Lepidopteran Pests

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Lepidoptera (moths and butterflies) are the second most diverse pest insect order outnumbered only by the beetles. There is hardly any cultivated plant that is not attacked by at least one lepidopteran pest. As pollinators of many plants, adult moths and butterflies are usually beneficial insects that feed on nectar using their siphoning proboscis. The caterpillars however almost always have chewing mouthparts that are suitable for feeding on various parts of a plant. Most caterpillars are defoliators or miners of succulent plant tissues.

The larval wood moths (Cossidae) tunnel the heartwood of living trees. They cause gum pockets called ‘bird’s eyes’ and introduce rot resulting in timber degrade. The development from an egg to an adult can take several years during which the larvae burrow a J-shaped gallery of very large diameter. The damage normally does not harm the host and the boreholes are covered after about one year. However, as a result of a large hole, smaller trees can become more susceptible to wind damage. Adult wood moths are some of the largest and heaviest moths with a body weight up to 25 grams. Cossids are less common minor pests and their damage is usually discovered in the saw mill. The red coffee borer Zeuzera coffeae usually attacks coffee plants but can also cause some damage on Eucalyptus deglupta, Terminalia brassii and Casuarina spp.

The larval bag worms or case moths (Psychidae) of the genera Eumeta and Hyalarcta are defoliators of Eucalyptus, the caterpillars of Cryptothelia and Pteroma feed on Pinus. The larvae are typically hidden in cases or bags that are dragged along the surface of the leaf during feeding.

Severe pests of seedlings in nurseries are the larvae of Noctuidae, called cutworms or army worms, for instance Agrotis ipsilon. The immature stages live hidden in soil. The caterpillars emerge from the soil and feed on their host during the night. Typically, a young plant is neatly cut off right above the soil. Partial but complete defoliation or bending of the seedling is also common. If a cutworm problem is severe or persists in a nursery, the seedlings have to be protected by the application of a suitable insecticide.

A number of Pieridae butterflies like Eurema blanda and other species of this genus defoliate Albizia and other leguminous tree crops. Even though the host can be completely and repeatedly defoliated during severe outbreaks, the tree usually survives the attack.

Other major lepidopteran pests belong to the family Lymantriidae. Some defoliators of Pinus spp. and Eucalyptus spp. are Lymantria ninayi, L. rosa, L. novaguinensis, Calliteara queenslandica, Dasychira wandammena.

Some looper caterpillars (Geometridae) are defoliators of Hoop Pine such as the Millionaire Moth Milionia isodoxa and other species of the genus Milionia spp., others affect Pinus spp. like Alcis papuensis, Paradromulia nigrocellata and Terminalias and Kamarere like Hyposidera talcata. Another potential host tree species of earth measuring works is Acacia mangium.

Of economic importance in Pinus spp. plantations are the defoliators Anthela ekeikei and other Anthelidae as well as moths of the genus Syntherata spp. Saturniidae.

Less important are Striglina floccosa (Thyrididae) and Scopelodes venosa (Limacodidae), both feeding on Terminalia brassii.

A severe pest of Toona australis is the Pyralidae moth Hypsipyla robusta hampering attempts to establish Red Cedar in PNG.

Finally, Hyblaea puera (Hyblaeidae) causes regular outbreaks on Tectona grandis.

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© Michael F. Schneider, 1999