Tech Notes Issue 20

Sand Topdressing and Its Association with Summer Greens Management and Anthracnose

With summer stress season just around the corner, concern arises over management practices that may contribute to the stress of cool season putting green surfaces. Recent research out of Rutgers University USA has shed new light on management practices and their influence on anthracnose. 

Anthracnose caused by the fungus Colletotrichum cereale is a serious disease of wintergrass (Poa annua) and to a lesser extent creeping bentgrass (Agrostis stolonifera) during the summer. Anthracnose is a destructive disease of weakened or stressed plants. Management practices can either enhance or alleviate the severity of anthracnose (1).

Topdressing, the light frequent application of sand to putting green surfaces has often been associated with increasing the severity of disease. The logic goes that abrasions caused by sand particles and mowing induce leaf wounds that the anthracnose pathogen can enter. Regarding leaf wounds, recently researchers reported that anthracnose can easily infect unwounded leaves (3). In turf, anthracnose does not need a point of entry. It can easily infect stressed or dying plants without any help.

Topdressing studies at Rutgers looking at different rates (0, 0.3, 0.6, or 1.2 L m^-2) application interval (7, 13, 21, 28 or 42 day) found no increase in anthracnose with topdressing. Actually, as the study progressed through the season (study went for 2 years) anthracnose severity was reduced with topdressing compared with the no topdressing
treatment (2).

At first glance these results would appear to be opposite of what we might think. It appears that topdressing helps reduce anthracnose by providing a firmer surface, causing the mowers to actually mow at a slightly higher cut (reducing plant stress) than where topdressing is not applied.

References

1. Inguagiato, J.C. J.A. Murphy, and B.B. Clarke. 2008. Anthracnose severity on annual bluegrass influenced by nitrogen fertilization, growth regulators, and verticutting. Crop Science 48:1595-1607.

2. Inguagiato, J.C., J.A. Roberts, J.A. Murphy, and B.B. Clarke. 2008. Determination of sand topdressing rate and frequency effects on anthracnose severity of an annual bluegrass putting green. Proceedings of the seventeenth annual Rutgers Turfgrass Symposium. pp. 44- 46.

3. Vernard, C. and L. Vaillancourt. 2007. Penetration and colonization of unwounded maize tissues by the mais anthracnose pathogen Colletotrichum graminicola and the related nonpathogen C. sublineolum. Mycologia 99:368-377.

Photograph: Colletotrichum cereale (formerly C. graminicola) spore (center stained) with associated infection structures (appressorium) (dark structures).  The pathogen does not need a wound entry point to cause infection.