Grass-grub, brown beetle

Key characteristics

Grass-grub beetles

• Grass-grub beetles, or brown beetles, are the adult form of the soil dwelling grass-grub. They are about 10 mm long and tan coloured
• The beetles are only present for a few weeks in spring/early summer each year. This period varies in different regions
• They are generally not seen during the day but fly after dusk and are often  attracted to lights in large numbers
• They have two flight phases, the first is a mating flight and occurs very soon after the beetles emerge from the soil, the second consists of feeding flights and may occur for 2-3 weeks
• Grass-grub beetles feed on the young foliage of a wide range of plants including grape vines, kiwifruit, blueberries, cereals, brassicas, ornamental and shelter trees and bushes
• Damage appears as large irregular areas of leaf eaten from leaf margins.

Grass-grub larvae

• Grass-grub larvae are soil dwelling grey/white grubs up to 15 mm long with tan coloured heads
• Typically found lying in a C shape
• Feed on a the roots of many pasture species and other plants
• Damage occurs in discrete patches in pasture
• These initially appear yellower than surrounding pasture and plants are pulled easiliy from the ground
• Patches feel soft underfoot and are easily pugged.

Information prepared by AgResearch