Chrysomphalus dictyospermi (Morgan)
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea, Diaspididae.
Common name: Dictyospermum scale; Morgan’s scale.
Geographical distribution: Cosmopolitan, occurring throughout the Mediterranean and most subtropical regions; CIE Map #3, 1969 (revised).
Host plants: Polyphagous, in the Middle East mainly on citrus and mango.
Morphology: The body of the female is ovoid, yellow, 1.5 mm in length. The pygidium has three rounded lobes, the median pair largest, each lobe with 1-2 paraphyses. The dorsal, slender macroducts are one-barred and the anus is located about one-third the distance between the median lobes and the vulva, the latter surrounded on either side by 5-8 perivulvar pores. The shield is round, reddish-brown with hyaline margins, the juvenile exuvium slightly off-center. The winged male is yellow with red spots, about 1 mm in length, its dark-grey shield is elongated, 1.5 mm long; and the 1st instar exuvium is placed off-center.
Life cycle: The pest completes 2-3 annual generations in the Middle East, crawlers appearing in spring, in mid-summer and late summer, with much overlap in their occurrence. In warmer regions another generation may be raised. Each female produces about 100-150 eggs; the emerging spring-generation crawlers settle on the upper surfaces of mature leaves, later-generation scales also infest the young fruit and green twigs.
Economic importance: In Israel Morgan’s scale is a minor pest of mango, whereas in eastern Turkey (and other Mediterranean countries) it is a major pest of citrus. Damage is due to causing leaf yellowing and drop, disfiguring fruits by inducing pitting and by reducing plant growth.
Management
Chemical control: White oils and organophosphates can control the pest.
Biological control The main natural enemies of this pest on citrus in western Turkey are the aphelinid ectoparasitoid Aphytis melinus DeBach and several coccinellids; together they control the pest unless disrupted by pesticides. The encyrtid Comperiella lemniscata Compere and Annecke attacks the pest in Spain.
References
Benassy, C. and Soria, F. 1964. Observations ecologiques sur les cochenilles diaspines nuisible aux agrumes en Tunisie. Annales de l’Institute National de la Recherche Agronomique de Tunisie 37: 193-222.
Pina, T., Martinez, B., and Verdu, M.J. 2001. Presencia en la Peninsula Iberica de Comperiella lemniscata (Hym.: Encyrtidae) sobre el piojo rojo de los citricos, Chrysomphalus dictyospermi (Hemiptera: Diaspididae). Boletín de Sanidad Vegetal Plagas 27: 29-34.
Salama, H.S. 1070. Ecological studies on the scale insect, Chrysomphalus dictyospermi (Morgan) in Egypt. Zeitschrift fur Angewandte Entomologie 65: 427-430.
Soydanbay (Tuncÿureck) M. 1977. Effet des Aphelinides parasites sur la population de cochenilles diaspines nuisible aux citrus dans la partie égéenae de la Turquie. Fruits 32: 428-431.