Population dynamics of the white wax scale, Ceroplastes destructor (Hemiptera: Coccidae), on citrus in South Africa, with implications for biological control

Abstract

The population dynamics of the white wax scale, Ceroplastes destructor Newstead, was studied intensively in four easy-peel citrus orchards in the Western Cape Province of South Africa over three consecutive years (1997–1999). Key factor analysis was used to determine and quantify the contribution of individual mortality factors to the total generation mortality. Key stage mortality, determined from a cohort life table, was in the third instar and pre-ovipositing female stages. Mortality of C. destructor was caused primarily by parasitoids, predators and miscellaneous factors. Parasitoids and miscellaneous factors acted as density-dependent regulatory agents during the pre-ovipositional and first instar stages respectively. This has implications for biological control of C. destructor. Some of the mortality factors acted either randomly with no reference to the population densities or in an inverse density-dependent manner during the egg-crawler, second or third instar stages.