Red Thread
Red thread is patches of dead grass on lawns which happens during wet summers and in autumn. It is caused by the fungus Laetisaria fuciformis. Red thread will rarely kill the grass completely, and the patches will recover with appropriate remedial action.
It is caused by a fungus that lives in your turf. All turf has this fungus in it. Normally you do not see the fungus or the disease it causes, but during conditions of high humidity & dampness, it may appear. Red thread is more serious on turf that is not being cared for. It can kill patches of your turf if it is allowed to develop for weeks at a time. It attacks all of the grass species grown for turf in the U.K.
The Chafer Grub - Phyllopertha horticola
Chafer grubs are soil-dwelling larvae of various chafer beetles. They feed on plant roots, especially those of grasses. Of the 5 species living in the British Isles the Garden Chafer is the most common.
Chafer grubs eat the roots of grasses and other plants. Evidence of their activities can be seen in a number of ways such as damage to lawns is most obvious between autumn and spring when the grubs are reaching maturity. Patches of the lawn may become yellowish and even start to roll up.
Birds, particularly of the crow family feed on the grubs, tearing up the loosened turf in the process. Damaging infestations can be highly localised and sporadic Chafer grubs can be found in the soil under the loose turf.
Fairy Rings
Fairy rings are symptoms of fungus in the soil. They show up as large rings of grass that are darker green than the rest of the lawn. The fungus feeds on decaying matter in the soil, releasing nitrogen that greens the grass. Fairy rings interrupt the manicured look of an evenly green expanse of lawn and indicate a wet and fungal condition that may get out of control. They are commonly accompanied by mushrooms and puffballs, fruit of the fungus, further adding to the odd look of the turf.
Fairy rings in lawns are visible but can be caused by different fungus conditions. If left alone, fairy rings will resolve when the organic matter the fungus is feeding on is totally consumed, which may take years. The right fungicide and fertilizer treatments resolve fairy rings much faster and may prevent turf die-off.
Leather jackets
Leather jackets can be damaging lawn pests by eating the roots and stem bases. They are often more numerous after a wet autumn, as damp conditions favour survival of the eggs and young larvae.
Lawns develop patches where the grasses turn yellowish brown and die. This can be distinguished from similar effects caused by lawn diseases or adverse growing conditions by lifting the affected turf and finding leatherjackets in the surface layers of the soil.