Constraint – Webworm


  • Larvae are brown/black with a maximum length of about 18 mm

  • Pupae are 12 mm long, honey brown, and found underground  

  • Adults are long legged grey-brown moths with a wingspan of about 22 mm


  • Small bare areas appear in the crop usually within three weeks of plant emergence

  • Larvae feed on the upper surface of the leaf blades, resulting in "windows" in the leaf

  • Feeding generally occurs in the centre of the leaf but may also occur on the margins

  • Older larvae sever the leaf blades and occasionally whole plants at ground level


  • Damage occurs in winter-spring, yield penalty can occur if populations are not controlled


Spot spraying of damaged patches is possible within crops. A buffer zone of 20 m around the infestation should also be sprayed. Prolonging the period between paddock preparation and sowing, as well as shortening pasture phases can help to deter egg laying females.

Links and Resources

Insectopedia - Webworm

Description, biology, damage, monitoring, sampling, and control methods.Published 2000.

SARDI - Webworm

3 page PDF. Identification, damage, lifecycle, and control methods. Last updated 1999.