Repairing lawn damage

Renovation of neglected lawns

A renovation programme involves a series of procedures that restores the lawn to a good condition. In early spring, cut the turf to 5 cm and remove the clippings. Reduce the cutting height incrementally at subsequent mowings until the required height is reached. Then, fertilise the lawn, and apply a herbicide two weeks later to control weeds. Reseed bare or uneven patches one to two weeks after herbicide application. At the beginning of autumn, aerate, top-dress with sand-soil mix, and fertilise the lawn, in that order of events. Follow a regular maintenance programme thereafter (see Table 1).

Damaged edges

Edges that have been damaged in small areas can be repaired by cutting the turf with an edger against a plank of wood. Slice under the section of turf with a spade (Figure 1) and slide it towards the lawn edge until the damaged area is outside the lawn. Trim off the damaged part to align the turf with the existing lawn edge. Re-grass the resulting gap in the turf within the lawn by adding a little soil and reseeding with a grass mixture.

Figure 1: Repairing a damaged edge.

to top of page

Levelling a hump or hollow

Cut a cross through the turf on an affected area, and peel back the cut turf (Figure 2). To level a hollow, fork over the soil beneath and fill in with topsoil, and firm the ground. For a hump, remove the excess soil until the ground is level, fold back the cut turf and tamp it down with the back of a rake, before top-dressing and watering.

Figure 2: Levelling in a hollow or hump.

Annual maintenance programme

The annual maintenance programme is summarised in Table 1.

Table 1: Annual maintenance programme.

to top of page

Diseases

Turf diseases in hot humid regions include brown patch, dollar spot, fairy rings, Fusarium patch and red thread. Fusarium patch may also occur in cold regions, even under frost or snow. Other disease-like problems occur in waterlogged areas.

Algae and lichens

Algae and lichens may be prominent, particularly in poorly drained and aerated or compacted soils. Patches of green to greenish-black, slimy, slippery algae and gelatinous lichens, or dog lichens, which are recognised by groups of curled leafy growths that are greenish-black on the upper surface and creamy-white on the lower surface, can be controlled by removing the thatch, aerating the lawn, and/or installing drainage pipes. Trees or shrubs that provide excessive shade over the lawn should be trimmed as well.

to top of page

Dollar spot

Dollar spot is a common fungal disease of turf grasses throughout the growing season. There are at least two strains of the dollar spot fungus in the genera Moellerodiscus or Lanzia that cause disease during cool and warm seasons. The fungus initially appears as a 3-8 cm circular to irregular straw-coloured patches that eventually darken and coalesce to form larger blighted areas. Individual blades typically have straw-coloured or bleached white lesions across the blade width, which causes the blade to be pinched in the middle and gives the appearance of an hourglass-shaped lesion. The lesions are also commonly bordered above and below by dark brown bands and the blades also show dieback from the tip. When the fungus is active and moisture is present during the early morning hours a cobwebby growth can sometimes be seen growing on the grass blades.

The disease affects most turfgrasses, but turf containing fine-leaves bents and creeping fescues are susceptible, while tall fescue appears resistant. Turfgrasses grown under low fertility conditions appear to be the most susceptible to dollar spot. Drought also increases susceptibility to disease along with thick thatch and compacted soil. Favourable conditions for disease development include warm humid weather and cool nights with heavy dew formation.

The fungus favours heavy or compacted soils with a high pH, such as alkaline soils or those treated with alime. It appears in mild damp weather.

An application of nitrogen fertiliser at the 3 g nitrogen/m² will stimulate foliar growth at a rate faster than the fungus can injure the blades. Lessen the severity of the disease by alleviating drought stress with regular watering, and avoid thatch build-up and compaction of the soil. Over-seed with resistant cultivars from the recommended turf grass cultivar lists. Improve soil aeration and remove thatch. Reduce soil pH with sulfur or acidic fertilisers such as ammonium sulfate. Apply cyproconazole, chlorothalonil or iprodione (Table 5).

to top of page

Slime moulds

Slime moulds are recognised by clusters of beige, orange or white fruiting bodies that smother individual blades of grass. The spores that are released give the slime mould a grey appearance. The grass looks unsightly but is not harmed. The condition is particularly common in late spring and again in early autumn, when rainfall is high. The slime can be washed of the grass using a high-pressure hose directed onto the affected areas.

Snow mould/Fusarium patch

Lawns that contain a high proportion of annual meadow grass (Poa annua) are particularly susceptible. Patches of grass become yellow and die, often coalescing to form large areas. In autumn when conditions are damp and night temperatures are low, a white fungal growth appears, causing the grass blades to stick together, giving affected areas a slimy look. Control options include regularly aerating and scarifying the turf. Avoid using high-nitrogen fertilisers in late summer to early autumn. Treat affected turf with chlorothalonil or iprodione (Table 2).

to top of page

Red thread

Fine-grassed lawns are particularly affected by red thread. Very small, pale-pink to red gelatinous, branching threads of fungus develop on small patches of grass, which later become bleached of colour. The fungus very rarely kills the lawn. The fungus is common after heavy rain, and when the soil is nitrogen deficient or poorly aerated. Aerating, scarifying and fertilising the turf will control the disease. Chemical control should not be necessary on a well-maintained lawn. However, if the infestation is severe, apply cyproconazole, chlorothalonil or iprodione for effective control.

Toadstools

Toadstools are fungal fruiting bodies that sometimes develop in distinct circles (‘fairy rings’), often on buried woody material. Most cause little damage to turf, but fairy rings are harmful and disfiguring to it. Two circles of very lush, green grass form, one within the other, and may be 2-5 m in diameter. The grass in between the circles dies, killed by toxins released by the fungal mycelia between the rings. Toadstools then emerge on the outer part of this middle zone. A white, fungal growth permeates the soil in the area of the ring. The fungi are spread to new sites by wind-borne spores.

Control consists of brushing off the toadstools when they first appear, before their spores are produced. Remove any fungi on buried wood. The fairy rings cannot be controlled using fungicides, although watering with a wetting agent may make the soil less susceptible to fungal growths.

to top of page

Integrated controls for turf ryegrass

Perennial ryegrass is not affected by autumn Fusarium patch disease, which badly affects browntop. Ryegrass can be affected by red thread disease from autumn to spring, particularly in sheltered and shaded positions. Crown rust can also affect certain varieties, but most appear to be resistant to it now. For both diseases an application of nitrogen fertiliser once temperatures are above 10°C is usually a cure.

Table 2: Fungicides registered in 2003 for control of diseases in cotula, dichondra, fine turf, greens and lawn turfs.

to top of page

Acknowledgements

Thanks to Bill Walmsley, New Zealand Sports Turf Institute, for his article which was abridged for the section ‘Perennial Ryegrass for Lawns and Turf’, and Sam Wakelin for the drawings in Figure 1, Figure 2 and 3. Thanks also to Robert Lamberts for the photographs of weeds.

to top of page