Lawn Care Advice – Diseases

Rust (Puccinia spp)

Symptoms:           
  • Early symptoms of Rust diseases appear as light-yellow flecks on leaves or stems
  • The flecks enlarge, elongate, and turn yellow in colour.
  • The yellowed area of the infected spots enlarge and elongate parallel to the leaf or stem axis as the infection matures.
  • The leaf blade turns yellow starting at the tip and progressing to the base.
  • The infected areas rise above the epidermis and then rupture, releasing spores that are yellowish-orange to reddish-brown in colour.
  • A severe disease infection can cause the shoot to turn yellowish to reddish-brown in colour and slow in growth.
  • As individual plants die, the turf thins.
  Conditions Favouring Disease:
  • Rust diseases typically occur in early spring through mid-summer
  • Rusts favour moist, low-light areas.
  • Leaf wetness is required for fungal growth
  • Depending on the species, rusts favour temperatures between 18°C and 30°C.
  • Severe rust infections occur on slow-growing turfgrass particularly those with low nitrogen levels and/or plant water stress.

Helminthosporium Complex (Dreschslera spp., Bipolaris spp. Excerohilum spp.)

Situation:

Predominantly golf and bowling greens of all species. Also effects kikuyu racetracks.

Turf Damage:

Causes reddish brown to pupils-black spots on leaves and stems which spreads quickly. Leads to turf desiccation.

Occurrence:

Wet conditions with high humidity between 3-30C.

Spring Dead Spot (Leptosphaeria spp.)

Situation:

Predominantly couch grass turf areas.

Turf Damage:

Circular patches often appear in autumn and at spring green up. Restricts growth in spring.

Occurrence:

Generates with soil temperature around 15C in dormant couch grass.

Pythium Blight (Pythium spp.)

Situation:

Predominantly golf and bowling greens affecting all turf grass species.

Turf Damage:

Begins as circular spots with a light brown water soaked appearance. Can feel slimy and effect large areas of turf quickly.

Occurrence:

Warm nights (+20C) and warm days especially with soft growth from nitrogen (N) application.

Brown Patch (Rhizoctonia solani)

Situation:

Predominantly golf and bowling greens affecting all turf grass species

Turf Damage:

First sign is a “smoke ring”. Plant leaves then appear “water soaked” before turning dark brown in patches up to 1m in size.

Occurrence:

Occurs at 15-20C with high humidity predominantly in spring and autumn.

Dollar Spot (Sclerotinia homeocarpa)

Situation:

Predominantly golf and bowling greens affecting all turf grass species.

Turf Damage:

Small (4-5cm) circular sunken patches.

Occurrence:

First appears as mycelium (cottony thread). Generally occurs at 15 - 30C with high humidity or dew, and low nitrogen levels in turf.