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Lucerne flea

Lucerne flea (Sminthurus viridis) hatch following periods of good soaking autumn-winter rainfall and can cause significant damage to emerging crops and pastures at this time of year. This season, hatchings have been somewhat delayed although they now appear to be hatching in some regions. Consultant, Glen Smith (3D-Ag) has reported lucerne flea in several paddocks of canola (cotyledon – 1-leaf stage) around Wagga Wagga, in the South West Slopes district of New South Wales. Glen says lucerne flea are patchily distributed on plants and damage is limited to minor ‘windowing’ of the leaf surface. The canola seed was treated with imidacloprid, and this may be offering some level of protection. Glen will monitor canola paddocks closely over the next few weeks to see if nymphs begin appearing – indicating a possible rise in population density, and if damage to cotyledons or younger leaves increases. Philip Jobling (cesar) has recently observed a low number of lucerne flea in several lucerne paddocks near Werribee, in the Central district of Victoria.

Lucerne fleas are generally 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 flea has 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 fleas into the crop from neighbouring paddocks. As lucerne fleas are often distributed patchily within crops, spot spraying is generally all that is required.

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