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. See Williams and Watson for an extensive listing of hosts in the South Pacific area. The coconut scale is common to tropical and subtropical regions worldwide, especially on islands. According to Taylor this scale disperses primarily with the aide of other creatures such as birds, insects and as is the case in Fiji, by bats. Accidental dispersal by human activities may occur through the transport of tropical nursery plants and goods made from plant material such as coconut leaf baskets Taylor,
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Coconut scale, Aspidiotus destructor Signoret Hemiptera: Diaspididae , is a pest in over 60 plant families and is found globally in tropical and subtropical areas Davidson and Miller , Ben-Dov This armored scale was described by Signoret in and appears to be native to South Asia but has spread around the world, mainly on infested coconut and banana UK CAB International The insect feeds on plant sap from leaves, stems and fruits, causing yellowing, tissue distortion and die back.
The coconut scale is a pest of concern on coconut and other perennial crops due to its relatively short life cycle of around 35 days and multiple overlapping generations per year. Coconut scale is known to be dispersed by birds, bats and insects as well as wind Taylor Figure 1.
Adult female coconut scale, Aspidiotus destructor Signoret, showing eggs under cover. Photograph by Salahud din , University of Florida. Coconut scale is present in nearly all coconut growing countries of the world.
In more northern regions, it is found only in greenhouses or other enclosed areas Danzig and Pellizzari Figure 2. Distribution map for Aspidiotus destructor. Coconut scale resembles other armored scales in that the body is protected by a waxy cover.
Infestations may be noted by the formation of closely packed colonies composed of what resemble miniature fried eggs. Females develop through two nymphal stages, while males have an additional non-feeding pre-pupal stage four immature stages.
Positive identification of coconut scales requires that adult females be slide mounted and the diagnostic characters observed at high magnification. Eggs: Freshly laid eggs are smooth, elongate and whitish, becoming pale yellow over time. Eggs are laid under the scale cover around the body of the female. Mean length and width of eggs are 0. First instar nymphs: Newly hatched nymphs also called crawlers are free-moving and recognized by the presence of legs, antennae, and a pair of bristles at the tip of abdomen.
Crawlers are light green to yellowish brown, translucent and somewhat oblong, with an average length and width of 0. Second instar female: Females remain pale yellow, circular and somewhat transparent in the second instar, which lasts for days. Females nymphs are 0. Male nymphs: Development of male characteristics starts in the middle of the second instar. Male covers become reddish brown and more elliptical in shape, and then transform in stages into the pre-pupal, pupal and adult stages.
The second instar lasts for days for males Williams and Watson, The male pre-pupal and pupal stages are spent under the scale produced by the second instar. Adult females: Adult female coconut scales have a circular or broadly oval cover that is 1. The cover is flat and translucent with a subcentral pale exuviae.
Bodies of slide-mounted specimens are 0. Diagnostic characteristics include: three pairs of lobes with no indication of a fourth pair; plates long, flat and fringed; and with sclerotization on the dorsum of the pygidium Williams and Watson Adult males: Adult male coconut scales are small, two-winged, reddish, gnat-like insects with eyes, antennae, three pairs of legs and long appendages. Adult males do not feed and are short lived. Figure 3. Coconut scale, Aspidiotus destructor Signoret, showing eggs, nymphs and exuviae, and adult female with cover removed.
Figure 4. Coconut scale, Aspidiotus destructor Signoret, male pupa removed from cover. Figure 5. Adult female coconut scale, Aspidiotus destructor Signoret, removed from cover. Figure 6. Adult male coconut scale, Aspidiotus destructor Signoret. Adult females lay eggs in concentric circles under the scale cover over a period of days, and may produce 3 or 4 consecutive batches in their lifetime Taylor Crawlers may emerge while the female has already started laying the next batch of eggs personal observation.
The crawlers move over the leaf surface for hours to find a feeding site Taylor , Waterhouse and Norris After settling, females remain sessile throughout their development; adult males undergo a pseudo-pupation, develop a pair of wings and can disperse by flying to find mates Ghauri Females release pheromones through their anus to attract males Moreno Sexual reproduction is influenced by food availability, but typically the sex ratio is male: female ; although both male and female colonies have been observed Ahmad and Ghani , Taylor Crawlers are the primary dispersal stage of coconut scale within and between host trees.
Ben-Dov reported several hundred hosts from over 60 plant families. Common perennial hosts include tropical fruits and ornamental plants, including banana, coconut, camellia, guava, mango, palm, papaya, breadfruit, ginger, bird of paradise, sugarcane, ficus, apple, plumeria, avocado, citrus, grape and palms.
Coconut scale is considered a major threat to coconut palms throughout the world. It infests at high densities on the undersurface of coconut leaves, as well as on the frond stalks, flower clusters and young fruit. Coconut scale was accidently introduced into the Pacific Islands and became a serious pest until the introduction of parasitoids and predators which achieved significant suppression Waterhouse and Norris This species is reported to preferentially infest older leaves of mango, but it also causes blemishes on the skin of mango fruits which reduces their value.
Coconut scale infests fruits of oil palms and banana and reduces fruit quality Chua and Wood Coconut scale was first reported in Hawaii in on papaya, banana and apple and remains a pest of concern in that region Kessing and Mau Removal of sap from leaves, petioles, peduncles and fruits leads to discoloration, depressions, and tissue distortions on leaves. Coconut scales may possibly introduce toxins into the plant through their saliva Waterhouse and Norris, Figure 7.
Mature mango plant infested with coconut scale, Aspidiotus destructor Signoret, in Pakistan. Figure 8. Mango twig showing discoloration from coconut scale, Aspidiotus destructor Signoret, infestation. Figure 9. Underside of mango leaf infested with coconut scale, Aspidiotus destructor Signoret. Figure Upper side of mango leaf infested with coconut scale, Aspidiotus destructor Signoret, showing chlorosis.
Biological control: Over 40 species of parasitoids and predators, and several fungal pathogens, are known to attack coconut scale Ben-Dov et al. In the absence of these natural enemies, population explosions of this pest can occur. Aphytis melinus DeBach and Aphytis lingnanensis Compere Hymenoptera: Aphelinidae are the most common parasitoid species controlling the coconut scale populations in Fiji and the Philippines DeBach , Watson et al.
In Pakistan, Pakencyyrtus pakistanensis Ahmad Hymenoptera: Encyrtidae was reported as an important parasitoid in mango Ahamad and Ghani, Coccinellid ladybird beetle predators of coconut scale include Chilocorus spp. Aphytis melanus , a parasitic wasp, ovipositing on an armored scale. Cultural control: Pruning and training of fruit trees and proper disposal of infested leaves, branches and twigs will help control scale insects on nursery plants and trees.
Excessive use of plant fertilizers contributes to scale outbreaks. Chemical control: Various insecticides are registered for control of armored scales in ornamental and fruit crops. Crawler stages are generally the most susceptible to insecticides. Contact action insecticides, including horticultural oils, become progressively less effective once the scale insects develop their waxy cover.
Insect growth regulators may be effective, provided they are applied when the immature stages are present. Location of the insect on the plant, growth stage of the plant, and solubility of the insecticide influence the effectiveness of systemic insecticides applied for control of armored scales. Several spray applications at day intervals may be necessary for complete management of a heavy infestation.
The toxicity of insecticides to parasitoids and other beneficial insects should be considered before starting a spray program for scale insects. Since coconut scale is a quarantine pest in many areas, phytosanitary treatment with gamma irradiation has been developed as a potential control measure for this scale Follet Description Back to Top Coconut scale resembles other armored scales in that the body is protected by a waxy cover.
Life Cycle Back to Top Adult females lay eggs in concentric circles under the scale cover over a period of days, and may produce 3 or 4 consecutive batches in their lifetime Taylor Hosts Back to Top Ben-Dov reported several hundred hosts from over 60 plant families.
Economic Importance Back to Top Coconut scale is considered a major threat to coconut palms throughout the world. Management Back to Top Biological control: Over 40 species of parasitoids and predators, and several fungal pathogens, are known to attack coconut scale Ben-Dov et al. Studies on Aspidiotus destructor Sign. An annotated check-list of the insects and allied terrestrial arthropods of Barbados. Other tropical fruit trees and shrubs. In: D. Rosen ed.
World Crop Pests. Elsevier, Amsterdam, the Netherlands, 4: pp Danzig EM, Pellizzari G. Hungarian Academy of Sciences. Budapest, Hungary: pp. Ornamental plants. In Rosen, D ed.
List of symptoms / signs
Aspidiotus destructor Signoret -- Diaspididae. The coconut scale posed a serious problem to the copra industry in Fiji just about the time that the coconut moth, Levuana irridescens B. Coconut scale was first recorded as a pest of bananas in and in of coconuts. Damage was severe enough to cause H. Simmonds, the Government Entomologist in Fiji, to seek natural enemies in Tahiti in where the scale was known to be present in lower numbers. Two parasitic species imported and established were Aphytis chrysomphali Mercet and Aspidiotiphagus citrinus Craw, and by these were distributed to many islands in the Fiji group.
Valid Names Results
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report. Due to the variable regulations around de registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label. APPPC, Insect pests of economic significance affecting major crops of the countries in Asia and the Pacific region.
Coconut scale, Aspidiotus destructor Signoret Hemiptera: Diaspididae , is a pest in over 60 plant families and is found globally in tropical and subtropical areas Davidson and Miller , Ben-Dov This armored scale was described by Signoret in and appears to be native to South Asia but has spread around the world, mainly on infested coconut and banana UK CAB International The insect feeds on plant sap from leaves, stems and fruits, causing yellowing, tissue distortion and die back. The coconut scale is a pest of concern on coconut and other perennial crops due to its relatively short life cycle of around 35 days and multiple overlapping generations per year. Coconut scale is known to be dispersed by birds, bats and insects as well as wind Taylor