Control of grass grub (Coleoptera: Scarabaeidae) with rollers of different design

Abstract

Abstract Three different types of roller, single or tandem (twin) with rigid rollers, and pneumatic (rubber-tyred), were used with one pass on pasture infested with grass grub (Costelytra zealandica (White)) to examine their effect on grass grub and earthworm mortality, and subsequent pasture yield. The rigid tandem rollers had three types of surface—smooth, grooved, and knobbled. The first two of these were tested with three different diameters and under five different loads. A spiked roller was also used. All rollers were towed at 2.8 km/h. The heaviest tandem rollers with grooved or knobbled surfaces caused 77–88% mortality of immature third instars which was 18% of the population present. Second instars and mature third instars were not significantly affected. Depression of the soil surface increased linearly with roller weight and the amount of depression could be used to predict the mortality of immature third instar larvae. There was no significant difference in grass grub mortality or pasture resp...