Biology, damage levels and control of red-banded mango caterpillar in Papua New Guinea and Australia

• Department of Agriculture, Fisheries and Forestry, Australia
• National Agricultural Research Institute, Papua New Guinea
• National Agriculture Quarantine and Inspection Authority, Papua New Guinea

The Red Banded Mango Caterpillar (RBMC) is widespread throughout Southeast Asia, although numbers in many areas are low. Papua New Guinea has RBMC present, as do a few islands in the Torres Strait, separating PNG from Australia. Mainland Australia was free of the caterpillar until recently, when small numbers were detected in feral mango trees on the tip of the Cape York Peninsula.

Little is known about the biology of the RBMC, despite the significant losses it can inflict on mango orchards. In Indonesia and PNG losses of 30-40 per cent of mangoes on infected trees are common, and as high as 80 per cent in some places. Pest management is dependent on understanding the lifecycle, strengths, weaknesses and behaviour patterns of the RBMC, and knowledge of its natural enemies. Without this knowledge efforts to eradicate pests may lead to adverse consequences for other insects, as well as losses of fruit quality and productivity.

This project was undertaken to increase the knowledge of the pest's biology, damage potential, host range and control methods as well as discovering and developing a synthetic based pheromone monitoring system to aid detection in northern Australia.

The caterpillars feed on mango fruit in all stages of development. First and second instar caterpillars feed just beneath the skin surface, tunnelling towards the seed. Later instars feed on the seed itself. Secondary pests such as bacteria and fruit flies may also invade the fruit making it unsuitable for consumption. Improved knowledge of this lifecycle would help determine potential controls, both to eradicate and prevent pest losses. The following tasks were undertaken:
analysis of previous data gathered by PNG scientists, to allow a technical write up of material
analysis and identification of aliphatic compounds derived from RBMC pheromone glands to develop an effective lure dose, allowing field evaluation of a trap design and placement
rearing and maintenance of RBMC in laboratory culture in PNG to learn more about its lifecycle
subjecting field and laboratory populations to various stimuli to determine triggers to start and break diapause (gaps in the development cycle)
observation of selected populations under laboratory and field conditions in PNG, including quantification of damage to available cultivars
observation of host range in field and conduct of alternative host feeding tests
conduct of field trials to select the most suitable controls.

A collaborative investigation between HortResearch NZ, QDPI&F, and NARI and NAQIA PNG identified and successfully tested a synthetic blend of the sex pheromone for this serious pest of mango fruit. Currently found in various countries in Southeast Asia, PNG, the Torres Strait and, more recently, near Bamaga on the tip of Cape York, this pest poses a threat to all mangoes including both commercial and domestic crops. The pheromone, which is now available commercially from HortResearch, will be a useful tool to assist in the early detection through quarantine surveillance and can also be used in mating disruption if required

Chemical treatment options for the control of RBMC in orchards were identified in field trials, however opportunities for broader evaluation did not occur. Studies on the biology, alternative host species and biological control practices were not conclusive and require further investigation.