Hosny, M.M., Amin, A.H., & El-Saadany, G.B. 1972 The damage threshold of the red scale, Aonidiella aurantii (Maskell) infesting mandarin trees in Egypt.. Zeitschrift für Angewandte Entomologie 71: 286-296.

Notes: Threshold lies at 0.24 live females per leaf in June.