Mushi taji

When I visited Japan last year, I was puzzled by small straw mats tied around tree trunks (see the image above). Is this a horticultural technique? Is it a religious custom? Or is it just a garden ornament? I stumbled across the answer in a wonderful book on Japanese gardens by Motomi Oguchi. This straw mat is called mushi taji. It is put in autumn when insects descend from the canopy down the trunk to the ground for overwintering. Mushi taji tricks insects to overwinter in it and at the end of winter it is burnt. A more elaborate version of it, called fuyugakoi, is used in colder parts of Japan to protect the trees from frost and retain moisture in the soil, in addition to pest control. Fuyugakoi can be quite decorative as well.