Broadly, lawn brown patches can be split into three categories - depending upon the size of the patch. Recognising the size and shape of the patch - simple you might think - can go a long way in identifying the cause of the brown patch. I have had mails in the past where the write has claimed to have brown patches on the lawn, when in fact the entire lawn was brown - killed off by the wrong use of a certain weedkiller!
The time of year the patches appear can also be a clue in identification, mainly by means of eliminating certain causes. For instance, small brown patches in the late autumn or winter lawn would rule out root damage by leatherjackets. These tend to feed during the summer months!
Together with this, knowing the age of the lawn can also be a help in determining the cause. Lawns less than a year old, sometimes have medium to large brown patches as a result of mower damage on an uneven lawn.
Small regular spots - rather then patches -
Possibly caused by Dollar Spot Disease, of which there are several fungi causes. Named after its size - a dollar. But, if not noticed soon enough, can spread and form patches rather than just spots. Normally on fine well mown sports turf. Particularly noticeable in early spring or late summer. Rarely in hot dry weather. The affected grass is straw-coloured. Early morning dew will show as a fine web across the spot.
Medium Round patches - about 6-12in (150-300mm)
Large Circular Brown Patches
Large Uneven Patches
Irregular Patches over the lawn -
Scalping with Lawn Mower
Lady Dogs - bitches are a common cause of brown patches on lawns -
especially in hot dry weather. The light brown patches are roughly
circular and about 20 - 30 cms across. There is no remedy for this,
other than to keep your bitch off the lawn.
Where patching has occurred, then water the area well, to help soak in the urine. The grass sometimes recovers, but will normally require patching with turf or re-seeding. Water the urine out of the area first.
Scalping with the Mower Brown patches - Bare areas
If the brown patches are more like bare soil, then you are probably ‘scalping’ it with a poorly adjusted lawn mower ( you are simply scalping the humps off an uneven lawn.) Raise the height of the mower blades in the short term - we all cut grass too short anyway - and top dress the hollows with fine soil. Top Dressing lawns - or maybe you have an uneven lawn full of bumps.
If they are small brown patches of a few cms across, it could be the larvae of the Daddy Longlegs Crane Fly. The grubs - known as ‘Leather jackets’ - eat away at the grass roots until they are ready to surface in the late summer as Crane Flies. It is difficult to realize that the chunky grubs, turn into the slender bodies of the adult flies. I wonder what the secret is!
The chemicals that work, are not available ! So, you can water the lawn in the evening, cover the area with a plastic sheet, remove it the following day, and sweep off the offending grubs, which will now be on the surface.
Here's an Email response we got by trying this !!!!
(One added thought.. I assume that you have not applied a lawn feed/weedkiller too generously or without due care! If you have overlapped with the spreader, or applied unevenly by hand, then dark green stripes or patches may appear. They may also be scorched brown. Water the area generously, and all should be well within a few weeks.
Another common fault with applications of lawn feed, is applying them when the lawn is scorched dry, or even in mid summer in a dry period. Far better to wait until after a shower of natural water - rain. It nearly always waters the lawn better than we can!
If using a combined lawn feed/weedkiller, then other than the problem of possible scorch - see above - don't forget that the weedkiller element will (should) kill off any patches of weeds that were in the lawn prior to application. This will result in brown patches. Obvious to most, but come and read my help email box!
There are weedkillers that kill everything, there are weed killers that are a bit selective, and there are weed killer that kill grass! It is important to choose the right one!
Weed killing chemicals that are used in 'Lawn Weed and Feed' mixtures, or sold in liquid form as 'Lawn Weedkillers' together with some moss killers, are all formulated to specifically kill broad leaved plants. They are clever enough to know that they should not kill lawn grasses. Sometimes they are referred to as 'selective' weed killers. These types of weed killers are normally alright to use on lawns - if used properly, and of course after application, they will leave brown patches where they have killed the weeds in the lawn.
There are other types of weed killers, that do not give a hoot as to what they kill. These are NOT Lawn Weed Killers. Spray it and kill it is the motto! Typically this type of weedkiller contains Paraquat and Glyphosate. There are several others. Basically they will kill all plant growth they come into contact with.
We get several mails each year about brown patches on the lawn, which when we investigate, have been caused by the use of a general weedkiller, with the lawn owner thinking that they only killed weeds and not grass as well.