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Lucerne flea

Lucerne fleas have been active for many weeks in some localities that received significant rainfall in early-mid autumn. Recently however, widespread hatchings have occurred across several parts of Victoria and New South Wales. Agronomist, Allan Edis (Landmark), reports that lucerne fleas are now present across numerous paddocks south of Temora, in the South West Slopes district of New South Wales. Allan says moderately high numbers have been observed in lucerne and clover paddocks, with obvious signs of feeding damage present. The majority of paddocks have clay-loam soils. Young lucerne flea have been identified from several paddocks near Cootamundra, also in the South West Slopes district of New South Wales.

In Victoria, Garry McDonald (cesar), has confirmed hatchings of lucerne flea near Werribee and Whittlesea, in the Central district, near Harcourt and Maryborough, in the North Central district, and around Ballarat, in the Western district. Agronomist, Greg Toomey (Landmark), has also reported lucerne flea causing damage to an emerging canola crop south of Elmore, in the Northern Country district of Victoria. Despite having an insecticide seed treatment, Greg says feeding damage, characterised by transparent ‘windows’ on the leaf surface, is quite noticeable.

Lucerne fleas (Sminthurus viridis) hatch from their summer diapause following periods of good soaking autumn-winter rainfall. They cause significant damage to emerging crops and pastures at this time of year. Lucerne flea can also cause considerable damage to older crops if numbers build up under favourable conditions throughout the season. 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 pasture in which lucerne flea has not been controlled.

Adult lucerne fleas are approximately 3 mm in length and appear yellow-green to the naked eye, although their globular abdomens are often a mottled pattern of darker pigments. Lucerne fleas ‘spring-off’ vegetation when disturbed. They have a wide host range and will attack most broad-acre crops, including canola, lucerne, pastures, cereals and some pulses.

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 (rather than spraying the entire paddock) is often all that is required.

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