Effect of Mowing Height on Crabgrass (Digitaria spp.) Incidence in Turf.

Tall fescue (Lolium arundinaceum) and common bermudagrass (Cynodon dactylon) are widely used in North Carolina (NC) turf areas including golf courses, home lawns, commercial properties, and athletic fields.  Large crabgrass (Digitaria sanguinalis) and smooth crabgrass (Digitaria ischaemum) are two of the most troublesome weeds that homeowners and turfgrass managers must contend with when managing these turf species.  These common weeds can become a major problem because of their ability to establish and reproduce quickly, especially in less dense turf stands.  Field experiments were conducted during 2007 at two locations (Sandhills Research Station, Jackson Springs and Lake Wheeler Field Labs, Raleigh) to determine if turf mowing height could suppress large crabgrass in common bermudagrass and confederate blend tall fescue (Council, North Carolina).  The Raleigh location consisted of an Appling fine sandy loam and the Jackson Springs location consisted of a Candor sand.  Large crabgrass from Okeen, Oklahoma was seeded in each experiment in early March.  Evaluated mowing heights included 1.27 cm, 2.54 cm, 3.81 cm and 5.08 cm for common bermudagrass and 2.54 cm, 5.08 cm, 7.62 cm and 10.16 cm for confederate blend tall fescue, which were initiated once soil temperatures reached an optimum for crabgrass emergence.  In bermudagrass, no significant differences (P = 0.05) were discerned among mowing heights or locations.  However, there were significant differences in tall fescue in Raleigh, with mowing heights of 2.54 cm, 5.08 cm, 7.62 cm and 10.16 cm resulting in 95%, 48%, 13%, and 0% crabgrass cover, respectively, by early-September.  While the Jackson Springs location contained 79%, 74%, 31%, and 0% crabgrass cover, respectively, with mowing heights of 2.54 cm, 5.08 cm, 7.62 cm and 10.16 cm.  This shows that the growth habitat of tall fescue can be used to help suppress large crabgrass by implementing the correct mowing height.