PREVALENCE OF SOIL-BORNE DISEASES OF GREYBACK CANEGRUBS WITH SPECIAL REFERENCE TO ADELINA SP.

Diseases of greyback canegrubs, Dermolepida albohirtum (Waterhouse), were surveyed in 21 fields in the area from Mulgrave (far north Queensland) to Sarina (south of Mackay). Variable infection rates of the pathogens Adelina sp. and Metarhizium anisopliae were found, especially in the area between South Johnstone (south of Innisfail) and Mutarnee (north of Townsville). Neither of the two pathogens was found in the Burdekin. The impact of soil chemistry, tillage intensity and fallowing strategy on the prevalence of the two diseases was investigated. No clear relationship was detected between disease incidence and soil chemistry. In addition, Adelina was shown to survive better under weed cover than under bare soil, and Metarhizium was shown to be fairly tolerant to tillage practices. The life cycle of Adelina was investigated and different stages of the pathogen are recognised in the grub haemolymph. This provides insight into the biology of the pathogen and facilitates further studies on its impact on canegrubs.