Eriophyes is a genus containing over 200 species of mites. Different species target different plants, but its shrubs and trees which are mostly affected. The mites cause abnormal development which causes unusual growths to appear.
The mites are microscopic, less than 0.2mm in length and thus cannot be seen with the naked eye. They're more easily identified using the galls on plants.
From late spring through summer, tubular growths can be observed on infected plants. With gall mites, this shows up particularly on the leaves. Curling leaf edges, blisters, excessive hair growth and discolourment are common symptoms. Outgrowths up to 5mm long can be seen on the upper surface of leaves, these vary in colour across species. Gall mites also cause distorted plant growth.
Its recommended to prune damaged material back to where it looks normal as the first step of treatment. There is currently no control or prevention available.