Hemipteran Pests

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Hemipterans are insects such as true bugs (Heteroptera), cicadas (Cicadidae), aphids or plant lice (Aphididae, Adelgidae), lerps or psyllids (Psyllidae), scale insects (Coccidae), felted scales (Eriococcidae), mealy bugs (Pseudococcidae), white flies (Aleyrodidae) and many more. These insects are of economic significance since there is hardly any crop that is not attacked by at least one hemipteran pest. One common feature of the insects of this diverse group is the piercing-sucking mouthparts that are inserted into plant tissue (show drawing). The typical signs are brown or black feeding punctures visible on the affected plant tissues (show photo). Another conspicuous sign is honey dew, a sweet excretion that is released by the sucking insect. Often ants are attracted to feed on the honey dew. Furthermore, a fungus, the black sooty mould is growing on the honey dew that dripped on to the leaves. Many insects of this group carry viral and bacterial diseases of their respective host plants, often resulting in the necrosis of the punctured leaf or shoot. Furthermore, the piercing-sucking action of some Hemiptera can induce the tumour-like growth of the affected part of the host plant. A number of true bugs like Austromalaya sp. (Pentatomidae), Mictis profana, Leptoglossus australis, Pternistria spp. (Coreidae) feeding on broad-leaf hosts are only of minor importance.

Homopteran bugs are much more significant in terms of their destructive potential due to their smaller size and the resulting higher reproductive potential. Little is known about the biology of the pine woolly aphid Pineus pini (Adelgidae) and the red wax scale Ceroplastes rubens (Coccidae). Both pest species feed on Pinus spp. and have occurred only once in the history of PNG’s forestry, restricted to Bulolo only. Pineus pini, also known as P. laevis was apparently introduced accidentally from Queensland with grafting scions. The imposed quarantine restrictions were successful so that the pest could not establish and spread in PNG. Ceroplastes rubens, also affecting Citrus spp. releases large quantities of honey dew. The sooty-mould growing on these sweet secretions densely covers the surface of the needles so that the light absorption by the leaves is restricted resulting in defoliation and loss of height increment. Ceroplastes prefers particular clones of Pinus caribaea, but can be also found on other Pinus species. The infestation usually is more severe in the upper crown and less severe in the middle and lower parts of the crown.

Of importance for several species of Eucalyptus are the lerps Cardiaspina spp. and Glycaspis spp. (Psyllidae).

Infestations of Acacia mangium and Tectona grandis with mealy bugs (Pseudococcidae) and white flies (Aleyrodidae) were recorded in PNG but are of minor economic significance.

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Michael F. Schneider, 1999