thisplace.com.au - Lawn Grubs - Mother Nature's Curse to the Gardener

» Have you wondered why your lovely green lawn suddenly goes brown and straw like?

» Are there moths and wasp like insects flying over your lawn?

» Maybe the leaves on the grass runners are just disappearing?

Then Maybe You Have Lawngrubs ...

What are lawn grubs?

Lawn grubs are simply leaf eating caterpillars. There are 3 main types you may encounter which are:

Armyworm: These caterpillars are dark green, smooth and hairless, 25 to 300mm long with distinctive stripes along the sides of their body, feeding at night through the growing season. From 1 to 6 generations may occur in the course of a normal growing season. They feed voraciously on the grass blades attacking on various fronts like soldiers (hence the name Armyworm) and sometimes devastating the entire lawn.
Sod Webworm: This particular grub is greyish to tan in colour, about 20mm long and spotted, also feeding at night through the warmer months. From 2 to 5 generations may occur throughout the growing season. The adult moth drops her eggs at random during the night, eggs hatch in one week. Usually chewing off leaves near the base of the sheath.
Cutworms: Thick bodied caterpillars with a length of 38 to 50mm. These caterpillars are greenish grey, brown or black often with spots or stripes. Feeding at night through the growing season with 1 generation per season for most species and 2 to 4 for others. They can chew the grass shoots down to the surface but are normally considered a minor problem.

Where do these grubs (caterpillars) come from?

All grubs are larvae of an adult moth. Moths will lay there eggs in different ways , whether in flight by the sod webworm adult moth to the army worm adult moth which lays her eggs on leaves and eaves at night and cover with a light greyish fuzz.

When do they appear?

Normally mid summer and early autumn. They are a seasonal problem where the moths lay their eggs throughout the warmer months. The intensity and time of first appearance can be greatly influenced by how cold our winters have been.

How do we know they are here?

There are several quick ways for early detection.

Circular to irregular patches of your lawn dying or thinning.
Place a wet hessian bag on your lawn overnight, the grubs present will be visible when you lift the bag in the morning.
An accumulation of small green pellets of excrement (appear like balls of grass mulch) found within the thatch or damaged area.
A reddish-purple wasp type insect hovering around the surface of your lawn. These wasps are often mistaken as the cause of lawn grub but in fact they are actively seeking out the lawn grub so they can inject the caterpillar with its own eggs, using the grub as a host.

How do I fix this problem?

The only way is to spray an insecticide.

Lawn grub killers are easily obtainable from Hardwares, Supermarkets and Nurseries. The containers come in many different applications, from Hose and Spray types to concentrates.

A friendly alternative to spraying may be to encourage birds to your area by simply throwing bread crumbs on the ground to attract the birds, who in turn will eat the Lawn Grub. This method is by no means a positive way of treatment.

How often do I have to treat my lawn?

Just because you have eliminated an infestation does not they will not reappear. This is due to the fact that you have only eliminated the moths larvae, not the moth, who can lay many more generations. Therefore, treat when the problem appears.

Can I help repair my damaged grass?

Yes, after treating for lawn grub, a simple application of fertiliser will help shoot and leaf growth. Then continue to water and mow as normal. Apply fertiliser as per manufacturer's recommendations.

Source: The Jimboomba Turf Group