The Biology of the Cacao Webworm, Pansepta Teleturga Meyr. (Lepidoptera: Xyloryctidae) in Papua New Guinea.

Abstract

The cacao webworn occurs on the main islands of New Guinea, New Britain and New Ireland. Originally inhabiting native trees, this species has become adapted to a number of introduced species, including cacao. Trees are damaged by larvae channelling into branches; this restricts the growth of young trees, but the effect on the yield of mature trees is difficult to assess. The non-feeding adult stage lasts 3 days, the egg stage 3-5 days, the larval stage within the range of 8-12 weeks and the pupal stage about 3-4 weeks. The dynamics of larval populations at four sites in New Britain were studied for two years. Distinct larval generations occurred at the rate of about 2.5 per year, each generation lasting about 16-20 weeks. Their occurrence could not be readily related to environmental factors. The main mortality appeared to be during the free-living stage, after egg hatch and before establishment of a larval channel. Larvae were highly aggregated on trees. A small number of trees in the field appeared to be resistant to webworm attack. The possibility of selecting cacao clones for resistance to webworm attack is discussed. Removal of shade from cacao increased webworm numbers but this factor alone could not explain the pest status of cacao webworm.