Midseason cultivation effects on anthracnose of annual bluegrass turf.

Mechanical injury from cultivation practices is reported to enhance anthracnose disease, caused by the fungus Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman, of annual bluegrass (ABG) [Poa annua L. forma reptans (Hausskn.) T. Koyama]. Two field experiments were initiated with the objectives of determining the effects of midseason cultivation practices (Experiment 1) and scarifying depth (Experiment 2) on anthracnose severity of ABG maintained at a 3.2‐mm mowing height on a Nixon sandy loam in North Brunswick, NJ. Experiment 1 treatments consisted of grooming, verticutting, scarifying, and solid‐tining every 21 d as well as weekly grooming and no cultivation over 2 years. Experiment 2 evaluated single treatments of shallow and deep scarifying and a nontreated control in three runs. Verticutting increased the area under the disease progress curve (AUDPC) compared with no cultivation during the first year, whereas verticutting and scarifying increased AUDPC relative to no cultivation during the second year. No other cultivation treatments differed from the control during either year in Experiment 1. In Experiment 2, scarifying did not increase AUDPC during any run at either depth. Results from these experiments indicate that cultivation practices that affect at least 15% of the turf surface area and injure crowns may increase anthracnose severity, whereas practices that affect a smaller turf area or only leaf tissue will not increase disease severity. [ABSTRACT FROM AUTHOR]