Red thread is a disease of cool, wet weather, so it occurs mostly in the spring and fall. Round patches of light tan to pink-colored turf appear in the lawn, with pink webs binding the grass blades. On close inspection, you may see ¼- to ¾-inch-long pink threads at the tips. You see it most often on fine fescue and perennial ryegrass lawns in the Northeast and North Central states. However, Kentucky bluegrass, bentgrass, and bermudagrass may also be affected.