Lawn Pests

Sod webworms are caterpillars of small brown to dull grey moths. Webworms grow to a length of nearly 3/4 inch and vary in color from pinkish white to yellowish brown with a light to dark brown or black head. They are covered with fine hairs. The moths have a wingspan of about 3/4 inch.
They fold their wings closely about their bodies when at rest and have a prominent forward projection on the head. Moths hide in shrubbery or other sheltered spots during the day. They fly over the grass in early evening. The female scatters eggs over the lawns as she flies.
Sod webworms feed at night. Damaged grass blades appear notched on sides and are chewed raggedly. Irregular brown spots are the first signs of damage. Large areas of grass may be damaged severely. A heavy infestation can destroy a lawn in only a few days. 

The grubs that you see in the lawn are the larvae of beetles and chafers. These grubs are C-shaped, off-white in color with a dark head. They eat the roots of grass, causing irregularly shaped patches of wilted, dead or dying grass in April and May, and again in August to mid-October. With a serious infestation, the turf can be lifted up from the soil and rolled back like a carpet.
Lawns that are heavily damaged by grubs will have a yellowish tinge and will feel spongy when walked on.
In small populations, grubs do not represent a problem to a healthy lawn. It is normal for all lawns to have some grubs present. 4-6 grubs per square foot of grass won’t cause any visible damage in a healthy lawn. However, when a lawn begins to have more than 6 grubs per square foot of lawn, this would be considered a grub problem.
To check the size of a grub population in your lawn, dig out a square foot of grass and turn it over to examine the roots. Count the visible grubs. If you have more than 6 visible grubs, you will need to apply our Insect deterrant.

Areas which have been a problem in the past and areas where there is light shining at night such as street lights, security lights or light from un-curtained windows, are places where the largest populations of grubs are likely to be found.
 

Porina are found throughout New Zealand and attack most pasture species including turf grass. Porina caterpillars damage grass in late autumn and throughout winter as growth slows. Caterpillars are greyish yellow with a dark brown head, and grow up to 6 cm in length. They live in tunnels in the soil, emerging at night to feed on the surface, grazing grass and clover.
Their tunnels are often surrounded with bare patches of grass and the tunnel entrances can be found as holes, covered in soil castings and debris held together with silken threads

Stem weevil is a pest of ryegrass throughout New Zealand. Populations can reach 500-1000 larvae per m², causing significant fine turf grass damage.
To find larvae, look for dead or dying central leaves in tillers, that when lightly pulled come straight out of the plant – due to being eaten at the base of the stem. Larval damage is usually seen when your lawn are growing slowly, and shouldn’t be confused with drought stress.
New lawns seem to be more susceptible than older, established areas.
 

The black beetle grubs are generally only found in the North Island and the further north you are the greater the problem. The adult beetle starts off as a rich chestnut colour, but soon after changes to a  glossy black. It is about 15 mm long, with the male usually slightly smaller than the female.
 

The damage done in lawns by black beetle is very similar as damage by grass grub,  severe infestations of either grub causes the lawn to brown off, and can be rolled back like a mat owing to the complete destruction of the root system by the larvae.  Black beetle outbreaks are worse with higher than average spring and summer temperatures.

All stages of this beetle live predominantly underground, so inspection is advised before spraying with an insect deterrant.