Rust is a disease that is common on Kentucky bluegrass and perennial ryegrass in the fall. It is a disease that is favored by low nitrogen fertility levels. Fall fertilization should prevent rust from ever being a problem. Snow mold is one of the more serious diseases in upstate New York. The symptoms of snow mold are not usually noticed until after the snow recedes in the spring.
Snow mold is a winter disease that is enhanced by succulent growth.
Proper fertilization in the fall with nitrogen and potassium should help keep the damage to a minimum. Timing of application is most important. Avoid fertilizer applications after October 1 and before the last mowing. Fertilizer can be applied after the last mowing, usually in early to mid-November or later on Long Island. Some natural organic fertilizers and compost will suppress and sometimes prevent disease problems.