Strategies to Increase Bermudagrass Recovery…

Strategies to Increase Bermudagrass Recovery from Spring Dead Spot Damage

By Wendell Hutchens, Mike Goatley Ph.D., and David McCall, Ph.D.

Spring dead spot (SDS) is a challenge to manage in Virginia. Most research efforts for SDS are geared toward employing preventative practices such as fungicide applications and other cultural practices in the fall while recovery strategies from damage in the spring and early summer are often overlooked. Preventative practices can be effective, but they are often inconsistent, so further investigation into optimizing bermudagrass recovery from SDS damage in the spring/early summer is necessary.

A field trial was conducted from 24 May 2019 to 2 August 2019 and repeated the following year from 25 June 2020 to 6 August 2020 on ‘Patriot’ bermudagrass in Blacksburg, VA. There were six treatments in the study:

1) nontreated control (NTC)

2) two applications of urea two weeks apart totaling (2 lbs N -M ) (U)

3) verticutting

4) solid-tine aerification (SA)

5) verticutting + two applications of urea two weeks apart totaling (2 lbs N -M ) (U + V) and

6) solid-tine aerification + two applications of urea two weeks

Plots were rated for percent necrosis throughout the study. Data were analyzed as percent necrosis change relative to initial assessment to measure bermudagrass recovery from SDS damage.

The main effect of cultivation reduced bermudagrass recovery by 33 and 12 percent units in 2019 and 2020, respectively (Fig. 1). In contrast, the main effect of fertility increased bermudagrass recovery by 22 percent units in 2019 while no difference was observed in 2020. On 07 June, 26 Jul, and 02 Aug 2019 there were treatment effects on bermudagrass recovery (Fig. 2). On 07 June 2019, SA reduced bermudagrass recovery by greater than 57 percent units compared to all other treatments except for U and U + V. Moreover, on 26 Jul and 02 Aug 2019, the U treatment improved bermudagrass recovery by at least 93 percent units compared to the V and SA treatments. In 2020, there were treatment effects on 02 Jul and 02 Aug 2020 (Fig. 3). On 02 Jul 2020, the NTC and U treatments improved bermudagrass recovery by greater than 38 percent units compared to the U + V and U + SA treatments. On 02 Aug 2020, the U treatment improved bermudagrass recovery by more than 22 percent units compared to the V and SA treatments.

FIGURE 1: Main effect across all assessments of fertility or cultivation on mean percent necrosis change relative to percent necrosis at initial assessment. Data were separated by year (P < 0.0001).

FIGURE 2: Percent necrosis change relative to percent necrosis at initial assessment in 2019. Data were analyzed by rating date (P < 0.0902).

FIGURE 3: Percent necrosis change relative to percent necrosis at initial assessment in 2020. Data were analyzed by rating date (P < 0.0847).

This study suggests that urea applications alone in the late spring/early summer are sufficient for optimizing bermudagrass recovery from SDS damage. In contrast, cultivation practices such as verticutting and solid-tine aerification without fertility are not sufficient to increase bermudagrass recovery from SDS damage. Our recommendation is to fertilize with 2 lbs N -M in the spring if bermudagrass is suffering damage from SDS. The benefit traditional cultivation practices such as verticutting and aerification have in other areas of turf management (i.e., thatch reduction, increased oxygen to the rootzone, etc.) warrant their use, but they may be better suited for mid-summer employment on bermudagrass after SDS is sufficiently recovered. Future research will focus on other cultivation methods as well as the effect of various fertilizer types on bermudagrass recovery from SDS.