Lucerne flea

Although an important pest at crop establishment in autumn and early winter, lucerne flea (Sminthurus viridis) can also be a major problem at this time of year. Agronomist, Ron Saunders (Landmark), has reported high numbers of lucerne flea in various irrigated clover paddocks near Kerang, in the Wimmera district of Victoria.

The lucerne flea has been a major pest problem in the Wimmera for the last few seasons, affecting mostly pulses and cereals. Lucerne flea also caused major damage in many parts of the Wimmera earlier this year, attacking canola, cereals, pulses and pastures.

The lucerne flea is up to 3mm long as adults and ‘spring’ off vegetation when disturbed. The pests work up the plants from ground level, eating tissue from the underside of the foliage. They leave distinctive feeding damage of "windows" of transparent leaf membrane. Crops are most likely to have problems where they follow a weed infested crop or a pasture in which lucerne flea has not been controlled.

Despite the high tolerance to many synthetic pyrethroids and the potential problems of spraying these chemicals for the control of the lucerne flea, the continued use of any chemical class (e.g. organophosphates) could lead to resistance problems. Consider rotating control strategies, employing both chemical and non-chemical control.

Snout mites (which have orange bodies and legs) are effective predators of lucerne fleas, particularly in pastures, where they can prevent outbreaks. The complex of beneficial species (including snout mites) should be assessed before deciding on control options. Implement control in the season prior to sowing to minimise numbers, or plant crops less susceptible to lucerne flea damage; avoid pastures with high clover content, lucerne and cereal crops, which are preferred hosts of the lucerne flea.