Aspects of the biology and population dynamics for the integrated control of the mango scale Aulacaspis tubercularis Newstead in South Africa

Abstract

Post embryonic development of the mango scale, Aulacaspis tubercularis Newstead, comprises of two larval instars and an imago in the female, and two larval instars, two pupal instars (prepupa, pupa), and an imago in the male. The sex of the organism can easily be determined in the first in star. The duration of a single generation of A. tubercularis at simulated summer, spring and winter temperatures was 42,7, 52,5 and 68,9 days respectively. Average periods of oviposition at the same simulated conditions were 33,25, 45,69 and 28,48 days and the average number of eggs produced 203, 15, 261,90 and 82,45 for summer, spring and winter respectively . Males accounted for 73% of the A. tubercularis population. A. tubercularis was found to be biparental, no parthenogenesis was found and positive phototaxic behaviour was demonstrated. Population expansion in the field began at the beginning of spring and reached a peak before midsummer. This can possibly be explained by the higher reproductive rate of the insect when reared under simulated spring conditions in the laboratory. The mango scale population peaked in August and November in Kaapmuiden and Nelspruit respectively. The infestation of mango scale in mango trees was significantly higher in the shady south facing lower aspect than in any of the other aspects. Generations overlapped to such an extend that all developmental stages were found throughout the year . The long ovipositional period, which can last up to 82 days in spring, is primarily responsible for the overlapping of generations. The only indigenous parasitoid found on mango scale in South Africa, Aspidiotiphagus citrinus, is density independent and therefore incapable of controlling A . tubercularis. A predatory th rip, Aleurodothrips fasciapennis, was found feeding on A. tubercularis. This is the first recording of this species on mango scale and in Africa.