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Pacific Pests & Pathogens - Full Size Fact Sheets

Pandanas leaf webworm (389)

Photo 1. Damage by the Pandanas leaf webworm, Aeolarchis sphenotoma.

Photo 2. Larva of the Pandanas leaf webworm, Aeolarchis sphenotoma.

Photo 3. Red-brown pupa, Aeolarchis sphenotoma, bordered by cresent shaped mass of chewed leaf.

Photo 4. Adult Pandanas leaf webworm, Aeolarchis sphenotoma.

Common Name

Pandanas leaf webworm

Scientific Name

Aeolarchis sphenotoma. It was known previously as Erechthias fibrivora, and before that Decadarchis fibrivora, the name under which it was described. It is a moth of the Tineidae, fungus moths.

Distribution

Not known precisely. It has been recorded from Fiji where it is endemic. There is scant literature on this moth. Swaine (1970)¹ says that he did not find it in American Samoa or (Western) Samoa.

Hosts

Pandanas caricosus and Pandanas thurstoni. The local name is voivoi or kieke.

Symptoms & Life Cycle

The larvae or caterpillars do the damage. The larvae web the young leaves together at the tips and feed inside on the outer layers (Photo 1). As the leaves mature, the affected areas become silvery and withered.

The mature larva is about 16 mm long, with a flattened yellow body and red-brown head (Photo 2). The pupa is 9 mm long, red-brown and slightly flattened inside a tough, parchment-like oval cocoon, which is bordered by a crescent-shaped mass of chewed plant tissue and attached to the inside of the webbed leaf (Photo 3).

The adult is 9 mm long and light-brown (Photo 4). The forewings are golden-brown with a V-shaped cream patch; the hindwings are dull-brown, pointed and lightly fringed with thick hairs.

Impact

A serious pest which can cause extensive damage to the leaves. Pandanas caricosis and Pandanas thurstoni are important species in Fiji used for making mats, baskets, fans and other handicrafts. Of the two, Pandanas caricocis is considered the best. It is also said to be used to treat diarrhoea.

Detection & Inspection

Look for the damaged leaves, and the larvae with yellow body and red-brown head.

Management

CULTURAL

During growth:

Cut off the tips of the leaves that are webbed together and destroy them.

CHEMICAL CONTROL

Use any of the following (PDPs, botanicals) insecticides against lepidoptera larvae: chilli, pyrethrum or derris if natural supplies are available (see Fact Sheet no. 56).
Use a commercial microbial insecticide against lepidoptera larvae: Bt (Bacillus thuringiensis), spinosad or the chemically related spinetorum (Success).
Use synthetic pyrethroids. However, these products are likely to kill any parasitoids if they are present and should be avoided, if possible.
Spot-spraying damaged shoots should be sufficient. Avoid 'blanket' spraying entire trees.

AUTHOR Grahame Jackson & Mani Mua
¹Information from Swaine G (1971) Agricultural Zoology in Fiji. Her Majesty's Stationery Office. London.

Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/18: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland and the Pacific Community.

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