Biology

Host range:

The host range of RWA includes more than 140 species of cultivated and wild plants within the family Graminae (grasses). These include wheat, barley, triticale, rye, oats, pasture grasses and wild genera including Poa, Bromus, Hordeum, Lolium, Phalaris and others. Wheat and barley are most susceptible, while triticale, rye and oats are less susceptible. In South Africa, native grasses apparently do not host RWA.

Lifecycle:

In its native range, the annual lifecycle of RWA includes sexual and asexual phases. However, like most other introduced aphid pests in Australia, invasive populations of RWA reproduce asexually with females giving birth to live female offspring.

In autumn, aphids may infest wheat seedlings soon after emergence, usually from wingless aphids walking off nearby senescing hosts. Aphids require actively growing plants for development; populations start to increase from tillering and stem elongation. Aphids regularly move by walking among leaves, tillers and plants, so that the percentage of infested plants increases during the crop cycle. Population growth becomes most rapid from booting onwards. Early in the crop cycle, the vast majority of aphids are wingless. Later in the crop cycle as aphid population density increases, the proportion of winged aphids increases and may reach high levels prior to ripening; at this stage, aphids emigrate in search of alternative summer hosts. Alate RWA are weak flyers, but are thought to travel on wind currents efficiently enough for some aphids to locate isolated host plants.

RWA is able to survive under a wide range of temperatures and may perform better at lower temperatures than the other cereal aphids. However does not do well under higher temperatures (>25°C). Under laboratory conditions, generation time ranges from approx. 20 days at 10°C, and 9 days at 20°C.

Page Last Reviewed: 03 Jun 2016
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