Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

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Cashew scale (383)

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Photo 1. Cashew scale, Pseudaonidia trilobitiformis, on skin of orange.

Photo 2. Enlargement of Photo1 showing sub-circular female cashew scales, Pseudaonidia trilobitiformis, and the off-centre skin of the earlier moult.

Photo 3. View of slide-mounted adult,  Pseudaonidia trilobitiformis.

Summary

• Worldwide distribution. In Oceania, Australia, Fiji, French Polynesia, New Caledonia, and Vanuatu. Host range wide: Barringtonia, capsicum, chilli, citrus, coconut, coffee, mango, frangipani, Ficus, woody legumes.
• Cover of female, semi-circular, 2.5-3 mm, domed, yellowish-brown, remains of first molt, clearly seen off-centre. Body of female, wine-red.
• Damage: an important pest of citrus, cashew, cocoa.
• Spread by 'crawlers' carried in wind, birds, clothing, machinery. Movement of nursery stock.
• Natural enemies: ladybird beetle (New Caledonia, Vanuatu) and wasp parasitoid (New Caledonia).  
• Chemical control: lime sulphur or wettable sulphur (follow manufacturers' instructions because of phytotoxicity concerns); alternatively, use insecticideal soap, white or horticultural oils. Note, avoid malathion and synthetic pyrethroids as they will destroy natural enemies.

Common Name

Cashew scale. It is also known as the trilobite scale.

Scientific Name

Pseudaonidia trilobitiformis. It was previously recorded as an Aspidiotus species, and as Pseudaonidia darutyi. [Note, a definitive identification of the scale on citrus from Fiji is awaited. The scale was provisionally identified using photos on orange. It is more usually found on leaves.]

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