Possible risk posed by drift of the insect growth regulator pyriproxyfen to the rare dung beetle Circellium bacchus (F.) in a national park

Aerial drift of the juvenile hormone analogue (JHA), pyriproxyfen (Nemesis 100 ec®), used to control red scale on citrus on farms close to the Addo Elephant National Park in South Africa, was suspected of causing a decline in a population of the rare dung beetle species Circellium bacchus (F.) in the Park. The effect of pyriproxyfen on fertility and egg viability, as well as larval, pupal and callow adult development of C. bacchus was studied in a laboratory assay. Adult beetles, soil surface and the initial dung supply were exposed to pyriproxyfen applied as a spray at 10 times less than the concentration used commercially to simulate spray drift. Exposure of adult beetles to pyriproxyfen did not affect egg production or the viability of eggs, nor did the compound have adverse effects on immature development, indicating that pyriproxyfen is unlikely to be the cause of the observed population depression of C. bacchus.