Tony Dickerson and Terry Walton answer all your gardening questions
Tricia White, by email
Tony says: Red thread is a common fungal disease that causes brown patches to appear in the turf. The first sign is patches of grass, up to about 25cm (10in) in size, turning a slightly reddish hue which later become light brown in colour. When wet the characteristic pinkish-red, threadlike structures about 2mm in length can often be made out, as can small, pink, cottony fungal growth.
It’s especially common during wet summers and autumns and on light, relatively infertile soils. The fungus doesn't affect the roots so it rarely kills the turf off completely. Your lawn may actually start to recover after a few weeks, even without further action. However, you’ll need to take action where the disease is a persistent.
There's a fungicide available containing trifloxystrobin (sold as Bayer Lawn Disease Control). It can be applied at any time of year but avoid periods of drought or freezing weather. Apply it no more than twice a year to avoid fungal resistance building up and should be used as part of a programme of other control methods. Some lawn care contractors may also offer treatments based on professional fungicides not available to the home gardener. When mowing, collect
up grass cuttings and don't compost them but dispose to prevent further infection of other areas of the lawn.
Often, the application of nitrogen is sufficient to control red thread. This can be applied as sulphate of ammonia at 15g per sq m (½oz per sq yd) before the end of August. Later applications will encourage soft growth, which is more susceptible to other turf diseases over the winter.
Poorly-drained lawns may also be more susceptible to red thread. Lightly scarify to remove thatch. This is best carried out in spring or, better still, autumn. To increase aeration, use a fork inserted as far as possible every 5cm (2in) or so. Alternatively, hollow tine the lawn in autumn and top dress with a sandy mix.