ABSTRACT
Summary Bluegreen aphid (BGA) (Acyrthosiphon kondoi Shinji), recently arrived in Western Australia, poses a serious threat to 7 million ha of legume-based pastures, 93% of which is sown to subterranean clover (Trifolium subterraneum). Two experiments were conducted in the summer of 1980 to investigate the resistance of commercial cultivars and breeding
106lines to BGA. In the first experiment, 18 commercial subterranean clovers, 3 commercial medics (Medicago spp.), and 1 serradella (Ornithopus compressus) were tested as 7-week-old plants. The second experiment tested a total of 67 selections, breeding lines, and commercial cultivars as seedlings. Plants were grown in aphid-proof cages in controlled environment conditions with 18°/10°C day/night temperatures. Aphids were applied at the beginning of each experiment, and plant damage was monitored at weekly intervals. After 4 weeks, almost 80% of the varieties tested showed damage symptoms ranging from some dead leaves to all dead plants. Symptoms did not develop at the same rate on all varieties. One commercial cultivar and one introduction showed a high level of tolerance to BGA.
