Since 1990 farmers in the Western Australian wheatbelt have been reporting doublegee plants that appear to be diseased, stunted and producing poorly formed fruit (the spiny casing around the single doublegee seed). Often no obvious cause of this decline in plant health is apparent. Experiments carried out in 1990 showed that an aphid, which feeds hidden in the growing tips of doublegee stems and in young distorted leaves, is the most likely cause. This North American aphid, the dock aphid (Brachycaudus rumexicolens), arrived in WA in 1987. It appears to only feed on docks, doublegees and related plants and is not known as a pest of crops. Infested doublegee plants produce small seeds that have low viability and almost no dormancy. The aphid's presence will contribute to the biological control of docks and doublegees.
Scott, John; Berlandier, Francoise; and Hollis, Kristy
"Biological control of doublegee : Doublegee decline and the dock aphid,"
Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 35
, Article 5.
Available at: http://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol35/iss2/5