New Russian wheat aphid biotype highlights growing resistance concerns

Russian wheat aphid is showing increased cultivar and pesticide resistance, according to entomologist Dr. Astrid Jankielsohn of the Agricultural Research Council. She has identified a new biotype, bringing to five the Russian wheat aphid biotype highlights growing resistance concerns number seen in South Africa. Sabrina Dean reports.

- Sabrina

The Russian wheat aphid (Diuraphis noxia) occurs worldwide where wheat is produced at a commercial scale. South Africa currently has five biotypes affecting production, one of which was recorded for the first time in 2018. It was identified by Dr Astrid Jankielsohn, an insect ecologist at the Agricultural Research Council’s Small Grains Institute in Bethlehem in the Free State.

The Russian wheat aphid (RWA is native to south-western Asia and was introduced into many European countries in the 20th century. It was first noted as a pest in the Crimea in 1901, hence the common name.

The aphid, which is up to 2mm long, is light green in color and has a tiny spike at the rear above its tail, giving the impression of two tails.

The insect feeds on leaves, causing them to turn white and curl up. The main damage, however, is done by the saliva of this pest, which is toxic and stunts growth. Research has also found that aphid infestation affects the flour made from infested wheat plants.

The Food and Agriculture Organization of the United Nations regards RWA as a serious threat to dryland wheat in many developing countries beset by sporadic drought. In Europe, Africa, Asia, and North and South America, RWA has caused crop losses of up to 80%.

CONTROL MEASURES

According to Jankielsohn, much effort is being invested in developing control strategies. The two most widely used of these are chemical control measures and breeding for resistance, but both have drawbacks.