Hemp russet mite (Aculops cannabicola)
Pest description and crop damage Hemp russet mites (Acari, Family Eriophyidae) are elongate and very tiny, much smaller than spider mites, with adults being 0.2 mm in length. These mites have two pairs of legs located towards the head. This mite can build up to high populations, especially in greenhouses. The most common crop damage is foliage becoming off-color but curling of the leaf edge and stunting of bud growth have been reported. It has been reported west of the Cascade.
Biology and life history The hemp russet mite is not well-studied but it is in the same genus as the tomato russet mite. The life cycle can be completed very rapidly under optimal conditions. These mites most likely stay on hemp plants continuously in the greenhouse environment. It is not clear if they have a dormant or semi-dormant stage and if they can successfully overwinter outdoors.
Scouting and thresholds Hemp russet mites can be observed by scanning the underside of the leaves with high magnification. There are no established treatment thresholds for hemp russet mite.