Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

New research on the coconut scale Aspidiotus destructor (Sign.).

Abstract

From observations in the Ivory Coast on Aspidiotus destructor Sign. on coconut palm, it was found that the pest could easily be destroyed when the trees were young, either by systemic granules containing 10% aldicarb applied twice at monthly intervals to the soil at 4 or 8 g commercial product/tree, or by sprays of methidathion or dimethoate at 40 g/hl. On older trees, predation by coccinellids (especially Chilocorus schioedtei Muls. and C. dohrnii Muls.) was usually sufficient to maintain scale populations below the economic level, except when Oecophylla longinoda (Latr.), an ant preying on the coccinellid larvae, was also present and permitted the scale population to build up; these ants should not be destroyed, however, since they control other coconut pests such as Pseudotheraptus nymphs. The mineral nutrition of the palms appeared to have an important effect on the population dynamics of A. destructor; deficiencies, especially in potassium, favoured multiplication of the scale insect. Since scales tended to develop best on parts of the palms most exposed to light, planting at a higher density should help to reduce the likelihood of infestation. After a heavy attack by A. destructor the nut yield was usually reduced by at least 25% during the next 2-3 years, although some heavily infested trees were able to catch up in production during the 2 years after elimination of the infestation and to yield slightly more nuts than trees that had remained uninfested or only lightly infested.