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:

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:

Poplar Sawfly Cladius grandis

  • A single poplar sawfly, Cladius grandis (Tenthredinidae), larva was detected in a gypsy moth trap in Dunedin in February 2019
  • Adults: 6-9mm; overall reddish yellow, head and part of thorax black; wings yellowish hyaline strongly iridescent, venation reddish yellow
  • Larvae: up to 16mm; overall yellow with two lateral rows of black spots (dorsal much larger than ventral) and whitish hairs; head blackish and brownish except some yellow spots on the frontal part
  • Host plants include species from Family Salicaceae: Populus alba, P. balsamifera, P. canadensis, P. dilatata, P. monilifera, P. nigra, P. tremula, P. pyramidalis, Salix caprea (pussy willow).

Otago Regional Council: