Yellow-Headed Spruce Sawfly

The larvae of this insect look like a caterpillar. They eat the needles of Spruce causing damage. They have yellowish bodies and yellow/brown heads. The new needles are attacked first. They are chewed down almost to the base before the insect moves on to older needles. A severe infestation, lasting for 3 or more years can kill a tree due to the foliage loss and lack of photosynthetic energy being created.

Tree Damage

  • Needles are chewed by the larvae. Usually starting on the lower limbs of the tree around the end of June or early July in Calgary.
  • The youngest needles (at the tips of branches) are generally attacked first before the insect moves on to the older growth.
  • Trees with an infestation over a period of 2 or more years will show obvious defoliation.

Control Measures

  • Inspect trees annually for signs of damage or larvae.
  • It is possible to remove the larvae by hand if it’s a low level infestation.
  • A high-pressure spray of water will effectively remove most of the larvae.
  • A professional pesticide applicator can apply the high pressure water or a mild pesticide on large scale infestations or when the scope is beyond your means.