In most places in the Midwest, the drenching rains have ceased (temporarily), allowing much of the turf to experience its first dry period during the 2015 season. The drought stress usually reveals all sorts of symptoms associated with root infection. On many swards of recently sodded Kentucky bluegrass, summer patch symptoms are in full glory (Figure 1). The characteristic patch symptoms above ground accompany root-infecting hyphae below ground (Figure 2). Plants whose roots are impaired by infection are the first to suffer from drought stress. Symptoms are apparent in juvenile (1- 3-year old) sod. Clearly, the “transplant shock” associated with establishing the sod on unfamiliar soil is partly to blame. It adds another layer of stress, making plants more prone to patch symptom outbreaks than mature sod and lawns established from seed.
Note that in this case, symptoms appear in a linear pattern, and are associated with strips of sod (Figure 3). Given that the entire site was prepared at once, and that the sod was harvested and laid in one day, it is likely that some of the sod was already infected when it arrived on site for installation.
There is no conclusive evidence that fungicides applied to symptomatic turf in mid-summer (when root growth is at a standstill) will hasten turf recovery. Any attempts to mitigate the damage with fungicide at this time should include a “check plot”—an area covered or left unsprayed to determine the real benefit of the spray.
Remember that fungicides effective against root diseases (summer patch, necrotic ring spot, take all patch, or spring dead spot) will not move downward through the plant to the roots. On higher (2”-3”) cut turf, post application irrigation will help move fungicide into the thatch layer.