves to photosynthesize.

Spraying the leaves with 5g potassium bicarbonate, 5g of olive oil, and 1 drop of liquid soap dilluted in 1L of water seems effective at controlling the infestation.