// The Problem
Anthracnose, caused by the pathogen Colletotrichum cereale, can be a severe disease of intensely managed annual bluegrass and creeping bentgrass surfaces. The disease is most common on putting greens and occurs predominately in mid-summer under hot/humid conditions or in the fall-spring months under cold wet conditions. Foliar blighting develops on older leaves first and is most common in the summer. Basal anthracnose can develop from foliar blighting or independently during periods of cold, wet weather. Since it often occurs when turf growth potential is low, recovery from anthracnose can be difficult.
// What to Look For
Symptoms on annual bluegrass can develop as irregular patches of chlorotic turf that progress to a yellowing to orangish colour in advanced stages. Affected areas begin as patches a few centimetres in size and can coalesce into large blighted areas. Black acervuli with hair-like setae are distinctive signs of anthracnose; mycelia are not produced on the outside of the plant. Acervuli can be found on the older senescent leaves first, but can be present on green tissue in advanced stages of disease. Plants affected by basal rot have a black discolouration of the stems and crowns; acervuli may not be present when the disease develops under cold conditions.
Anthracnose can also occur on creeping bentgrass putting greens and fairways during the summer months. Older cultivars grown under low nitrogen inputs are most susceptible to infection. Unlike the yellowing observed with annual bluegrass, creeping bentgrass affected by anthracnose tends to be more bronze in colour. Due to this, scouting for anthracnose on bentgrass surfaces tends to be more difficult compared to annual bluegrass.