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Weed web moths

We have identified weed web moth (Achyra affinitalis) caterpillars for agronomist, James Christie (JSA Independent), who reports finding low numbers in crops west of St. Arnuad, in the Wimmera district of Victoria. Some leaf chewing damage was evident in one canola crop and one faba bean crop, however James says the numbers of caterpillars were quite low and control is not required.

Weed web moth caterpillars are grey-green and pale brown in colour, with a distinctive black head and grow up to 15 mm long. Caterpillars feed on broad-leaved weeds and a range of crops including canola, lucerne and several pulses. They tend to wriggle violently or crawl around rapidly when disturbed.  Weed web moths are usually most abundant in warmer weather and populations can build up where there is an abundance of green plant material over spring and summer. We have not previously received any reports of this species causing serious damage to grain pods in canola or pulse crops in spring.

For further information about weed web moths, refer to PestFacts Issue No. 4.


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