Diseases

brownpatch crownrust dollarspot fairyrings
Brownpatch Crownrust Dollarspot Fairy Rings
fusarium leafspot redthread slimemoulds
Fusarium Leaf Spot Red Thread Slime Moulds
yellowtuft
Yellow Tuft




Brownpatch

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This is a relatively common disease whose causal agent is Rhizoctonia spp. and it can affect all turfgrass species during the summer months. The favourable conditions for its occurrence are warm humid weather patterns, particularly when soils are poorly drained and the sward is heavily thatched. It is more commonly observed on browntop or fine fescue rather than ryegrass. This disease shows as rapidly enlarging irregular or circular patches where the foliage turns purplish initially followed by a light brown colouration. Occasionally the turf will recover in the centre of the effected area and this will result in the appearance of a ring of diseased turf.


Solution
  • Prevention is best effected by applying a systemic fungicide.
  • De-thatch the lawn in autumn to assist prevention and address any drainage issues.



Crownrust

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The causal agent for Crown Rust is Puccinia coronata. and it affects both ryegrass and Kentucky Bluegrass. It can occur at any time of the year but tends to be most common from early summer to late autumn particularly in mild, humid weather conditions. The affected turf appears rust coloured due to the production of numerous yellow or orange spores on the leaf.

Often these spores can be easily detected on footwear when walking across an infected lawn.


Solution

Apply a nitrogen rich fertiliser such as NitraKing at 35gms/m2 or 3.5kgs per 100m2. Ensure that this fertilizer is applied prior to impending rain, during rain or alternatively water the lawn thoroughly after application.Increase the water application after application.Mow more frequently




Dollarspot

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The causal agent for Dollar Spot is Sclerotinia homoeocarpa and all turf grass species can be affected. The favourable conditions for this disease which is a common occurrence in the top half of the North Island are when the plant leaves are wet for extended periods of time particularly from mid-spring until autumn. The symptoms are numerous small bleached spots which may coalesce to form large irregular patches. These spots may vary is size from the size of a 50c coin up to 50mm. Recovery is usually rapid as the roots are not affected.


Solution

In the first instance apply a nitrogenous fertilizer such as NitraKing at 35gms/m2 or 3.5kgs per 100m2. Ensure that this fertilizer is applied prior to impending rain, during rain or alternatively water the lawn thoroughly after application.If conditions persist then a fungicide application may be required but this would be rare.




Fairy Rings

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The causal agent of this relatively common disease is Basidiomycete species. This disease is obvious by the rings, circles or arcs of stimulated turf growth. Occasionally these will be accompanied by the appearance of mushrooms. It is most commonly observed on sandy soil types and older, established and thatched lawns. In occurs more often in summer particularly when the fertilizer regime is either poor or non existent and presence of large amounts of decomposing organic matter.


Solution

Apply a balanced fertilizer such as Turf Gold applied at 35mgs/m2 or 3.5kgs per 100m2 Increase watering frequency. De-thatch the lawn in autumn.




Fusarium

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The causal agent is Microdochium nivale and most cool season grasses can be affected, particularly during periods of cool humid weather in late autumn. It is seen as very rapidly developing circular patches of 25-50mm in size and the leaves become brown and mushy. Tan blotches are first observed on the tips of leaves. It is more prevalent in established lawns carrying large amounts of thatch.


Solution

The formation of this disease is discouraged by high levels of sulphate and potash as well as acidic conditions. A balanced fertilizer regime such as regular applications of Turf Gold fertilizer therefore is generally effective against the establishment of Fusarium.Apply this product every 10 -12 weeks at 25gms/m2 or 2.5kgs per 100m2.De-thatch the lawn in autumn




Leaf Spot

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The causal agent for Leafspot is Drechslera & Curvularia spp. and it can affect all turfgrass species. Turf when close mown is more susceptible particularly during drought conditions. It is seen as browning of the leaf and general thinning of the sward.


Solution

Apply a fungicide at label rates.




Red Thread (Pink Patch)

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The causal agent for red thread or pink patch is Laetisaria fuciformis and Limonomyces spp. It is generally noticed as brown patches appearing in the lawn. Closer inspection particularly at the outer edges of these brown areas will reveal the characteristic red threads of mycelium growth. This is the most common disease exhibited on lawns comprised particularly of ryegrass or fine fescue, however, it can affect all other turf species. It is primarily a function of nitrogen deficiency and can occur at any time of the year, but tends to be more common from autumn until spring when consistently moist leaf blades provide ideal conditions for its propagation. It can be very site specific particularly in areas that are well sheltered or shady. Red thread can be prevalent on new sites particularly when the topsoil has been removed and replaced. The base saturation fertility level on these soils is low and as a result the plants struggle to uptake sufficient nitrogen to meet their requirements. It can take some time to build this fertility back to desirable levels. Therefore, during this period of time a regular balanced fertilizer regime is recommended.


Solution

  • Apply a nitrogen fertilizer such as NitaKing at 40gms/m2 or 4.0kgs per 100m2. Follow up with an application of Turf Gold in 3 weeks time at a rate of 35gms/m2 or 3.5kgs per 100m2. Thereafter continue applications every 8 -10 weeks until the problem abates. As the soil fertility increases the likelihood of a red thread outbreak will decrease, however, this may take some time to occur particularly on sandy soils or soils containing low levels of organic matter. Ensure that mower blades are sharp to provide a clean cut to the leaf blades, because leaf exudates formed at mowing wounds form favourable media for spore germination and mycelial growth.
  • Restrict foot traffic on the lawn until symptoms desist.
  • If irrigating or watering the lawn ensure that this occurs in the morning rather than the evenings.
  • If conditions persist then a fungicide at label rates. This should generally take place as two applications 14 days apart. Thereafter continue with the regular nitrogenous fertilizer applications.




Slime Moulds

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The causal agents for this disease include many Basidomcete spp. It is generally seen in winter when cool and wet conditions promote the formation of fruiting bodies. The fruiting bodies can of various colours but are most commonly grey purplish-brown or white. They are easily rubbed off by finger.


Solution

This is generally only a temporary condition and symptoms quickly disappear in dry weather.




Yellow Tuft

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The causal agent for yellow tuft is shlerophthora macrospore and it can affect all turfgrass species. Individual plants form into a dense turf of yellow leaves resulting in a bumpy surface. Yellow turfs are easily confused with poa annua but can be distinguished by the tight proliferation of leaves together with a weakened root system which enables the tufts to be easily pulled out.


Solution

  • Address drainage issues
  • Reduce the rate of water application.