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A. kondoi feeds on the stems and leaves of its host plants. Infestation of lucerne can reduce overall plant height and leaf area. The smaller leaves are sometimes twisted or yellowed, internode lengths are shortened, while premature leaf fall can occur. The stunting of plants is similar to that resulting from cold weather, and occurs when aphids feed on seedlings or regrowth after cutting. Dry weight yield is reduced, even with moderate aphid infestations.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
Since its introduction into the USA, Australia and New Zealand, from the mid-1970s, A. kondoi has become a major pest of lucerne in these countries. It has, for example, now spread throughout the lucerne growing regions of the USA, where it is an early and late season pest (Stoetzel, 1990). It is far more damaging to lucerne than the related pea aphid, Acyrthosiphon pisum.
A. kondoi can cause severe economic damage at even low population densities, and lucerne production can be affected before visual signs of damage are obvious. It can cause plant death, for example, when infesting seedling stands. Moderate levels of infestation on mature perennial lucerne can stunt stems, cause leaf yellowing and sometimes premature leaf fall, and reduce root reserves. The damage done by aphids can have a carry over effect and reduce the yield of at least two subsequent crops. The damage is most severe when aphids attack the new regrowth following winter cutting. As plants mature they become more tolerant of aphid attack.
The reduction of lucerne yield by A. kondoi in Japan was reported to be as high as 40-70% by Takahashi (1997). Yield losses in New Zealand are in the order of 62, 30 and 71%, in spring, summer and autumn, respectively (Brieze-Stegeman, 1979). Bishop (1984) reported yield reductions ranging from 10 to 18% of dry matter in winter and early spring harvests of lucerne in New South Wales; as a result of autumn damage by A. kondoi being carried over into the later harvests. In Australia and New Zealand, lucerne produces green feed in summer and autumn, which permits the fattening of young sheep or cattle for lucrative markets; lucerne can also be used for good quality hay. In these countries, A. kondoi is one of the aphid species implicated in pasture deterioration.
The production of honeydew by A. kondoi contributes to economic damage, as the honeydew encourages the growth of sooty moulds and other diseases. The damage due to direct feeding may also be exacerbated by viruses spread by the aphid. A. kondoi is a vector, in a non-persistent manner, of Alfalfa mosaic virus, Lucerne Australian latent virus and Lucerne transient streak virus in lucerne crops. It has also transmitted, at low levels, watermelon mosaic viruses to squash, cantaloupe, watermelon and pumpkin under greenhouse conditions in California (Wyman, 1979); and Cucumber mosaic virus and Bean yellow mosaic virus in lupins in Australia (Jones, 1993; Bwye et al., 1995; Jones et al., 2003). A. kondoi has been implicated as a potential vector of Bean leafroll virus (BLRV) as it was observed colonising lucerne plants adjacent to subterranean clover (Trifolium subterraneum) seed production paddocks infected with BLRV. It was subsequently shown in a glasshouse trial to transmit BLRV from an infected lucerne plant to subterranean clover in a persistent manner (Peck et al., 2012).
A. kondoi is also an economic pest of clover and other leguminous pasture grasses. It reduces dry-matter yield, and transmits viruses in clover (Trifolium spp.). Seed production in white clover can be reduced by up to 38% as a result of A. kondoi infestations (Brieze-Stegeman, 1979).