Internationally Large Patch is a fungal disease caused by a specific strain of Rhizoctonia solani. It attacks warm season turf in autumn and spring just as it is going into, or emerging from, dormancy.
While both Large Patch and Brown Patch are caused by the same core pathogen species Rhizoctonia solani, the different strain behind Large Patch is recognised as a discrete disease in its own right.
What are the symptoms of Large Patch?
General symptoms of Large Patch include:
Small, reddish-brown or black lesions that develop into rings and patches ranging in diameter from 30cm to over 6 metres
These patches are reddish-brown to yellow with bronze-coloured edges
Patches have an expanding look to their edge and often look like multiple patches converging
Damaged leaves easily detach from stems when gently tugged
What pathogen causes Large Patch?
The Rhizoctonia solani strain AG 2-2LP pathogen is the causal agent shown to be behind large patch in many parts of the world. It can be found in soil, thatch and root zone tissues at most times throughout the year waiting for supportive environmental conditions to occur. Local testing in Australia has suggested an alternate strain may be involved here – but this remains unresolved.
When does Large Patch occur?
More commonly Large Patch will develop in autumn and can cause significant damage over a longer period even interfering with spring green up many months later if left unchecked.
The disease becomes most apparent during cool, wet weather, especially when soil temperatures dip below 21°C and humidity levels are high.
What turfgrasses are especially susceptible to Large Patch?
A range of warm season turfgrasses such as Couchgrass, Zoysia and Kikuyu are particularly susceptible to Large Patch. Here in Australia we have seen aggressive activity at times on Kikuyu in late summer into autumn.
What can I do to manage Large Patch?
Prevention is key, as Large Patch recurs yearly under the right conditions and can be challenging to manage once established.
To minimise the risk of Large Patch, undertake the following cultural practices:
Avoid applying excessive nitrogen before humid periods and minimise nitrogen applications in late summer to autumn
Avoid overwatering and improve soil drainage whenever possible
Reduce thatch buildup
Remove morning dew
Increase the height of cut
In areas prone to Large Patch, timely preventative fungicide applications are essential.
For chemical solutions or treatments for Large Patch, please see the recommended products below.
Velista is a powerful broad spectrum fungicide that can be used all year round and can be trusted to keep your turf in excellent condition especially when high temperatures and high humidity hit your facility.
Xzemplar™ is a turf fungicide offering advanced systemic movement of the active ingredient, Fluxapyroxad. Xzemplar combines a quick knockdown and powerful, long lasting control.
Headway Maxx combines the strength, longevity and broad spectrum of Heritage Maxx with the speed and early curative action of Banner Maxx in an unbeatable combination.
Dedicate FORTE Stressgard® is a broad-spectrum DMI fungicide containing tebuconazole (240 g/L) with Stressgard Formulation Technology, and controls tough soil-borne and foliar fungal diseases in both cool and warm season turfgrass.
Dedicate turf fungicide contains two active ingredients with two different modes of action, providing curative and preventative control. It has a contact and systemic action in turf which provides broad spectrum control.
