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Small lucerne weevil

Adult small lucerne weevils (Atrichonotus taeniatulus) have been identified for agronomist, Roger Garnsey (Roger Garnsey Agronomy), from an established lucerne paddock near Yass, in the Southern Tablelands district of New South Wales. This weevil is known to attack lucerne, pasture legumes, canola and some weeds, and in New South Wales are regarded as a minor, irregular pest. 

Adult small lucerne weevils are grey in colour with some brownish mottling, and are up to 10 mm long. During the day they typically hide in the soil around the base of plants, though some may be found resting together in groups of 3-4 on a single leaf. The larvae are creamy white, legless grubs, up to 8 mm long, with small, pointed, brown jaws. Click here for images of the small lucerne weevil.

Infestations of small lucerne weevils spread slowly because they do not fly; they have to walk or be carried to spread through a paddock. Young larvae become active in spring and feed on plant roots until mid-January. Adults emerge from the soil from mid-February to March. Eggs are laid at the base of plants, and after hatching in winter, larvae burrow into the soil and begin feeding on roots.  

Large numbers of adults can cause serious damage to subterranean clover pastures by chewing off cotyledons soon after germination. However, they are most damaging to Lucerne, where adults feeding on leaves can defoliate plants. Serious damage also occurs when larvae burrow into or chew furrows in the taproot. Eventually plants die, resulting in lucerne stands with dead patches that increase in size each year as the infestation spreads. Wilting and plant death is most noticeable in summer when larvae are nearly full-grown.

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