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Aspidiotus destructor (Coconut scale)
General information
The coconut scale is a common pest of coconut and banana. It also infests many other trees and ornamental plants, some of the hosts include avocado, bird of paradise, breadfruit, ginger, guava, mango, mock orange, mountain apple, palm, papaya, pandanas, plumeria and sugarcane.
Symptoms
- Saliva produced during feeding is toxic and causes yellowing on the leaves (Waterhouse & Norris, 1987)
- Withering of the infested leaves
- Discoloured streaks on fronds
Severe infestation on coconut (Source: Infonet B. Loehr)
Taxonomic information
Category - Insect
Domain - Eukaryota
Kingdom - Metazoa
Phylum - Arthropoda
Class - Insecta
Genus - Aspidiotus
Species - destructor
Distribution
The coconut scale is common to tropical and subtropical regions worldwide, especially on islands. It was first found in the State on Oahu in 1968 and has since spread to Kauai, Hawaii and Maui. It is reported in American Samoa, Fiji, French Polynesia, Hawaii, Irian Jaya, New Caledonia, Papua New Guinea, Solomon Is., Sri Lanka, Vanuatu and Western Samoa.
Prevention and Control
Natural enemies
- Around 40 species of predators and parasites have been reported to attack the coconut scale in areas outside of Hawaii (Beardsley, 1970). Several of these natural enemies have been used to successfully control outbreaks of this scale (Sweetman, 1958)
- The coccinellid beetle, Cryptognatha nodiceps (Marshall), was introduced to Fiji and effectively controlled this scale (Taylor, 1935).
- Chilocorus politus (Mulsant), has been effective in Mauritius and Indonesia (Beardsley, 1970).
- Ladybird beetles have been effective throughout the Tropics, especially Pseudoscymnus anomalus, Cryptognatha nodices, C. gemellata, Rhyzobius satelles, Chilocorus nigritus and C. malasiae (the last four are non-specific predators) (Waterhouse & Norris, 1987)
- Cryptognatha nodiceps has a long adult life, high reproductive capacity, good dispersal abilities, and is a voracious predator with a preference for the coconut scale (Waterhouse & Norris, 1987).
- In Hawaii, two coccinellid beetles, Telsimia nitida(Chapin) and Lindorus lophanthae (Blaisdell), were introduced to control other scale pests and are the principal predators of the coconut scale (Beardsley, 1970).
- Other natural enemies in Hawaii are the predaceous thrips, Aleurdothrips fasciapennis (Franklin) and two-minute aphelinid wasps that are internal parasites of the coconut scale (Beardsley, 1970).
- Chemicals used on scales are usually the same as those used on mealybugs and may include diazinon, dimethoate, formothion, malathion and nicotine (Copland and Ibrahim, 1985).
- Sprays are only effective on the crawler stage of scales.
- Chemical applications should be used only when parasites are not economically effective.
References
- Williams, D. J. and G. W. Watson. 1988. Aspidiotus destructor Signoret. pp. 53-56. In: The Scale Insects of the Tropical South Pacific Region Part 1: The Armored Scales (Diaspidae). The Cambrian News Ltd. 290 pages.
- Waterhouse, D. F. and K. R. Norris. 1987. Biological Control: Pacific Prospects. ACIAR, Inkata Press, Melbourne, Australia, see pp. 62-71.
- Beardsley, J. W. 1970. Aspidiotus destructor Signoret, an Armored Scale Pest New to the Hawaiian Islands. Proc. Hawaii. Entomol. Soc. 20: 505-508.
- Sweetman, H. L. 1958. The Principles of Biological Control. Wm. C. Brown Co. Dubuque, Iowa. 560 pp.
- Taylor, T. H. C. 1935. The Campaign Against Aspidiotus destructor, Sign., in Fiji. Bull. Entomol. Res. 26: 1-102.
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