Parasaissetia nigra (Neitner)
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea, Coccidae.
Common name: Nigra scale.
Geographical distribution: Of apparent African origin, this species is now widely distributed in most tropical and subtropical regions. CIE Map #573, 1997.
Host plants: Polyphagous.
Morphology: The flat body (1.5-2.0 mm in length) of young females is covered by a brownish shield with transecting grey stripes. At maturity the body is very convex, covered by a shiny red-black shield. Body length, which can be up to 5.5 mm, depends on the insect’s host plant and settlement site. The dorsum of the mature female is covered with many polygons that are less pronounced in young females. The dorsal and marginal setae are usually clavate or expanded and each half of the anal plate is triangular, bearing four setae.
Life history: The Nigra scale completes a generation in less than two months at 24ºC when reared on squash in the laboratory, each female producing about 1,000 eggs, reproducing by parthenogenesis.
Economic importance: Damage is due to secreting large amounts of honeydew which is colonized by sooty mold fungi, covering fruits and leaves by a thick black mass. Sporadic economic damage has been reported on avocado, guava, lychee and mango. Abroad it also damages ornamentals and pineapple.
Chemical control: Applications of white oils, aimed at the scale’s young stages, control the pest without damaging its natural enemies. If ants are visiting the colonies of the pest, it may become necessary to deter them by chemical means, such as spreading a granulated pesticide around the tree trunk.
Biological control: Abroad the nigra scale is attacked by several hymenopterous parasites, but their iimpact on the pest is often much reduced due to encapsulation.
Ben-Dov, Y. 1978. Taxonomy of the nigra scale Parasaissetia nigra (Nietner)(Homoptera, Coccoidea, Coccidae), with observations on mass rearing and parasites of an Israeli strain. Phytoparasitica 6: 115-127.
Blumberg, D. and Goldenberg, S. 1991-1992. Encapsulation of eggs of two species of Encyrtus (Hymenoptera: Encyrtidae) by soft scales (Homoptera: Coccidae) in six parasitoid-host interactions. Israel Journal of Entomology 25-26: 57-65.
Williams, D.J. and Watson, G.W. 1990. The Scale Insects of the Tropical South Pacific Region. Part 3. The Soft Scales (Coccidae) and Other Families. CAB International, Wallingford, UK.