We diagnosed our first cases of summer patch on creeping bentgrass putting greens in North Carolina last week. In case you are wondering, we haven’t seen many Pythium root rot samples. That will likely change if the heat stress continues with afternoon and evening thunderstorms.
The symptoms of summer patch on creeping bentgrass appear as circular patches or rings, ranging from a few inches to a foot in diameter. They often have the classic “frog-eye” symptom. Turf within these patches initially turns off-colored, is prone to wilt, grows poorly, and may appear sunken in the turf stand. Over a period of a few weeks, the turf continues to decline, turns yellow or straw brown and eventually collapses to the soil surface. The outer edges of the patch are usually orange or bronze when the disease is actively developing. The patches recur in the same spot annually, and can expand at a rate of 2 to 4 inches per year.
The summer patch fungus attacks the roots, stolons, and rhizomes in the spring when soil temperatures reach 65°F. Summer patch symptoms are rarely seen during the early stages of disease development, instead, the symptoms appear in mid-summer after considerable damage has been done to the root system. Heat, drought stress, and nutrient deficiencies are the main factors that encourage the expression of summer patch symptoms. In North Carolina, the symptoms typically appear in early to mid-July. For more information about summer patch, including control recommendations, click here.
We typically recommend about an 1/8 – 1/4″ post-application irrigation for summer patch, which in most cases equals about 3-5 minutes with part-circle heads. Either way, you may want to take the time to see how long it takes to put that amount out. This is a critical step towards maximizing your fungicide application.