Frequent soil surfactant applications influence anthracnose on an annual bluegrass research green

Abstract

AbstractAnthracnose is a turfgrass disease caused by the fungal pathogen Colletotrichum cereale Manns and can cause severe damage to annual bluegrass putting greens. Most turfgrass managers use fungicides to manage anthracnose, although legislation in some locations are compelling managers to seek fungicide alternatives. This 2‐yr field experiment in western Oregon evaluated different rates and application intervals of a soil surfactant—either in combination or in the absence of a spring hollow‐tine aerification on anthracnose severity—on an annual bluegrass (Poa annua L. var. reptans) research green. The highest rate of the soil surfactant applied once or twice a week consistently reduced anthracnose severity in both years compared to the nontreated control, although these applications corresponded to four and eight times the monthly label rate. A quarter of the label rate applied once a week suppressed anthracnose at the peak of disease in the second year and as measured by area under disease progress curves in both years. Spring aerification had no effect on anthracnose severity. Area under volumetric water content progress curves calculated using weekly measurements at a 38‐mm depth were not correlated with area under disease progress curves. The volumetric water content percentage was normally above 25%, reducing the risk of confounding between drought stress and treatments on anthracnose suppression. The highest rate of soil surfactant applied at the most frequent interval was the only treatment to receive acceptable turfgrass quality ratings over both years.