Coleopteran Pests

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Beetles are the largest group of animals and organisms in general with more than 300,000 named species. About 50% of all insect species, 30% of all animal species and 24 % of all organisms are beetles. In PNG there are probably more than 25,000 species of beetles, making almost 10% of the world’s total. However, many species are yet to be described. The order is divided into more than 500 families, belonging to four suborders. About two thirds of the families are believed to occur in PNG. The evolutionary success of this insect order is mainly due to the development of elytra protecting the hindwings when not in use and allowing the occupation of cryptic (hidden) habitats by the adults. The elytra also protect beetles from predation and infection by microorganisms.

Most adult and larval beetles are herbivores or predators of other insects. Some beetles are scavengers on decomposing organic matter. Usually adults and larvae of the same species have the same feeding habits, eg. both are phytophagous. A wide range of beetles is of economic importance since they interfere with agricultural and forestry crops, timber products, stored products, etc. However, beetles do not transmit any diseases of man or livestock. Due to the fact that there are many predators, herbivores and scavengers amongst the beetles, they play an important role in maintaining the ecological balance in natural systems. Furthermore, many host-specific species are in use as biocontrol agents of insect pests and noxious weeds. Apart from this, many beetles are important for the pollination of plants, mainly by means of walking on smaller, inconspicuous flowers such as Umbelliferae. Most of these flowers release a carrion-like scent that attracts beetles but which humans find unpleasant.

There is a large number of beetles that are considered as pests of tree crops in Papua New Guinea. The number of detrimental beetle species found in PNG reflects the diversity of this order - the largest insect order. Both larval and adult beetles have chewing mouthparts and can virtually make use of any plant tissue. Most beetles are associated with wood, that is bored and tunnelled by the grubs and/or the adults. A smaller number of beetles feed on bark and the cambium, respectively. Only a few beetles like the leaf beetles Rhyparida coriacea and Paropsis spp. (Chrysomelidae) as well as Oribius spp. (Curculionidae) feed on the foliage of their host plant. Some important coleopteran pests are:

• Hoop Pine Weevil Vanapa oberthuri (Curculionidae) on Hoop and Klinkii Pines
• Agrilus viridissimus and Agrilus opulentus (Buprestidae) on Talis and Kamarere
• Pin- and Shot-Hole Borers or Ambrosia Beetles (Scolytidae and Platypodidae) on various host trees
• Hylurdrectonus araucariae (Scolytidae) on Hoop Pine
• wood-boring weevils (Curculionidae) on various host plants
• wood-boring longicorn beetles (Curculionidae) on various host plants
• leaf beetles (Chrysomelidae) on Eucalyptus spp.
• powderpost beetles (Bostrichidae and Anobiidae) on various host trees
• Xylotrupes gideon (Scarabaeidae) on various host trees
• leaf feeding Oribius spp. (Curculionidae)

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© Michael F. Schneider, 1999