Pasture root aphids

Territory manager, Blair McCormick (Agricom), says pasture root aphids have been found in a perennial ryegrass paddock near Terang, in the Western district of Victoria. Signs of feeding damage are noticeable, and likely to be exacerbated by the moisture-stress these plants are experiencing. Business development manager, Robert Salmon (PGG Wrightson Seeds), reported pasture root aphids in a trial site near Ballarat, in the Western district of Victoria and a perennial ryegrass paddock south of Sale, in the West & South Gippsland district of Victoria. Pasture root aphids were also recently observed in a pasture paddock near Armidale, in the Northern Tablelands district of New South Wales.

There is very little known about pasture root aphids (Aploneura lentisci) in Australia. They are recognised as an important pasture pest in New Zealand, where they are widespread and have been shown to significantly reduce the growth and survival of ryegrass and tall fescue. To date pasture root aphids have been located in New South Wales, Victoria, South Australia and Tasmania. Adults are oval bodied insects that grow to approximately 2.5 mm in length. They are usually cream or pale yellow in colour. They are most easily detected by the presence of a white fluffy wax that is exuded from their body.

As the name suggests, pasture root aphids live underground on plant roots, and colonies can develop anywhere in the root system from the crown to deep within the soil profile. They cause damage by sucking sap from the plant tissues, which weakens the plant. Feeding can gradually thin pastures, and the effects are amplified when plants are stressed by other factors such as drought, heavy grazing or attack from other insects. It has been reported that pasture root aphids can also damage wheat.

Symptoms of damage are often associated with disappointing pasture recovery after drought, a loss of vigour and poor persistence. Within a drill row, individual plants hosting high levels of root aphid will often be small, weak, pale and carry dead material around their base. Insecticide applications are largely ineffective against root aphids due to their subterranean habits. The use of grass endophytes is likely to be the most effective control strategy.