California red scale (Homoptera: Diaspididae) phenology on citrus in South Africa

Male California red scale, Aonidiella aurantii (Maskell), were monitored with sticky traps which incorporated synthetic female pheromone in rubber septa at six climatically different locations in South Africa. The males exhibited a two- or three-cohort population structure on citrus and resulted in four to six generations per year on orange trees, Citrus sinensis (L.) Osbeck (verus three to four generations in California) and five to seven generations per year on lemon trees, C. limon (L.) Burm. The mean intergeneration periods (IGPs) (+/-SEM) between related population peaks on the traps in degree-days, accumulated between developmental thresholds 11.7 and 37.8 degrees C, were 498.2 (+/-7.43) on 'Eureka' lemon trees, 576.8 (+/-4.12) on orange cultivars, and 609.6 (+/-16.29) on 'Marsh' grapefruit trees, C. paradisi Macf. The IGPs for lemon and grapefruit trees were shorter than California estimates based on constant temperature developmental data, but the mean IGP on orange trees was very similar to field values obtained in California and Swaziland. The use of a designated flight peak for the prediction of fruit infestation levels at harvest will be difficult where a three-cohort population structure exists