What to look for
Patches start with a reddish tinge, typically 7.5-25cm across, later turning light brown or almost bleached-looking. The giveaway is pinkish-red, gelatinous, thread-like structures visible on the affected grass leaves, easiest to spot close up or in early morning dew.
It's most common in late summer and autumn, and tends to flare up after wet spells, which fits Kent's weather pattern most years.
Why it happens
Red thread is caused by a fungus, Laetisaria fuciformis, and it develops on turf that's poorly aerated and short on nitrogen. Heavy rain washes nitrogen out of the soil, weakening the grass, which is exactly the condition the fungus takes advantage of.
What the RHS actually recommends
Feeding the affected area helps directly, the RHS's own figure is sulphate of ammonia at 15g per square metre. Beyond that, scarifying and aerating to improve drainage, keeping the lawn adequately fed with nitrogen generally, and avoiding composting the grass clippings from an affected lawn (so you're not spreading the fungus) are the main non-chemical steps.
There are no fungicides currently available to home gardeners for lawn disease control in the UK. Professional treatments exist but sit under separate legislation, they're not something you can just buy off a shelf.
The good news
Red thread doesn't affect the grass's root system, so recovery can happen naturally within a few days to a few weeks even without doing anything. Feeding and improving drainage speeds that up and reduces the chance it comes back, but a patch of red thread isn't the same as a lawn that's actually dying.
Lawn looking patchy?
We can take a look and tell you whether it's red thread, moss, or something else, across Sandwich, Deal and the villages.