Fungi Associated with Spring Dead Spot Reduces Freezing Resistance in Bermudagrass

Abstract

<jats:p>Although the effect of cold winters on the severity of bermudagrass <jats:italic>(Cynodon dactylon</jats:italic> Pers.) spring dead spot (SDS) has been studied, information is needed concerning the effect of infection by fungi associated with SDS on the host's freezing resistance. A-22 bermudagrass was inoculated with <jats:italic>Leptosphaeria korrae</jats:italic> J. Walker &amp; A.M. Smith and <jats:italic>Ophiospharella herpotricha</jats:italic> (Fr.) J. Walker &amp; A.M Smith. Differential thermal analysis was used to monitor exotherm temperatures of healthy and <jats:italic>O. herpotricha-</jats:italic> and <jats:italic>L. korrae-</jats:italic>infected A-22 bermudagrass at 10-day intervals during 90 days of acclimation in cold chambers. Healthy bermudagrass crowns supercooled to an average of -6.7C and fungi-infected crowns supercooled to an average of -4.8 and -4.4C, respectively. Healthy crown exotherm temperatures were significantly lower than those of fungi-infected bermudagrass crowns on all nine sampling dates. This result indicates that fungi-infected plants are more susceptible to cold damage.</jats:p>

Effect of Cold Acclimation and Freezing on Spring Dead Spot Severity in Bermudagrass

“…We initially incubated plants at 4 °C for 30 days to reduce detrimental effects of freezing nonacclimated bermudagrass (Nus and Shashikumar, 1993;Rajashekar, et al 1983). However, SDS severity was greater in inoculated bermudagrass incubated at 4 °C compared to 25 °C.…”

“…All selections exhibited root discoloration but none developed shoot mortality typical of SDS and no differences among selections were detected. Nus and Shashikumar (1993) found that inoculation of bermudagrass cultivars with O. korrae increased the temperature at which freeze injury to roots occurred, and that the effect was more pronounced on the susceptible cultivar. Thus, exposure to freezing temperatures following fungal infection of roots might be a useful technique for screening bermudagrass selections for SDS resistance.…”

Zoysiagrass (Zoysiaspp.) History, Utilization, and Improvement in the United States: A Review

“…For example, in a severe winter in West Lafayette, IN, in 2013 to 2014, >50% winterkill was observed on large areas of two established, cold‐hardy bermudagrass cultivars (‘Patriot’ and ‘Riviera’), but <2% winterkill occurred on a large Meyer zoysiagrass fairway at the same site. Furthermore, unlike bermudagrass, which is susceptible to the hard‐to‐control disease spring dead spot ( Ophiosphaerella korrae Walker and Smith) that is most severe after cold winters (Nus and Shashikumar, 1993), zoysiagrass is not commonly damaged by this disease with the exception of a few isolated reports (Tisserat et al, 1994; Tredway and Butler, 2007).…”

Effect of Preemergence Herbicides on the Recovery of Bermudagrass from Spring Dead Spot

“…The germination of weeds in the center of disease patches may cause a decline in turfgrass aesthetic quality and reduce the playability of turf (20). In severe cases, bermudagrass may not fully recover from SDS symptoms before the onset of winter, leaving the turf susceptible to further damage from freezing temperatures (35,36).…”

“…may not fully recover from SDS symptoms before the onset of winter, leaving the turf susceptible to further damage from freezing temperatures (35,36).…”