Grass grub are the larvae of the Tutaeruru beetle Costelytra zealandica. The grass grub is found throughout New Zealand and is considered to be New Zealand’s major pasture and lawn pest. The cost to New Zealand’s agricultural industry is estimated at $90 million a year in lost revenue.
Grub Damage from Summer to Spring
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 and other plants until spring. The roots of many plants which are damaged by grass grub include: grass, clovers, strawberries, raspberries, flowering plants, pine seedlings, vegetables and many other kinds of plants.
Spring Adults Emerge and Feed on Foliage
In spring the mature larvae burrow further down into the soil and construct cells in which they pupate. In October to December, when the adults emerge from their pupae, massed flights of soft buzzing slow flying shiny, light brown, 10mm long beetles often occur on still warm nights. Later congregating in huge numbers, they feed on fruit trees and shrubs which are often severely defoliated. 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, barberry, pines, microamp, broad beans, Ssilver beet, rhubarb and many other plants.
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 a more easily controlled pest than grass grub and the treatment recommended below will control both.
Getting Rid Of Grubs or Larvae in Soil
The grubs are usually found about 15cm below the surface and control of the grub requires getting insecticide to this level in the soil. Slow release diazinon insecticide granules such as Kiwicare NO Insects Lawngard Prills are formulated to slowly release soil insecticide deep into the soil with watering and rain; giving good control of insect pests and protection of roots.
Sprinkle NO Insects Lawngard Prills or similar on the grass paddock and lawns you wish to protect from grass grub and porina. Ideally use February-April but it can be used effectively through to spring. This product is specifically formulated to control ground and soil dwelling insects such as; grass grubs, ants, 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. The prills must be watered in, so sprinkle before (heavy) rain or water the area thoroughly after treatment.
Getting Rid of Adult Beetles
To prevent the adult beetles damaging the foliage of your plants and vegetables and to reduce the likelihood of grub damage later in the year, spray plants with surface foliage insecticide such as Carbaryl 80.
Kiwicare is New Zealand’s own manufacturer and distributor of pest control, garden care and home maintenance products. The Kiwicare website contains advice on the eradication and prevention of all sorts of pests that bother us in New Zealand. Learn how to get rid of rats and mice, flies, spiders, ants, cockroaches, fleas, bed bugs and other creepy crawlies. Protect your plants from aphids, grass grub, caterpillars, weeds and more. Keep biting insects at bay with the Safari range of insect repellents. See the BioGro certified organic range of products to help you stay pest free without chemicals.How To Protect Your Lawn from Grass Grub,
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