Ophiosphaerella korrae

Other common names:

Springy and SDS.

Description:

There are two species of Ophiosphaerella (formerly Leptosphaeria) that cause spring dead spot; but in Australia the dominant causal agent is Ophiosphaerella korrae (J. Walker & A.M. Sm. bis). Ophiosphaerella korrae also causes necrotic ring spot within turfgrass. It has been classed by turf managers and pathologists alike as one of, if not the most serious disease of Cynodon spp. in Australia.

Ophiosphaerella korrae is a member of the ectotrophic root-infecting fungal complex of soil-borne pathogens on turfgrass (Miller, 2007). Spring dead spot appears as circular patches of “bleached”, straw coloured dead grass, a few centimeters to 1 metre in diameter (commonly less than 50 cm) when turf resumes growth in spring. The patches may combine to form large areas. On affected plants dark elliptical sclerotia (a compact mass of hardened fungal mycelium) are often visible on stolons. Dark sunken lesions can be seen on affected crown buds, roots and stolons; these areas may become black, necrotic, and brittle in advanced stages of infection (Wong and Harivandi, 2009. Sometimes, the symptoms are not evident until 2-3 or more years after the establishment of the disease at which time the centres may remain alive and take on a “ring-like” appearance. Weeds are often found within the centre of the patches where competition is less severe to non-existent.

Cause:

Spring dead spot favors older turf which may have a high thatch level, low potassium level, poor drainage and reduced irrigation. Spring dead spot favors cooler conditions when couch growth has slowed or is dormant. Incidence of the disease may be elevated by high nitrogen applications. Spring dead spot can spread across your turf area by machinery, transfer of clippings, by water within the soil etc.

Symptoms: 

Expanding circular patches or spots appear often in spring within mature turf swards that are routinely managed e.g. sports fields, and golf courses. However, symptoms can also be seen in autumn and winter after cool climatic conditions and/or wet weather. Roots of affected plants turf dark brown to black and are severely rotted.

Distribution:

The disease is normally found on established turf across all states and territories within Australia and has low economic significance. The disease affects both warm- and cool-season turfgrasses.

Lifecycle: 

Ophiosphaerella korrae is thought to survive unfavorable environments as mycelial plaques in plant debris. The fungus is thought to move from plant to plant by growing ectotrophically along the surface of roots and rhizomes, and infecting cells in the root cortex (Miller, 2007). Patches are commonly seen in spring, hence the name spring dead spot. However, symptoms can also be seen in autumn and winter after cool climatic conditions and/or wet weather.

Susceptible Turf:

Spring dead spot is found within varieties of Cynodon spp. This includes Cynodon dactylon (green couch) and C. dactylon x C. transvaalensis (Cynodon hybrid). There are reports that spring dead spot has been found within other turf species including Agrostis palustris (creeping bentgrass), Festuca sp., Axonopus compressus (broadleaf carpetgrass), Stenotaphrum secundatum (buffalograss), Pennisetum clandestinum (kikuyu), Eremochloa sp., Poa annua (Poa), Poa pratensis (Kentucky bluegrass) and perennial ryegrass (Lolium perenne). However, the latter species, excluding Kentucky bluegrass (although newer cultivars have been bred for resistance to spring dead spot), are more tolerable to spring dead spot infection.

Environmental triggers: 

• Temperature: - Active when daily temperatures are between 12°C and 14°C when couch growth is inactive/semi-dormant.
• Humidity: - Low relative humidity. Spring dead spot usually favours a series of unusually cool days or cold weather.
• Rainfall/water presence: - Favors wet weather and moist soil conditions.

Control options:

• Pesticides:
  • See available tabs below for registered products. Use as per label instructions.
  • If the disease is common to your turf (known history), apply a preventative fungicide application during late summer and autumn to prevent or reduce the likelihood of SDS infection.
  • Chemical control measures (currently registered in Australia) include products with the following active ingredients: bitertanol, carbendazim, chlorothalonil, prochloraz, procymidone, propiconazole, thiram, thiram+quintozene, thiram+metiram, thiabendazole and triadimenol
• Integrated Pest Management (IPM):
  • Use a combination of approaches listed on this page.
• Cultural: 
  • A disease outbreak such as dollar spot might be triggered by late afternoon/early evening watering of the lawn. The excess moisture applied late afternoon/early evening using a sprinkler may not seem like a problem, however the moisture takes far longer to dry off the leaf surface at night and can result in favourable conditions for disease development.
  •  Maintain turf density and nutrition, especially nitrogen and potassium, to at least an acceptable standard.
  • Control weeds in affected patches to limit competition and enhance recovery
• Mechanical: 
  • Reduce thatch levels within the turf sward.
  • Improve drainage and airflow within the soil profile. Routine decompaction work will assist here.

Disclaimer:

Turf Finder or its developer accepts with no responsibility for any consequences whatsoever resulting from the use of any information or product(s) listed herein. Products are to be applied as per label instructions.