What are Army Grubs?
Army grubs are from the moth family. These grubs take 21-35 days to mature and can be 3-4 centimetres in length. An army grub has stripes or triangular patterns along its smooth body. This differentiates them from the Sob Webworms that are less harmful to turf. After another 10-14 days the grub will become a moth. Army grubs are not good for lawns as they cause severe damage, which is exacerbated by the fact they move in large groups, hence the name Army.
Signs of an Invasion
Unfortunately army grubs like healthy and well looked after lawns as a place to start their reproduction cycle. Some common signs that you have an infestation are patches of brown, dry or brittle turf interspersed with healthy green grass. This patch will tend to spread across lawns methodically as the grubs eat the grass.
To check you have in infestation you can do three things.
- Pour some soapy water over the damaged area. Wait ten minutes to see if any caterpillars emerge. If there are a lot then you have a problem.
- Go out to the lawn at night with a torch and look for caterpillars in the damaged turf. Look to the outer healthy grass, as that’s where they will be eating.
- Leave an outside light on at night. If there is more than the usual amount of moths then you could have an invasion.
How to protect your lawn
If you are sure you have an invasion, or even just concern, it is easy to treat your lawn to get rid of the army grubs. You can easily buy lawn insecticide from garden stories and lawn specialists.
It is best to use the insecticide just before dusk. You should treat the entire lawn area, and then lightly water the grass so the insecticide soaks into the soil and is ingested by the army grubs. Repeat the treatment again during the warmer months as the life cycle of the moth is quite short and they can re-infest the same area.
If you have any concerns about army grubs or the quality of your Sir Walter turf then treating your lawn with insecticide during summer can be a good idea to keep your lawn in top shape.