Two common summer patch pathogens on fine fescues

By Jing Luo and Ning Zhang, Rutgers University

Summer patch is an economically important root disease on turfgrasses used on golf courses, sports fields, and lawns. It causes root, crown and stem rot that develop during periods of summer stress. Among the grass hosts, fine fescues are highly susceptible to this disease (Smiley et al., 2005). Magnaporthiopsis poae and M. meyeri-festucae are two commonly found fungi that cause summer patch disease on fine fescues (Landschoot and Jackson, 1989b; Luo et al., 2017).

Both fungal species are capable of causing root discoloration and biomass loss of the host grasses after colonization by producing ectotrophic, dark runner hyphae. However, they are different in morphology, biology and genetics (Luo et al., 2017). Magnaporthiopsis poae has a wide host range and was reported to infect the grass genera Agrostis, Festuca, Poa and Triticum. It is distributed widely in temperate regions of North America (Landschoot et al., 1993). It has a fast growth rate on potato dextrose agar where its colonies reach 6.8 cm diam after 7 days in the dark at 25 C (Luo et al., 2017). By contrast, M. meyeri-festucae is mostly associated with fine fescues. This species has limited distribution and has been only found in Maryland, Massachusetts, and New Jersey in the U.S. It grows slower than M. poae, with 4.5 cm diam colonies on potato dextrose agar after 7 days in the dark at 25 C (Luo et al., 2017).

Page from a monograph with four images of turf diseases
Figure 1. Front page of the Magnaporthales e-monograph.

Several other fungi have also been reported to be associated with summer patch disease on fine fescues and other cool-season grasses (Landschoot and Jackson, 1989a, b; Luo et al., 2017; Vines et al., 2019; Wong et al., 2015). All these species belong to the fungal order Magnaporthales. Their taxonomic, pathogenic, biogeographic and molecular characteristics are well documented in an e-monograph website of Magnaporthales that is being developed at Rutgers University (Luo and Zhang, 2021; Figure 1).

Understanding these summer pathogens will help turfgrass researchers identify control options and develop new summer patch-resistant cultivars.

References

Landschoot, P. J., Gould, A. B., and Clarke, B. B. 1993. Ecology and epidemiology of ectotrophic root-infecting fungi associated with patch diseases of turfgrasses. Pages 73–105. In: Turfgrass patch diseases caused by ectotrophic root-infecting fungi. B. B. Clarke and A. B. Gould, eds. American Phytopathological Society, St. Paul, MN.

Landschoot, P. J., and Jackson, N. 1989a. Gaeumannomyces incrustans sp. nov., a root-infecting hyphopodiate fungus from grass roots in the United States. Mycological Research 93:55–58.

Landschoot, P. J., and Jackson, N. 1989b. Magnaporthe poae sp. nov., a hyphopodiate fungus with a Phialophora anamorph from grass roots in the United States. Mycological Research 93:59–62.

Luo, J., Vines, P. L., Grimshaw, A., Hoffman, L., Walsh, E., Bonos, S. A., Clarke, B. B., Murphy, J. A., Meyer, W. A., and Zhang, N. 2017. Magnaporthiopsis meyeri-festucae, sp. nov., associated with a summer patch-like disease of fine fescue turfgrasses. Mycologia 109:780–789.

Luo, J., and Zhang, N. 2021. The rice blast fungus and allied species: a monograph of the fungal order Magnaporthales. Rutgers University. https://magnaporthales.sebs.rutgers.edu.

Smiley, R. W., Dernoeden, P. H., and Clarke, B. B. 2005. Compendium of turfgrass diseases. The American Phytopathological Society (APS) Press, St. Paul, MN.

Vines, P. L., Hoffmann, F. G., Meyer, F., Allen, T. W., Luo, J., Zhang, N., and Tomaso-Peterson, M. 2019. Magnaporthiopsis cynodontis, a novel turfgrass pathogen with widespread distribution in the United States. Mycologia 112:52–63.

Wong, P. T. W., Khemmuk, W., Geering, A. D. W., and Shivas, R. G. 2015. Magnaporthiopsis agrostidis. Persoonia 35:322–323.