Cream leaf blight of dwarf bermudagrass

Cream leaf blight of dwarf bermudagrass


Figure 1. When applied to bermudagrass, the symptoms of cream leaf blight begin as small white or cream spots or spots that are 3 to 8 inches (7.6-20.3 cm) in diameter. Photo by Lee Butler


Cream leaf blight was discovered in tall fescue plots in Georgia by university researchers who isolated it Limonomyces rosebillis Tall fescues develop white lesions extending towards the base of the leaf. In tall fescue landscapes, turmeric leaf blight is rare, however the fungus affects dwarf bermudagrasses extremely (Cynodon dactylon × C. transvalensis) planted on a golf course and putting green as well.

Little is known about the disease that affects Bermuda plants, but we commonly see it in the transition zone and even in northern Florida. However, this disease is more prevalent in areas where bermudagrass is dormant. The disease has emerged in the Southeast as a result of the shift from creeping bentgrass (Agrostis stolonifera) Increased putting greens on extremely dwarf Bermuda grass.

We suspect that the disease has been around for some time and was likely diagnosed as a superficial fairy ring, pink patch, or some other basidiomycete fungus. While golf course superintendents were working on winter management practices, leaf blight was a concern, because it can spread over large areas of greens quickly, yet the disease appears to have caused no serious damage.

Symptoms and signs of cream leaf blight

When applied to bermudagrass, symptoms begin as small white or cream spots or spots ranging in size from 3 to 8 inches (7.6-20.3 cm) in diameter (Figure 1 above). The spots rarely increase in size, but may cluster in larger areas. The disease is cosmetic, as we observed little permanent damage associated with the disease, however it can affect large areas of turf. It may be difficult to see standing symptoms when painting or staining Bermuda grass during the winter months. Symptoms have been observed throughout the evergreen region during the winter months.

Affected leaves have a cream to white appearance, but no visible lesions can be found on the leaves. There are no noticeable symptoms or signs of root or root recession. Unlike pink spot disease and some other fungal diseases, aerobic fungi have not been observed in this disease.

Cause of cream leaf blight

The pathogen is Limonomyces rosebillis, the same organism that causes pink spot in cool-season grasses. However, the biotype associated with skim leaf blight does not produce stipule connections and does not have a pink or reddish appearance on the leaf.

Limonomyces rosebillis
Figure 2. Mushrooms Limonomyces rosebillis Hyphal aggregates are produced after incubation of Bermuda samples. Hyphhal aggregates are only visible with a dissecting microscope.


The fungus readily produces hyphal aggregates after incubation of Bermuda samples, with no apparent synapse connections (Figure 2, above). The hyphae themselves are hyaline and diploid. In our experience, the fungus sometimes grows easily from leaf tissue after 24 hours, but at other times, it is slow to produce diagnostic hyphal aggregates.

Conditions favorable to the disease

Mushrooms are able to grow in a wide range of temperatures. Mushroom growth has been observed from 40°F to 90°F (4°C to 32°C), but optimal growth in culture ranges between 68°F and 77°F (8°C to 20°C) (3). However, the biotype observed on very dwarf bermudagrass appears to grow best in the lower temperature range. In particular, cream leaf blight is most dangerous on bermudagrass that has been mulched during the winter months. This fits the description of the fungus, as it is usually more dangerous when the grass is slow growing, as it is a slow growing fungus. Although the disease is more prevalent during the winter, we have observed it in the summer during long periods of rain and cloud cover.

Management of cream leaf blight

Management of cream leaf blight has been relatively simple. Fungicides work well, and a few have been exceptional in our experience. Cream leaf blight had not developed in any of our fungicide trials until 2016, so before then we relied on supervisors' feedback about what was working. A number of people have reported that iprodione works well therapeutically. Therapeutic applications are made after significant standing symptoms appear. Several supervisors said Prostar (flutolanil, Bayer) was also excellent. One supervisor reported spraying a combination of iprodione and Prostar, which quickly eliminated the disease. If therapeutic applications are warranted, do not water the products, as the fungus harbors itself in the foliage. Other fungicides may also be effective, but we have not conducted a treatment trial for this disease.

Management of cream leaf blight
Figure 3. Preventative applications of fungicides in the fall usually work very well against cream leaf blight.


Preventive applications work very well against cream leaf blight (Figure 3). We collected this data mainly in our dead spring experiments. Typically, we make these applications in the fall when soil temperatures drop to 70°F (21°C), and we make a follow-up application 28 days later. The past three falls, we haven't reached these soil temperatures until mid to late October. In our tests, all applications are irrigated immediately with 0.125 inch (3.2 mm) of water. Velista Applications (pentiopyrad, Syngenta); Lexicon (Floxapyroxad, BASF); Gib (chlorothalonil, iprodione, thiophanate methyl, tebuconazole; Quali Pro); Presquay (azoxystrobin, difenoconazole, Syngenta); Progression (azoxystrobin, propiconazole, Syngenta); STROBE (Azoxystrobin, Quali-Pro) + propiconazole; Popular T (Floxastrobin, Tebuconazole, FMC); and Torque (tebuconazole, Cleary Chemicals) all suppressed cream leaf blight when it developed in January and February in untreated controls. However, tebuconazole and other demethylation inhibitors did not provide consistent control in our experiments. In one trial, tebuconazole suppressed cream leaf blight, but in an adjacent trial, it was unable to control the disease (2).

It is worth noting that the last applications performed in many of these experiments were around November 15. Therefore, supervisors will control cream leaf blight with fungicides that target spring dead spots. We're not sure if applications targeting systemic root rot will control cream leaf blight, although they likely will, as the timing seems to align well with spring dead spot. However, we did not observe activity of Tartan Stressgard (trifloxystrobin, triadimefon; Bayer) on cream leaf blight, although it was an excellent preventive treatment for systemic root rot. Fortunately, we have seen excellent results with other powerful root rot products such as Lexicon and Briskway. Phosphite may also limit disease progression, but we currently have no data to support this assumption.

Little is known about the cultural management of cream leaf blight. We believe we will not learn more about the biology of these fungi until they become a bigger problem. Since the disease is more prevalent during the winter, especially on slow-growing or dormant grass, fungicides may be the best option for managing it.

Currently, we suggest that maintainers apply fungicides in the fall to control spring dead spot and root rot, as these diseases can be devastating. Based on these applications, other fungicides may be warranted as green bermudagrass is covered during periods of extreme cold. Typically, we suggest using chlorothalonil, iprodione or mancozeb before covering the greens to ensure that fungi do not multiply under the covers.

Cream leaf blight is an interesting disease of Bermuda grass that sets evergreens and tall landscapes. It is a relatively minor disease of evergreens, but it can spread over large areas quickly. Disease remains a cosmetic problem, but often relatively minor diseases can become more problematic as environmental conditions or management practices change over time.

Superintendents who suspect skim leaf blight on their golf course should submit a sample to a local diagnostic laboratory. After correct diagnosis, management of this disease becomes straightforward. However, get a diagnosis, because white spots on Bermuda grass are symptoms of many different diseases. Symptoms of crepe leaf spot may be confused with systemic root rot or the primary symptoms of spring dead spot or root-knot nematode.

Finance

This work is supported by the Turfgrass Research and Education Center at North Carolina State University and the North Carolina Agricultural Research Station.


Research says…

  • Cream leaf blight is a disease of extremely dwarf bermudagrass caused by a pathogen Limonomyces rosebillisthe same organism that causes pink spot in cool-season grasses.
  • Although patches of diseased grass may quickly cover the lawn, the disease is largely cosmetic and causes little permanent damage.
  • The fungus can be seen in a wide range of temperatures, but grows best at lower temperatures (40°F) and is most winter hardy on bermudagrass protected by a green cover.
  • Many common fungicides provided good preventative control when applied in the fall. No therapeutic trials have been conducted.

Literature cited

  1. Burpee, L. L., C. W. Mims, L. B. Treadway, J. Bai, and J. Jung. 2003. Pathogenesis of the new biotype Limonomyces rosebillis In tall fescue. Plant diseases 87:1031-1036. doi:10.1094/PDIS.2003.87.9.1031
  2. Kearns, J. P., L. Butler, M. D. Soyka and J. N. Ploetz. 2017. Effects of Fellista and Brisque programs on controlling spring dead spot on green bermudagrass, 2015-2016. Plant disease management reports 11:T020.
  3. Smiley, R. W., P. H. Dernwedden, and P. B. Clark. 2005. Compendium of Turf Diseases. American Phytopathological Society, St. Paul, Minnesota.

Jim Kearns is Associate Professor and Lee Butler is Extension Coordinator in the Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina.

    (tags for translation)Cream Leaf Blight

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