Prickly acacia, Acacia nilotica subsp. indica (Benth.) Brenan, a major weed of
the Mitchell Grass Downs of northern Queensland, Australia, has been the target of
biological control projects since the 1980s. The leaf-feeding caterpillar Cometaster
pyrula (Hopffer) was collected from Acacia nilotica subsp. kraussiana (Benth.) Brenan
during surveys in South Africa to find suitable biological control agents, recognised as a potential agent, and shipped into a quarantine facility in Australia. Cometaster pyrula has a life cycle of approximately 2 months during which time the larvae feed voraciously and reach 6 cm in length. Female moths oviposit a mean of 339 eggs. When presented with cut foliage of 77 plant species, unfed neonates survived for 7 days on only Acacia nilotica subsp. indica and Acacia nilotica subsp. kraussiana. When unfed neonates were placed on potted plants of 14 plant species, all larvae except those on Acacia nilotica subsp. indica and Acacia nilotica subsp. kraussiana died within 10 days of placement.
Cometaster pyrula was considered to be highly host specific and safe to release in
Australia. Permission to release C. pyrula in Australia was obtained and the insect was first released in north Queensland in October 2004. The ecoclimatic model CLIMEX
indicated that coastal Queensland was climatically suitable for this insect but that inland areas were only marginally suitable.
