Diaspidiotus ostreaeformis (Curtis)
(Sometimes placed in the genus Quadraspidiotus).
Common name: European fruit scale.
Geographic distribution: Cosmopolitan, widely distributed in the Palearctic region. CAB International 2002, Distribution Maps of Pests, #636.
Host plants: Polyphagous, especially deciduous Rosaceous trees.
Morphology: The dorsal macroducts are one-barred. Female body yellow, about 1.4 mm long, pear-shaped, pygidium with two convergent lobes, second lobe with an external notch; the third lobe a small round projection. One pair of paraphyses places between the median and second lobes, another near the reduced third lobe. With 2-3 broad, fimbriate plates placed beyond the third lobe. The anus is located between the median lobes and the vulva. The Perivulvar pores in five groups. The female shield](entry/Shield) is circular, slightly convex, grey-brown, 1.5-1.9 mm in diameter, margins sometimes paler. The juveniles exuviae are brighter, slightly off-centre. The shield of the male is grey, elongated, bearing at one end the exuvium of the crawler.
Life history: The European fruit scale is univoltine. During winter the second-stage nymph are in diapause till spring. They then molt and mate, and females lay eggs (60-160/female). The emerging crawlers infest mostly tree bark, stems and branches and sometimes early fruits.
Economic importance: Economic losses due to D. ostreaeformis on different fruit tree crops are difficult to assess. Heavy infestations may cause branches to die, the trees to lose vigour, and to curtain their productive lives. In addition, scale infestation of fruits results in red spots.
Monitoring: Weekly examinations of bark for scales in the spring, and presence of red spots on fruits (which may also be due to Q. perniciosus or to Parlatoria oleae. Recording crawlers on sticky bands wrapped around tree branches.
crawlers on shelter trees as large as the birches and alders in these trials would present a major hazard to adjacent orchards
Horticultural control: Avoiding susceptible trees in shelter belts around orchards. Conifers and Carpinus betulus L. appear to be resistant to the pest, thus more suitable.
Chemical control: Oil treatments in spring, used against other overwintering pests, may also reduce scale numbers. Spring sprays with mineral oils and an insect growth regulator, or with an organophosphate were effective.
Biological control: Several aphelinids, such as the ectoparasitoid Aphytis spp., and the endoparasitoid Encarsia spp., along with predatory Coccinellidae usually control the pest. However, the use of pesticides against other pests may kill these enemies and result in European fruit scale outbreaks. The entomopathogenic fungus Fusarium larvarum Fuckel occurs on the pest in Hungary.
Hippe, C., Schwaller, F., Mani, E., Kull, H. and Kozár, F. 1995 Bekampfung einheimischer Austernschildlause. [Control of native oyster scale insects]. Obst- und Weinbau 131: 84-85.
Hornok, L. and Kozár, F. 1984 Fungi associated with a scale insect, Quadraspidiotus ostreaeformis (Curtis, 1843) (Homoptera, Coccoidea: Diaspididae). Acta Phytopathologica Academiae Scientiarum Hungaricae 19: 9-11.
McLaren, G.F. 1989 Control of oystershell scale Quadraspidiotus ostreaeformis (Curtis) on apples in Central Otago. New Zealand Journal of Crop and Horticultural Science 17: 221–227.
Wearing, C.H. and Colhoun, K. 2011. Observations on the host plants of oystershell scale (Diaspidiotus ostreaeformis: Hemiptera: Diaspididae). New Zealand Journal of Crop and Horticultural Science 39: 71-76.