These are many reasons why these may occur and the most likely are not usually due to pests or diseases. The most common causes are:

• Petrol spills or leaks from the mower
• Uneven application of weed killer
• Uneven application of fertiliser
• Inadequate preparation before sowing grass seed may mean there is buried debris or an uneven surface
• Badly laid turf or uneven surface
• Uneven surface is ‘scalped’ while mowing
• Waterlogging/Bad DrainageDrought
• Excessive thatch
• Overuse
• Bitch marks (Dog Urine)

Diseases

• Newly sown grass: seedling blights, similar to ‘damping off’.
• Established lawns:Fusarium patch or snow moulds are prevalent in cold weather.Brown and yellow patch, take-all patch and red thread are prevalent when conditions are warm.
• Leaf spots and other fungi may also cause dead patches.

Pests

• Chafer grubs cause problems between autumn and spring. These fat C-shaped grubs are creamy white with brown heads.
• Leatherjackets (grubs of the crane fly) are at their most damaging in midsummer.