Curl grubs (often mistaken as witchety grubs) are the larvae of various beetles including Black beetles and the Christmas beetles commonly found in Australia. The larvae feed on organic soil matter and soil roots. Larvae are most active during mid spring to mid summer and can cause severe damage to lawns, gardens and potted plants.
Curl grubs have a creamy white body and a light brown head. They vary in size from 4mm to 40mm depending on age. The tail end of the grub may look dark brown as a result of the soil ingested during feeding. They curl up when disturbed.
Start monitoring for grubs and adult beetles from early spring and continue through to late summer. This is when adult beetles are most active. Note that the beetles are attracted to light and dry soil, so avoid garden lighting and keep plants well watered.
ORGANIC: Remove grubs by hand when turning over soil. Pots can be soaked in water which should make grubs crawl to the surface as they prefer dry soil. Biological control is another option.
To control infestations in lawn, water well (or wait until heavy rain). Place hessian bags on lawn overnight and remove in the morning. Curl grubs should be found under the bags and can be disposed of (or fed to the local magpies).
CHEMICAL: Most, if not all chemical treatments sold for Curl grub control are not authorised for use on food crops. They are highly toxic to the soil food, web killing earthworms and most other fauna. Less toxic treatments have a poor/inconsistent success rate. EcoNeem and EcoGrub yield mixed results. Repeat treatments will be needed as new eggs are laid throughout the season.