A new bluegreen aphid biotype (BGA, Acyrthosiphon kondoi Shinji) has been found in south-eastern Australia that causes severe damage and mortality in seedlings of previously resistant pasture legume cultivars. Populations of BGA collected at Urrbrae and Binnum, SA in 2009 caused 100% mortality in 29 cultivars of annual and perennial Medicago spp. and annual Trifolium spp. Delaying inoculation from the first trifoliate to the 6–8 trifoliate stage and removing susceptible genotypes from experiments had no impact on reducing mortality from 100% in previously resistant barrel medics. A half-sib family of lucerne from the SARDI breeding program has maintained resistance to the Urrbrae 2009 BGA.
A detailed study of the virulence of BGA populations collected from Toowoomba (Qld), Tamworth, Howlong (NSW), Launceston (Tas.), Colebatch, Kimba, Urrbrae and Vivonne Bay (SA) in 2010–11 on 33 pasture legumes provides evidence of new virulent BGA being widespread, despite these populations causing less severe damage and mortality than the two populations collected in 2009.