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

The population dynamics of the white wax scale, Ceroplastes destructor News tead, was studied intensively in four easy-peel citrus orchards in the West ern 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 prima rily by parasitoids, predators and miscellaneous factors. Parasitoids and m iscellaneous factors acted as density-dependent regulatory agents during th e pre-ovipositional and first instar stages respectively. This has implicat ions 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.