Pasture root aphids

Agronomist, Karl Drever (Davies & Rose Creswick), has reported a severe attack from pasture root aphids (Aploneura lentisci) on a spring-sown perennial ryegrass pasture. Karl says pasture root aphids can be found on nearly all ryegrass plants growing on the heavier black clay soils and the health and persistence of these plants has been badly affected. Interestingly, plants growing on the lighter soil sections within the paddock are growing well and pasture root aphids cannot be found.

Pasture root aphids are recognised as important pasture pests in New Zealand, where they are widespread and have been shown to significantly reduce the growth and survival of ryegrass and tall fescue. The importance of pasture root aphids in Australia has only recently been realised since new grass endophytes have been developed. To date pasture root aphids have been located in New South Wales, Victoria, South Australia and Tasmania.

Symptoms of damage are often associated with poor 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. Adult pasture root aphids are oval bodied insects that grow to approximately 2.5 mm in length. They are usually cream or pale yellow in colour and have very small antennae. They can be confused with the pasture mealybug. Pasture root aphids are most easily detected by the presence of a white fluffy wax that is exuded from their body. To check pastures, use a spade to dig up soil to a depth of approximately 30 cm, and then break up the soil over a plastic sheet. Look for the white waxy exudates and examine this wax for aphids.