PEST ADVISORY LEAFLET NO. 38 Plant Protection Service Secretariat of the Pacific Community 2004 COCONUT SCALE INSECT Coconut scale insect Aspidiotus HOST RANGE AND PEST causes shrivelling of nuts leading to destructor Signoret (Hemiptera: STATUS premature nut fall. Young coconut Dispididae) (CSI) is recorded in trees aged 10-15 years are most tropical and subtropical regions CSI is a highly polyphagous diaspid vulnerable to CSI damage. worldwide and is present in nearly all scale. Although it is most notable on countries where coconuts are grown. coconuts, it is a well known pest of On bananas, the scale attacks the It is also known as armoured scale, tropical crops belonging to many whole plant: leaf, leaf petioles and transparent scale, bourbon scale, families. psuedo-stems, causing stunting of the bourbon aspidiotus, and sometimes plants. Infested fruit are deformed called red flies because of the CSI hosts are typically perennial and unmarketable. Severe attacks abundance of male flies during late species and include many species of can kill the plants. afternoons in case of severe fruit trees, such as avocado, outbreaks. breadfruit, mango, guava and papaya. Damage to fruit trees causes leaf fall, Other major hosts are cocoa, cassava, stunting and dieback of the plants. CSI infests stems, branches, leaf- cotton, kava, oil palm, papaya, rubber, Scale presence on fruit cause petioles, leaves and fruits of their host sugarcane and tea. It also attacks a blemishes, and fruits are deformed plants. It is found mostly on the range of ornamental plants including and unmarketable. undersides of leaves. During severe roses. outbreaks, scale insects completely Shrubs such as roses can be severely cover the underside of leaves and Coconut is its preferred host. CSI is affected by CSI attacks causing defoliate and even kill their host plants. found mainly on the underside of stunting that may lead to secondary leaves, but frond stalks, flower infections and finally collapse of the After accidental introduction to some clusters and young fruit can also be plant. Pacific islands, CSI became a very attacked.During heavy infestations serious pest of coconuts until the they attack the upper side of coconut initiation of biological control, following leaves as well. Attack on fruits which, almost invariably, its pest status in many countries has been greatly reduced. Recently it has spread to new areas and in the absence of natural enemies it has become a serious pest. DISTRIBUTION IN THE PACIFIC REGION The following countries in the region record the presence of the CSI. American Samoa, Fiji Islands, French Polynesia, Guam, Marshall Islands, Federated States of Micronesia, New Caledonia, Northern Mariana Islands, Papua New Guinea, Samoa, Solomon Islands, Tuvalu, Vanuatu, Wallis and Futuna, Tokelau. Figure 1: Coconut Scale Insect on coconut leaf The scales suck sap from the plant clearly visible from a great distance. The first-instar crawlers are about and inject toxins from its salivary In extreme cases, the leaves dry out, 1mm in length, yellowish-brown, oval glands. entire fronds drop off and the crown and translucent. Second-instar dies. Heavy infestation results in females are stationary and secrete a A secondary effect of the CSI is stunting of new leaves, reduction of translucent wax cover. The second- development of sooty mould on plant crop yield or complete crop failure. instar males are smaller than the surfaces, especially on leaves, which Infested coconut fronds exhibit yellow females. They group together, secrete stops photosynthesis. A sweet areas on the upper surface, formed a filamentous waxy material and excretion attracts ants, which scare by numerous yellow spots each become immobile. The male pre- away the natural enemies of the scale marking the position of the coconut pupal and pupal stages are spent and assist in spread of crawlers. scale on the under surface. under the scale produced by the second-instar stage. CSI is known to attack the following DESCRIPTION, BIOLOGY AND plant species: ECOLOGY The females have two nymph stages. Annona muricata (soursop), The males have four, two feeding, a Artocarpus altilis (breadfruit), The life cycle of A. destructor pre-pupal and a pupal stage. Camellia sinensis (tea), Capsicum typically lasts 32 to 35 days. The spp., Cassia spp. (sennas), Ceiba larvae (crawlers) and adult males are The scale cover of the adult female pentandra (kapok), Cocos nucifera the only mobile stages of the scale. is oval to circular, 1.5-2.0 mm across, (coconut), Carica papaya (pawpaw), The first-instar crawlers leave the flat, thin and translucent. The pale Cinnamomum zeylanicum maternal scale and begin feeding by yellow exuviae are more or less (cinnamon), Citrus spp., Colocasia inserting ‘feeding tubes’ on the central on the scale. Inside the scale esculenta (taro), Cucumissativus affected part of the plant surface. The the yellow adult female measures 0.6- (cucumber), Dioscorea spp. (yam), crawlers of both sexes are mobile. 1.1 mm across. Adult males are more Elaeis guineensis (oil palm), They can move only to a limited reddish than females, but much Eucalyptus deglupta, Eugenia, distance on the affected plant. They smaller and more oval. The male has Euphorbia (spurges), Ficus carica mostly depend on other agents - wind, one pair of wings and is motile. (fig), Hevea brasiliensis (rubber), birds, other animals, ants, etc. - for Hibiscus (rosemallows), Myristica dispersal. Heavy rains wash off the CONTROL MEASURES fragrans (nutmeg), Lycopersicon crawlers from their hosts. esculentum (tomato), Plumeria CSI can be easily be re-introduced, (frangipani), Mangifera indica The eggs are yellow and very small. even if it is successfully controlled on (mango), Musa spp. (banana), They are laid underneath the scale the primary host crop, because of its Pandanus (pandanus), Passiflora around the body of the female. The wide host range. edulis (Passionfruit), Persea female deposits 20-50 eggs over a americana (avocado), Rhizophora, period of few days. Incubation takes Phytosanitary Measures Piper nigrum (black pepper), Piper 7 to 8 days. After hatching, the CSI is spread by people moving methysticum (kava), Prunus persica nymphs crawl out and colonise the infested plants or plant parts. (peach), Raphanus (radish), Psidium plant surfaces. Quarantine border surveillance should guajava (guava), Saccharum be strict on the movement of planting officinarum (sugarcane), Solanum material to avoid spread of scale. nigrum (nightshade), Spondias purpurea, Syzygium aromaticum (clove), Tamarindus indica (tamarind), Theobroma cacao (cocoa), Vitis vinifera (grapevine), Xanthosoma sagittifolium (yautia (yellow)), Zingiber officinale (ginger), Vigna unguiculata (cowpea). DAMAGE SYMPTOMS On leaves, A. destructor causes scales with yellow spots developing where the crawlers have settled and grown into adults. Entire leaves may turn yellow to brown and fall. Sooty mould may develop. The bright yellow colour of affected coconut palms is Figure 2: Larvae of predatory ladybird beetle Telsimia nitida Cultural Control CSI can be eradicated from new areas by destroying infested plants and plant parts. The scale, however, is known to establish very quickly because of its wide host range and is therefore difficult to eradicate. Healthy plants in well-drained soils are seldom seriously infested. Weak and neglected plantations are particularly susceptible to damage by A. destructor. Biological Control Biological control of the pest is the long term solution. In the countries where the scale is present, the pest population is controlled by introducing natural enemies. In recent years Figure 3: Adult beetle of predatory ladybird Telsimia nitida introduction of natural enemies has controlled the pest in Tuvalu and on Trinidad into Fiji in 1928 (Kamath, REFERENCE the island of Rotuma in Fiji. 1979). C. nodiceps has since been introduced to a number of Pacific Kamath, M. K. 1979. A review of However, biological control takes time Island countries and territories. The biological control of insect pests and to establish and become effective and other predatory coccinellids, noxious weeds in Fiji (1969 - 1972). occasionally there are pest outbreaks Chilocorus nigritus, C.circumdata, Fiji Agricultural Journal. 41: 55-72. due to imbalance or loss of natural P. anamolus and T. nitida have also enemies. This imbalance or loss of been successfully introduced and Waterhouse, D. F. and K . R. Norris. natural enemies occurs due to natural established in many of the Pacific 1987. Biological Control Pacific causes such as droughts,, cyclones, Islands. Prospects. 62-71. etc. In such cases introduction of new stocks of the natural enemy may be To cater for occasional peak demands necessary. from Pacific islands for CSI natural enemies, the predators are reared Natural enemies of other scale insects under laboratory conditions at SPC may adapt to feeding on A. destructor Plant Protection Sevice in Fiji and field as it colonises new areas. The scale released where necessary. is attacked by a few specific and a large number of non-specific Chemical Control parasitoids and predators. The use of chemicals is not usually recommneded as a pest control Predators rather than the parasitoids method, especially on coconuts. play a significant role in limiting CSI Pesticides can also kill the natural populations (Waterhouse and Norris, enemies present in the field. There 1987). The most common are the are, however, a number of insecticides coccinellid beetles, Chilocorus