Wheat Stem Sawfly

Cephus cinctus

moderate risk
insect

Overview

A significant pest of wheat throughout the Middle East, Central Asia, and North Africa, where wheat is the primary staple crop. Larvae cut the stem from inside, causing characteristic 'whiteheads' just before harvest — the stem lodges or snaps, making mechanical harvesting impossible and destroying yield.

Adult is a slender black wasp-like insect 8–13 mm with yellow banding on the abdomen. Larvae are pale yellowish-white legless grubs found inside wheat stems.

Prevention Strategies

  • •Use solid-stemmed wheat varieties which physically block larval movement
  • •Early harvesting before larvae complete stem cutting
  • •Crop rotation with non-host legumes or oilseeds
  • •Destroy crop stubble by deep ploughing to kill overwintering larvae
  • •Avoid late seeding which increases crop exposure to peak adult flight

Control Methods

  • •Pyrethroid or organophosphate spray during adult emergence and egg-laying period
  • •Biological control using parasitic wasp Bracon cephi — can achieve 50–90% parasitism
  • •Harvest lowest possible to remove stem-base overwintering larvae
  • •Stubble burning where permitted to reduce next-season population

Interesting Facts

  • •The larvae's stem-cutting behaviour is thought to be an adaptation to prevent parasitoid wasps from entering from above
  • •Solid-stemmed wheat varieties were developed specifically against this pest and can reduce losses by over 90%
  • •A single stem can only contain one larva — the first larva to hatch will kill later arrivals