Grass Grub

Grass Grub Costelytra zealandica

The grass grub is found throughout New Zealand and is considered to be New Zealand's major pasture and lawn pest.

Eggs are laid in clusters in the soil during summer; normally hatching after about 2 weeks. The larvae then feed on the roots of grasses until spring. In spring the mature larvae burrow further down into the soil and construct cells in which they pupate. In October when the adults emerge from their pupae, massed flights of soft buzzing slow flying beetles often occur on still warm nights. Later congregating in huge numbers, they feed on fruit trees and shrubs which are often severely defoliated.

The grubs are usually found about 15cm below the surface and control of the grub requires getting insecticide to this level in the soil. Kiwicare NO Insects Lawngard Prills are formulated to slowly release soil insecticide deep into the soil with watering and rain; giving good control and protection of roots.

Other similar soil insect pests include:

Black Beetle Heteronuchus arator

The adults of this species can be found throughout the year but are more frequent March to October. The larvae grubs live in the top 5cm of the soil and eat the roots of grass plants. Often the first sign of damage is seen as areas of the lawn dying during dry weather conditions. The grubs are larger than grass grub (10 - 20mm) and are creamy white with a black head and abdomen. The adult beetles do little or no harm to the plants.

Porina Caterpillar

The porina caterpillar causes similar damage to the roots of lawn grass and pasture. The adult porina moth lays eggs on grass in spring. On hatching the caterpillars move to leaf bases where they feed. As they grow they burrow into the soil and emerge at night to feed on leaves. They do most damage in autumn and early winter. Porina is the more easily controlled pest and the treatment recommended below will control both pests.

More information on grass grub.....

How to get rid of Grass Grub, Black Beetle and Porina

1. Sprinkle NO Insects Lawngard Prills on the grass paddock and lawns you wish to protect for grass grub. Ideally use February-April but can be used effectively through to spring.
2. The prills must be watered in, so sprinkle before (heavy) rain or water the area thoroughly after treatment.

NO INSECTS LAWNGARD PRILLS

This product is specifically formulated to control ground and soil dwelling insects such as; ants, grass grubs, crickets, porina caterpillars, cluster flies, carrot rust fly, wire worms and slaters. Sprinkle granules over the problem areas, then water in well. The insecticide is carried into the soil where the grubs are feeding, or by direct contact of the porina caterpillar in their tunnels.

More information.....

Classroom Clips

• New Zealand native grass grub is called TUTAERURU.
• Adult body length is 10mm and is shiny light brown.
• Eggs are laid in batches of 10 - 40 (75 - 175mm below the soil surface). Moisture is required for development.
• A single female may lay as many as 50 eggs which are light in colour, oval in shape and can be seen by the naked eye.
• Under normal conditions egg to larvae grub stage takes 3 weeks.
• 4 to 5 weeks later the 2nd grub stage is reached. The 3rd grub stage takes a further 5 to 10 weeks, these 3rd stage grubs are usually found in the top 25mm of soil.
• Grubs finish feeding around July, August and move downwards into the soil to pupate.
• Pupae stage lasts 4 to 6 weeks after which the insect changes to the adult beetle to emerge again October to January.
• The complete metamorphosis cycle of the grass grub can be as short as 8 months or up to 2 years in some southern areas.
• The roots of many plants which are damaged by grass grub include: Grass, clovers, Strawberries, Raspberries, Flowering plants, roots of Pine seedlings and many other kinds of plants and vegetables.
• Foliage attacked by adult beetles include: Apple, Pear, Quince, Plum, Peach, Nectarine, Cherry, Apricot, Grape, Citrus, Strawberry, Turnip, Swede, Rape, Willow, Gooseberry, Hawthorn, Honeysuckle, Sycamore, Karaka, Boxthorn, Gorse, Barberry, Pines, Microamp, Broad beans, Silver beet, Rhubarb and many other plants.