Ink stain on golf course grass
Figure 1. Powerful, black mycelium of Corvularia malina Colonization of infected stems and leaves of bermudagrass and zizia grass can be observed. Photography by Maria Tommaso Peterson
In the late 2000s, golf course superintendents in the greater Houston area were seeing leaf patch disease on bermudagrass, zizia grass, tea boxes and fairways. Because the initial symptoms of the disease were small, dark brown-black spots, the disease was given the name “ink spot.”
During that period, Mississippi State University received a diagnostic specimen taken from a bermudagrass (also known as 328 or Tifton 328), which is green with a distinctive chocolate brown patch in the grass canopy. Black spots appear on the leaves. The symptoms in the diseased grass sample were different from any I had observed.
Infected leaves were placed on water agar, a nutrient-deficient medium that promotes fungal proliferation. Within 36 hours, the pathogen’s powerful black fungus was growing from the leaf tissue. In pure culture, the fungus was black and sterile; No reproductive structures have been developed that would aid in fungal recognition.
In the same growing season, specimens of this apparent disease were received from bermudagrass, tee boxes and fairways as well as zoysiagrass fairways. In the following years, turf pathologists at Mississippi State University and Texas A&M University independently isolated a dark-colored sterile fungus from lesions associated with the chocolate brown to black spot occurring in golf course specimens from the region.
right: Figure 2. Foliar symptoms of ink spot on zoysiagrass path. A: Ink spot first appears as chocolate brown to black spots ranging in size from 1 inch to 6 inches (2-15 cm). B: Under ideal disease conditions, ink spot symptoms may cluster, creating large areas of brown to black mottled grass. Photos by Billy Weeks
Dr. Young Ki Joo of Texas A&M University and I have begun a collaborative effort to characterize the inkblot and its undescribed causative agent. As samples arrived at the laboratory, our live culture population increased. However, because fungal pathogens are sterile, we used molecular methods for identification purposes.
Amplification of the universal DNA barcode gene of fungi, the ribosomal internal spacer (ITS) region, was the first step toward identification. The amplified ITS product was sequenced and uploaded to GenBank, a genomic sequence database. The primary ITS match was an undescribed fungal pathogen from Japan associated with dog print disease of zoysiagrass.
In the 1997 book Color Atlas of Turf Diseases (1) A foliar disease of zoysiagrass in Japan has shown symptoms in turf similar to those of ink spot in the United States. It was identified as Corvularia blight. Among the pathogens associated with Curvularia blight is a black sterile fungus that is not fully described in the book. Over time, we received photographs and samples of inkblots from golf courses in Alabama, Mississippi, Tennessee, and Hainan Province in China, expanding our understanding of the disease’s distribution. Because the sterile fungal pathogen causing inkblot has not been described, a comprehensive phylogenetic analysis was performed, leading to the identification of a new fungal species ( 2 ).
The pathogen of inkblot
A new kind of curve It has been identified as the foliar pathogen of bermudagrass and zysia grass in the southeastern United States (2). Corvularia malina sp. November. (meaning “black”, “dirty”, “coloured”) refers to fungi and symptoms found in turf. Black web-like mushroom C- Berries They can be observed under low magnification on the outer surface of infected leaves and stems (Figure 1, top).
As shown, the fungus is sterile, and therefore does not develop any asexual conidia, unlike its very distant relatives. C- Crescent And C. geniculataIt is a prolific producer. Optimum temperature for growth C- Berries It is 77 F (25 C). The fungus reproduces under ideal temperature and humidity conditions, allowing rapid identification on farm.
Symptoms and climatic conditions suitable for ink spot
Figure 3. Foliar symptoms of ink spot caused by Corvularia malina These include clear oval lesions with black margins on zizia. Lesions may expand across and below the leaf to cause blight. Photography by Maria Tommaso Peterson
Ink spot on bermudagrass and zizia grass managed under golf course conditions appears as clear, chocolate brown to black spots ranging in size from less than 1 inch to 6 inches (2-15 cm). As the disease progresses, the spots coalesce to form large, irregular areas of affected turf (Figure 2). Leaves of affected plants initially display small purplish-black spots that develop into characteristic ocular lesions with dark brown, necrotic centers surrounded by dark brown-black margins (Figure 3). Old, shredded leaves in the lower canopy of the grass cause noticeable chocolate brown to black spots in the grass stand. Spots resulting from fall outbreaks may remain evident within dormant grass, maintaining a sooty black appearance until spring greens (Figure 4 below).
Figure 4. During fall ink spot epidemics, generous black spots may remain in the grass canopy throughout dormancy and recur during spring green-up. Photography by Maria Tommaso Peterson
Ink spot is most prevalent in spring and fall, which are transitional periods for bermudagrass and zizia grass, but the disease may persist into the summer months following prolonged or large rainfall events such as tropical storms or hurricanes. “Corvularia blight” or “dog footprints” (inu no ashiato; Japanese translation) are turf diseases caused by the same pathogen, C- Berriesas Micah Woods, Ph.D., concluded in the Asian Grass Center blog (3).
Anecdotal observations and first published report (Hainan Province, China) of the disease caused by… C- Berries It seems to indicate that diseases caused by C- Berries It is geographically limited to areas affected by the subtropical ridge associated with 30 degrees north latitude. Latitude 30 north is considered dry to semi-arid, but areas in that region affected by large bodies of water have a more tropical environment and form the so-called “subtropical range”. These regions include the Gulf and Atlantic Ocean of the United States, southern China, southern Japan, and southern Queensland, Australia. Currently, no ink spot has been reported beyond 30 north latitude.
Inkblot host species
To end the description C- Berries and inkblot, a host-scale study of warm-season grasses was conducted at Mississippi State University. In greenhouse studies, zysia grass was more susceptible to infection than all other warm-season grasses evaluated, including bermudagrass.
Figure 5. Cause of sickness Corvularia malina For warm-season grass species: zoysiagrass (top), centipede (middle) and seashore paspalum (bottom). All three pictures show seedlings in C- Berries– Infected (left) and uninfected (right) potting mix five weeks after planting. In all three cases, seedling density decreased C. Malina infested Soil. Photos by Maria Tommaso Peterson
Centipedes and St. Augustine grass had foliar blight, but foliar blight was not widespread. Seashore paspalum did not develop foliar lesions, but the dry weights of shoots and roots were significantly reduced compared to screening (Figure 5.) Currently, field symptoms of ink spot have only been observed on bermudagrass and zizia grass, the latter of which appears to be more susceptible in the southern U.S. .
Golf course superintendents have successfully managed ink spot with labeled fungicides curve Classify. However, efficacy trials that include new generation succinate dehydrogenase inhibitor (SDHI) fungicides as well as fertility studies that include nitrogen source and rates may benefit supervisors trying to reduce inkblot outbreaks caused by C- Berries.
This research is a contribution from the Mississippi Agricultural and Forestry Experiment Station and the USDA National Institute of Food and Agriculture, Hatch Project under accession number 213130.
Thanks and appreciation
We are grateful to all of the Houston golf course superintendents who provided turf samples for ink stain diagnosis and characterization Corvularia malina.
- A disease affecting warm-season grasses was discovered in the Houston area in the late 2000s.
- Because the disease’s initial symptoms were spots in the grass ranging from dark brown to black with black leaf lesions, the disease was given the name “ink spot.”
- Genetic analysis was used to identify the fungal pathogen of inkblot, which was considered a new pathogen and named Corvularia malina.
- The ink spot is only found at latitude 30 north.
- More research is needed to identify management practices or products that will reduce or control disease incidence.
- Taney, T., and J. B. Baird. 1997. Color Atlas of Turf Diseases, First Edition. Ann Arbor Press, Chelsea, Michigan.
- Thomas Peterson, M., J. Young, K., B. L. Vines, and F. J. Hoffman. 2016. Corvularia malina sp. November. A new disease affecting warm-season grasses in the southeastern United States. mycology 108(5):915-924.
- the forest. M.2016. Dog imprinting and susceptibility of grass to this disease. Viridescent: Asian Turf Center Blog. September 19, 2016.
Maria Tommaso Peterson is a research professor of plant pathology at Mississippi State University, Mississippi State, Miss.
(Tags for translation) Ink spot grass