Sphaerulina trifolii
SYMPTOMS
The initial symptom of the disease is yellowing of the leaf tips, the affected area turns from yellow to brown and spreads into the leaf sheath. The blades become necrotic and wither, leading to the death of large areas of grass. Small brown pseudothecia appear in the dead tissue. There are laboratory tests showing that Leptophaerulina spp. does not grow at temperatures higher than 25º C. Abler (2003). The end of summer is when the first symptoms appear, with mild autumn temperatures, high humidity, anaerobic soil, an unbalanced balance of nutrients and low mowing, all of these conditions can favour the appearance of the disease.
Ascospores of L. trifolii are similar to the morphology of L. macrospora ascospores isolated in China on Poa pratensis leaves on a golf course, but are distinguished by the slightly larger ascospore size of L. trifolii over L. macrospora.
A Large areas of dead plants, B Pseudothecia on the stem, C, D. Pseudotecio E. Asco with ascosporas, F Ascosporas.
Scale: C-F 20 µm,
DESCRIPTION
Pseudothecium dark brown, immersed, erumpent, 130-250 µm in diameter (n=30). Peridium composed of 2 layers of brown cells of angular texture, with a thick pore in the upper part of the pseudothecium. Asci bitunicate, thick-walled, sacciform, octosporic, (45-) 50-70 (-80) x (35-) 40-60 (-65) µm (n=40). Ascospores hyaline, irregularly placed in the ascus, dichthyosporous, oblong to cylindrical or ellipsoidal with 3 to 4 transverse and 1 to 2 longitudinal septa, (25-) 30-40 (-50) x (10-) 11- 17 (-20) µm (n=45). As they mature they may appear pigmented.
BIBLIOGRAPHY
Abler W. Steven. Ecology and Taxonomy of Leptosphaerulina spp. Associated with Turfgrasses in the United States. Doctoral Thesis (2003).
Junmin Liang, Guangshuo Li, Lingwei Hou, Meiqi Zhao & Lei Cai. Leptosphaerulina species isolated from golf turfgrass in China. With Description of L. macrospora, sp. Nov. Mycologia 113(5): 961 (2021).
Petrak, F. Beiträge zur Österreichischen Pilzflora. Sydowia 13(1-6): 76 (1959)
Leptosphaerulina Trifolii fungus
