What is it?
The yellow-headed spruce sawfly is a native North American insect with a distinctive dark yellow head. It attacks spruce trees, consuming new and then old needles, which can cause severe defoliation and death.
Symptoms
- Defoliation starts from the top of the tree and moves downward.
- Yellow-headed caterpillar like insects can be found in between needles.
- The insects will eat new needles first, then moves to old needles.
Damages
- It will cause complete defoliation and deform the tree.
- One year of severe defoliation can lead to reduced shoot growth. Two or more years of defoliation can lead to dead branches, a dead top, and tree death.
What to do?
- Check your trees regularly for any damage or larvae.
- Hand pick and destroy the larvae if the population is small.
- Using high-pressure water is an effective, non-chemical method for removing the larvae.
- Pruning can helps surviving spruce trees reshape the crown and encourage new growth.
- Insecticide can be applied in mid-late June to protect larger spruce trees under attack.
Other resources:
https://www.calgary.ca/parks/pests/yellow-headed-spruce-sawfly.html