Thermal requirements of Aphelinus albipodus (Hayat and Fatima) (Hym, Aphelinidae) on Diuraphis noxia (Mordwilko) (Hom, Aphididae) hosts

The thermal requirements, t and K, and upper developmental thresholds for three developmental periods in Aphelinus albipodus, a parasite imported to the USA for biological control of Diuraphis noxia, were investigated under laboratory conditions. Studies were conducted at constant temperatures in the range 10.0-29.4 degrees C, 14 L:10D photoperiod, and 50-70% R.H. Total developmental time (from egg to adult) in A. albipodus increased from 10.1 days at 29.4 degrees C to 27.9 days at 15.5 degrees C. Adult parasites did not emerge from mummies at 10 degrees C (although pharate adults were recovered by dissection). The thermal requirements for the egg-mummy, mummy-adult, and egg-adult developmental periods were estimated, respectively, as r = 7.62, 9.15, and 8.56 degrees C, and K = 100.30, 107.31, and 208.24 degree-days. The upper developmental threshold was considered to be above 29.4 degrees C because development did not cease and did not appear to be affected by that temperature. The possibility of hibernal dormancy or diapause as well as the potential for successful establishment in California, USA, in A. albipodus are discussed.