These diseases can usually be controlled through the use of resistant varieties and proper culture. Leafspot is most serious on Kentucky bluegrass lawns when cool wet weather prevails, usually in the spring. Avoid high rates of nitrogen fertilizer in the spring. Raise your mowing height if you notice the disease. Contact Cornell Cooperative Extension - Suffolk County for cultivars of bluegrass and fine fescues that are resistant to leafspot.
Summer patch is a devastating disease that occurs during hot, dry periods.
Perennial ryegrass and several bluegrass varieties are resistant to this disease and should be included in a new seed or overseeding mixture. Summer patch is caused by a root pathogen. Therefore, any practice that encourages deeper rooting will make the lawn more tolerant to this disease, including proper pH and fertilization, proper mowing and irrigation. Red thread is a disease that is common during cool, wet periods in the spring. The grasses most affected are fine fescues and perennial ryegrass.