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Lucerne flea

Agronomist, Simon Mock (Clovercrest Consulting), has observed lucerne flea (Sminthurus viridis) in medic pastures near Nhill, in the Wimmera district of Victoria. Although the lucerne fleas are only nymphs and the numbers are relatively low at this stage, there is evidence of feeding damage to the emerging seedlings. Agronomist, Kate McCormick (John Stuchbery and Associates), has also reported very high numbers of lucerne flea in two canola paddocks near Horsham, in the Wimmera district of Victoria. Kate says around 30 lucerne flea can be seen per plant in some patches of the paddocks, which have experienced significant feeding damage.

Lucerne flea has been a major pest problem in the Wimmera for the last few seasons, particularly in paddocks with heavier soil types.

Lucerne flea hatch following periods of good soaking autumn or winter rains. Due to the requirements of their eggs, they are generally a problem in regions with loam/clay soils. Keep a good look out in paddocks, particularly with seedling canola, lupins and clover. Lucerne fleas are 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. Consider implementing control in the season prior to sowing to minimise numbers. In crops, spot spraying is generally all that is required; do not blanket spray unless the infestation warrants it. If spraying is required, do not use synthetic pyrethroids. Both Simon and Kate are recommending dimethoate to control these outbreaks.

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.

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