My Olive Tree has white 'froth' on it's lower branches - is it a disease or normal ?
Certified GKH Gardening Expert
This can be due to several different types of insect, and some fungi.
I would recommend applying neem oil to the tree on a cloudy day, to all of the portions that you can reach. Then apply wettable sulfur, and dolomitic lime. These will get rid of anything in the soil, while conditioning it and providing a few nutrients for common deficiencies.