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Taro Insects

Contents

A. COLEOPTERA

Taro Beetle

Papuana spp. (Dynastidae)

 

B. HEMIPTERA

Taro Planthopper

Tarophagus proserpina Kirk. (Delphacidae)

Melon Aphid

Aphis gossypii Glover (Aphididae)

 

C. LEPIDOPTERA

Taro hornworm

Hippotion celerio L. (Sphingidae)

Cluster Caterpillar

Prodenia (Spodoptera) litura F. (Noctuidae)

 

D. ACARINA

Spider mite

Tetranychus spp. (Tetranychidae)

 

 

Numerous insect species have been recorded on taro in the Pacific region but only a few are known to cause significant damage. Most of these are non-specific in their food preference and feed on a wide variety of crops and wild plants.

The pests discussed below are those that have frequently been the cause of economic loss either through a direct attack on the taro plant or indirectly because they transmit virus diseases.

 

A. COLEOPTERA

Taro Beetle

Papuana spp. (Dynastidae)

The most important species include P. armi-collis Fairm., P. huebneri Fairm., P. inermis Prell and P. Zaevipennis Arrow.

Distribution - Kiribati, Papua New Guinea, Solomon Islands, Tuvaiu,. Vanuatu.

Description & Biology - The adult is 25 mm long, black and shiny. The male has a slender recurved horn on the head and two projections on the prothorax. The eggs are laid in the soil near the host plant and the larvae, which are white and curled, burrow through the soil and pupate deep underground. The adults bore into the corms.

Damage - Papuana attack reduces the market value of corms and makes them more susceptible to fungal rotting during storage. The effect on yield is variable. In severe infestations the planting material is attacked and killed as the beetle bores into the growing point. Plants that survive this early attack have mature corms with little usable tissue.

Host Plants - Taro, sweet potato, banana, oil palm, coconut.

B. HEMIPTERA

Taro Planthopper

Tarophagus proserpina Kirk. (Delphacidae)

Distribution -  Widespread within the Pacific region. 

Description and biology -  The adult is 4 mm long, black with a broad white band on the back of the thorax and abdomen. The nymphs are creamy white. Eggs are deposited in the midrib of the leaf and at the leaf bases. Feeding and .oviposition punctures cause sap exudations which form red encrustations.

Damage -  Heavy infestations, causing direct damage, have been reported. Transmission of virus particles, which occurs even at low population densities, is more serious. 

Host plants -  Tarophagus is specific to taro.

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Melon Aphid

Aphis gossypii Glover (Aphididae)

Distribution -  Widespread in the Pacific region.

Description and biology  - The adult is 1.5 mm long, dark green to (3) yellow with a black head, cornicles and cauda. Winged adults appear first, then nymphs and wingless adults. All stages live mostly on the undersides of the leaves.

Damage - Sucking of leaves by adults and nymphs causes wilting, especially in dry weather. Large colonies can cause the leaves to curl downwards, Dasheen mosaic virus is transmitted by this insect. 

Host plants - Taro and a wide range of cultivated and wild plants, especially Hibiscus spp. and members of the Cucurbitaceae, are hosts.

 

 

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C. LEPIDOPTERA

Taro hornworm

Hippotion celerio L. (Sphingidae)

Distribution - Widespread in the Pacific region.

Description and biology - The adult moth is 40 mm long with brown forewings and reddish hindwings tinged with black. The mature caterpillar is 80 mm long, green with a cream stripe along the sides. There is a pair of large eye-spots on both of the first two abdominal segments. On the last abdominal segment a reddish black caudal horn is present.

Damage -  The caterpillars chew the edges of the leaves. In severe cases, all the top growth may be consumed.

Host plants -  A wide range of plants, including taro and sweet potato.

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Cluster Caterpillar

Prodenia (Spodoptera) litura F. (Noctuidae)

Distribution - Widespread in the Pacific region.

Description and biology -  The adult moth is 18 mm long, greybrown with paler hindwings. The eggs are laid in clusters and covered with light hair-like scales. The caterpillars are at first gregarious and later solitary. The mature caterpillar is 45 mm long, greybrown above, green below, with a pale stripe and a series of dark spots along the sides.

Damage - The young caterpillars strip the upper surface of the leaf blade. Older caterpillars make holes in the leaves.

Host plants -  A wide range of plants including taro and sweet potato.

 

 

[Click on photo to enlarge]

D. ACARINA

Spider mite

Tetranychus spp. (Tetranychidae)

Distribution -  Widespread in the Pacific region.

Description and biology -  The adult is 0.5 mm. long, cream coloured with a row of three black spots along each side of the body. Eggs are laid singly on the under side of the leaves. The nymphs are pale green.

Damage -  Sucking of leaf tissue by adults and nymphs causes characteristic white speckling along the veins. Chlorosis and early death of leaves may occur, especially in dry weather.

Host plants -  A wide range of plants, including taro and cassava.

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