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Saissetia oleae (Olivier)

Olive scale or black scale
[Saissetia oleae]. L: immature female. R: mature female.

[Saissetia oleae]. L: immature female. R: mature female.

Olivier named this species oleae in 1791, presumably because it was found on olive trees. It is one of the "H" scales that have ridges on the top shaped like an "H".

Status in New Zealand: an exotic (adventive) species, first recorded here in 1885. Olive scale is an important citrus pest, particularly in Gisborne. It is recorded on 20 exotic plants and 23 native plants here, and can be a problem in gardens. Its range is from The Kermadec and Three Kings Islands, throughout the North Island and most of the South Island.

Biology: one generation per year in New Zealand, overwintering on the twigs as immature females. The new generation is produced through summer. Olive scale is usually parthenogenetic  but males are found occasionally.

Found on the stems and underside of leaves of:

I. Exotic plants:
Abutilon, Actinidia deliciosa [kiwifruit], Aralia, Asparagus, Choisya ternata[Mexican orange blossom], Citrus, Cucurbito pepo [marrow], Cycads, Cymbidium [orchid], Eugenia, Hibiscus, Hydrangea, Lagunaria patersonii [Norfolk Island hibiscus], Lavatera, Litchi, Olive, Pear, Rose, Rosemary, Vitis vinifera [grapevine]

II. Native plants:
Avicennia marina [mangrove], Brachyglottis repanda [rangiora], Coprosma repens [taupata], Dichondra repens [mercury bay weed], Entelea arborescens [whau], Hebe elliptica, Hibiscus sp., Myoporum laetum [ngaio], Myrsine australis [mapou], Nestegis lanceolata [white maire], Olearia paniculata [golden akeake], Ozothamnus leptophylla [tauhinu / cassinia], Pittosporum sp., Plagianthus divaricatus [saltmarsh ribbonwood], Pouteria costata [tawapou], Pseudopanax sp., Pteridium esculentum [bracken], Solanum aviculare [poroporo], Vitex lucens [puriri].