Biological control of Pulvinaria urbicola (Cockerell) (Homoptera: Coccidae) in a Pisonia grandis forest on North East Herald Cay in the coral sea

Abstract

During 1993-2000 the soft scale insect Pulvinaria urbicola (Cockerell) caused complete destruction of a 16 ha Pisonia grandis R.Br. forest on Coringa South West Islet in the Coringa-Herald National Nature Reserve 400 km off the north-east coast of Queensland, Australia. In March and August 2001, scale surveys on a nearby cay, North East Herald, showed a worrying increase in numbers. Releases of the natural enemies Cryptolaemus montrouzieri (Mulsant) and three parasitioids - Coccophagus ceroplastae (Howard), Euryischomyia flavithorax (Girault) and Metaphycus luteolus (Timberlake) were made in August 2001. C. montrouzieri quickly increased to very high numbers on the pulvinaria scale and the percentage of infested leaves dropped from 25% in August to 8% in December 2001 to 0.01% of leaves by August 2003. All three parasitoids established and parasitism was evident on 30% of infested leaves after nine months. By 2004, C. ceroplastae was the dominant parasitoid and is expected to play an important role in maintaining the scale population at its current low level.