Lucerne flea

Agronomist, Allan Edis (Landmark), has reported lucerne flea (Sminthurus viridis) causing damage to an established lucerne stand near Temora, in the South West Slopes district of New South Wales. The paddock was sprayed with an organophosphate in July and provided good control of lucerne flea. However, lucerne flea numbers have rebounded and have now built up to a large population size.

District agronomist, Philip Bowden (NSW DPI), has also reported lucerne flea damage near Cootamundra, in the South West Slopes district of New South Wales. Philip says there has been some isolated damage caused by lucerne flea to several newly-sown lucerne paddocks.

Lucerne fleas move up plants from ground level, eating tissue from the underside of foliage. They consume the succulent green cells of leaves through a rasping process, avoiding the more fibrous veins and leaving behind a layer of leaf membrane. This makes the characteristic small, clean holes in leaves, which can appear as numerous small ‘windows’. In severe infestations this damage can stunt or kill plant seedlings. Adult lucerne fleas are approximately 3 mm in size. They are green to the naked eye, although their globular abdomens are a green-yellow colour that often has a mottled pattern of darker pigments. Click here for images of the lucerne flea.

Lucerne flea are typically a problem in regions with loam/clay soils. Paddocks are most likely to have problems where they follow a weed infested crop or a pasture in which lucerne fleas have not been controlled. If chemical control is required, do not use synthetic pyrethroids. In paddocks where damage is likely, a border spray may be sufficient to prevent movement of lucerne flea into the crop from neighbouring paddocks. As lucerne fleas are often distributed patchily within crops, spot spraying is generally all that is required. Grazing lucerne and pasture paddocks before spraying is recommended as this will help open up the canopy to ensure adequate spray coverage.