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Saissetia coffeae (Walker)

Hemispherical scale
[Saissetia coffeae]. L: immature and young adult females. R: mature female.

[Saissetia coffeae]. L: immature and young adult females. R: mature female.

Walker named this species coffeae in 1852, presumably because it was first found on coffee bushes. Although it has ridges on the top shaped like an "H" when immature (see Saissetia oleae, olive scale), it becomes smooth when adult.

Status in New Zealand: an exotic (adventive) species, first recorded here in 1879. Hemispherical scale is an important pest of ornamentals and potted plants, especially ferns. It is recorded on 18 exotic plants and 14 native plants here, and has been found inside native forest. Its range is throughout the North Island and most of the South Island.

Biology: overlapping generations per year in New Zealand, usually overwintering as immature females. As the female lays her eggs, her body mass shrinks, forming a brood chamber underneath where the eggs hatch into a mass of pinkish-coloured crawlers. Hemispherical scale is parthenogenetic and there are no males.

Found on the stems and underside of leaves of:

I. Exotic plants:
Alternanthera phylloxeroides
[alligator weed], 'Asparagus fern', Citrus, Cornus alternifolia [pagoda dogwood], Cydonia oblonga[quince], Dendrobium noble [orchid], Fatsia japonica, 'ferns', Gardenia, Homocladium sp., Luculia sp., Picea pungens cv. Glauca [blue colorado spruce], Prunus persica var. nucipersica [nectarine], Prunus salicina [japanese plum], Saintpaulia [African violet], Thunbergia [black-eyed susan], Vitis vinifera [grapevine], Washingtonia robusta [washington palm]

II. Native plants:
Asplenium bulbiferum, Asplenium pauperequitum, Asplenium sp., Avicennia marina [mangrove], Blechnum fraseri [ra], Coprosma ?propinqua, Cordyline australis [tī / cabbage tree], Geniostoma sp., Hebe macrocarpa, Myoporum laetum [ngaio], Parahebe lyalli, Pouteria costata [tawapou], Pratia physaloides, Pteridium esculentum [bracken]