Farmer Guides

Pests and Diseases

A Guide to Willow Sawfly

  • The Willow sawfly is found throughout New Zealand
  • Their  larvae feed exclusively on willows with all varieties being susceptible
  • Emerging larvae eat a ‘window’ in the leaf, and then feeds along the edge of the hole. After moulting it usually moves to the edge of the leaf, and continues to feed.
  • Damage from willow sawfly is serious but periodic and the future risk is considered low

NZ Poplar & Willow Research Trust: http://www.poplarandwillow.org.nz/library/willow-sawfly-nematus-oligospilus

The Giant Willow Aphid

  • This very large aphid appears as colonies in summer
  • By late summer there may be tens of thousands on a single tree
  • It has an adverse impact on tree growth, exacerbates the effects of droughts and the honeydew they produce attracts wasps
  • Control with systemic pesticides is possible
  • Biological control agents are being sought

NZ Poplar & Willow Research Trust: http://www.poplarandwillow.org.nz/library/giant-willow-aphid