Preliminary study of attraction to dung of larvae of Tasmanian grass grub ( Aphodius tasmaniae (Hope)): A dissertation submitted in partial fulfilment of the requirement for the degree of Bachelor of Horticultural Science with Honours in the University of Canterbury

Abstract

The importance of the role played by chemical stimuli in the feeding behaviour of insects has often been stressed (Schoonhoven 1968; Hsiao 1969: Dethier 1970). Although there is a considerable amount of literature on chemical attractants, in the majority of cases, studies have involved adult insects. Studies of chemical attraction of larvae have been comparitively neglected, despite larval stages being frequently the most damaging. Work done on grass grub (Costelytra zealandica White ) showed that third instar larvae respond to an olfactory attractant in parsnip and carrot roots, and freshly ground nutmeg. Laboratory tests led to the discovery of a of a particularly potent larval attractant α- fenchol (Osborne and Boyd 1974). Work with Tasmanian grass grub (Aphodius tasmaniae Hope) also indicated a response to attractants in natural products. Boyd (1974 pers. comm.) noted in a lucerne paddock at Green park, larvae were almost exclusively confined to sheep dung patches. There was also some attraction to dung in experimental conditions. The Tasmanian grass grub is an important pest in southeast Australia (Swan 1934; Madge 1952; Carne 1956; Maelzer 1962a) but is regarded as a minor pest in New Zealand. It is limited to drier soils and has only been observed causing damage in recent years. It has been known to occur in Canterbury since 1920, but apart from a few insecticide trials, little research has been done in New Zealand (Pottinger 1968). As larvae of Tasmanian grass grub come up to and can move freely on the soil surface in search for food, a larval feeding attractant in combination with an insecticide could be a useful method of control. The objective of this study was to determine the presence of a feeding attractant for Tasmanian grass grub larvae in dung, and to attempt to isolate the active components.