Spring Dead Spot

Causal Agent: Leptosphaeria korrae

Susceptible Turfgrasses: Common couch grass, South African couch grass and their hybrids.

Symptoms

• Circular patches of bleached, straw coloured dead grass appear in Spring as the dormant grass resumes growth.

• Patches are also visible in Autumn and Winter after a series of unusually cool days or wet, cold weather.

• Patches are a few centimetres to 1m in diameter.

• Patches reappear and expand in the same spot for 3 or more years.

• After 2 to 3 years, the centres of active patches may remain alive, and the patch takes on a “ringlike” appearance.

• Rings that coalesce can appear as serpentine arcs.

• Roots of affected plants turn dark brown to black and are severely rotted.

• Regrowth of grass into affected patches is slow and patches may remain barren of fill with weeds.

• When the grass recolonises an affected area it remains stunted.

Conditions Favouring Disease

• Most active when temperatures are cool (12 to 14°C) and soil is moist.

• Roots of Couch grow most rapidly at 24 to 29°C and extremely slowly at 15°C, thus the fungus has a competitive advantage at low temperatures.

• Spring Dead Spot favours cool, wet weather in the spring and autumn and daily temperatures of less than 15°C.

• This disease is typically found where thatch is more than 1.2cm thick and in locations with poor drainage and low potassium levels.

• Heavy applications of nitrogen in late summer often increase disease severity the following spring.

• Spring Dead Spot is more severe on turf that is over three-years old and in locations with long dormancy and cold temperatures.

Click to Download