How exactly does an arid environment promote the disease?
The virus is spread, or vectored, by wheat curl mites. Wheat curl mites, Asceria tosichella Keifer, are very small mites; <1/100 long, they are not visible to the unaided eye and require a dissecting scope or 10X 20X hand lens to see. They are whitish yellow, have an elongated tear-drop shape, and have 4 legs near the head that provide only limited movement and a sucker-like structure at the end of their abdomen. They use this structure to attach to leaves and to stand upright on a leaf to catch winds for dispersal. Their complete life cycle (egg, 2 larval stages, and adult) takes only 7-10 days resulting in rapid population growth. They feed only on green plants and if none are available at hatching, wheat curl mites will die. It is unusual to have large populations of wheat curl mites develop in Minnesota. Although they dont have wings, wheat curl mites can be dispersed by wind. Because they require an adequate food source within 24 hrs, dispersal distance is generally limited (a few
