Fig. 1. Percentage survival (mean ± S.E.M.; N=100) of first instar and newly moulted pre-reproductive S. avenae reared at 10°C, 72 h after direct exposure to a range of sub-zero temperatures. Discriminating temperatures for first instar nymphs and newly moulted adult aphids were determined as –11.5°C and –12.0°C, respectively. Means with the same letter are not significantly different at P<0.05 (Tukey multiple comparison test).