Walnut blister mite

Walnut leaf gall mite (sometimes known as walnut blister mite) is a type of eriophyid gall mite. These gall mites are tiny (less than 0.2 mm) sap

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding. -sucking creatures that cause a variety of abnormal growths on various plants, they have whitish and elongated body and unlike most arachnids only have two pairs of legs. There are many species of eriophyid mite which are usually host specific this means that each species of mite will only feed on a single, or several closely related, plant species. Although the mites are too small to be seen without a microscope, the galled tissues that they create are often very distinctive and easily recognised. The excessive growth of hairs on the underside of leaves caused by some gall mites, including walnut blister mite, is called a felt gall or erineum.

Symptoms begin to appear in late spring. The upper surface of affected leaves bulges upwards, creating shiny yellowish green blisters between two leaf veins. Beneath the raised areas, a dense coating of short fine hairs develops, amongst which the mites live and feed. The hairs are usually white.

While the mites are sucking sap

Sap is a fluid that circulates through a plant's vascular system, in a similar way to blood moving through our veins. Phloem sap carries the sugars produced in the leaves by photosynthesis down to roots and other storage organs, as well as carrying minerals and hormones. Xylem sap is watery and transports nutrients absorbed by the roots upwards to the rest of the plant. Some plants leak sap from wounds or pruning cuts, and this is known as bleeding. , they secrete chemicals into the foliage that induces the abnormal growth. The hairy covering on the underside of the leaves could be mistaken for a fungal disease, such as mildew, but the mite is a not a problem. It does not affect the fruit and does not seem to have any harmful effect, apart from distorting the leaves.

The mites do not affect the fruiting or health of walnut trees and can be accepted as a part of the biodiversity

The variety of living organisms (plants, animals, fungi and microorganisms) in a particular environment. Boosting the biodiversity of your garden has many benefits, including supporting wildlife, improving soil health and reducing the likelihood of pest and disease problems. walnut trees support.
If the mite cannot be tolerated and only a few leaves or shoots are affected by galling, these can be cut off and disposed of. If many leaves are affected, the presence of the mite should be tolerated, as removing affected leaves will damage the tree.

Walnut leaf gall mites overwinter on walnut trees by hiding away beneath bud

A bud is a small, undeveloped shoot that contains the potential for new growth. Buds are typically found on stems, where they can be apical (found at the tip) or axillary (found between leaf axils) and may develop into leaves, shoots or flowers. scales. The mites emerge in spring and begin feeding on the new foliage. Several generations develop in the underside of the leaves during the summer. In late summer, the matted hairs created by the gall mites begin to dry up and this causes the mites to leave the foliage and seek places where they can overwinter.