Sod webworms are a small green and brown caterpillar which feeds on the leaf blades of lawns, and will affect all lawn types. When fully grown, the sod webworm will reach a length of about 2 cm, will develop grey hairs over it's body which will eventually turn a tan colour, while it's head will often become orange.
Sod webworm will only feed at night during the growing season of lawns which is between Spring, through Summer and onto Autumn. Sod webworm will then hide in silk lined burrows during the daylight, helping them to avoid detection by people, escape the heat of the day, and to avoid being eaten by birds. Their burrows are usually located at the base of the lawn, usually at soil level or inside the lower thatch layer.
Sod Webworm are the caterpillar stage of the Crambus moth (aka - Snout Moth), which can often be seen flying over lawns at the end of the day. The Crambus lawn moth is an off-white colour, is usually between 2-3 cm long, and will be most easily identified by it's zig-zagging flying pattern very low over the lawn's surface. As the moth flies over the lawn, it will intermittently drop new eggs into the lawn thatch, which will hatch into new caterpillars 6-10 days later.
The damage caused by sod webworms will be seen as small spots of damaged turf which will eventually become larger, with a brown or yellow colour to the affected area. When numbers of these lawn pests begin getting out of control - the damage becomes far more noticeable across the entire lawn's surface.
Sod webworm will hide during the day and only come out at night, so detecting sod webworm can be a slightly tricky process, but it can still be rather simple thing to do with a little insight into their habits.
The lawn can be closely checked around any damaged areas early in the morning, and preferably if dew is still present on the lawn. Any signs of silken webs over the lawn surface will indicate an infestation of a lawn pest. Around this same area, pull the grass and thatch layer apart with hands and search for little silken tunnels in the thatch and near the soil surface. If found, this is a sure sign of Sod Webworm.
Further investigation can be undertaken at dusk, looking for little moths flying over the lawn in their familiar zig-zag patterns. An outdoor light will also attract these same moths at night.
The final method of detection is to catch the Sod Webworm in the act of eating our beautiful lawns. Once darkness has completely fallen, go out onto the lawn with a good bright torch, while down on hands and knees - check the lawn leaf and in-between the lawn leaf with the torch. If the lawn has sod webworm then this is the way to find them, making sure to always start the search inside and around the affected areas.
Sod Webworm is easily killed by an application of pesticide which can be purchased from most gardening shops. The pesticide is applied just before nightfall and watered into the thatch layer before the sun sets.
Applications of pesticide to kill Sod Webworm may need to be repeated several times as each new infestation becomes evident. This is because the Crambus lawn moth can continue to lay several generations of eggs over a season, there can also be unhatched eggs in the soil at the time of application, or moths and webworms in the lawns of neighbours.