Spruce spider mites thrive during the cooler temperatures in spring and fall.
What species of trees can be infected?
They range in color from green to orange-red and attack more than 40 species of conifers, including:
- Arborvitae
- Fir
- Hemlock
- Juniper
- Spruce (specifically dwarf Alberta spruce)
How do spider mites affect my trees?
Spruce spider mites feed on the sap from tree needles. Flecking and yellowing may occur near the feeding sites. Intense feeding may cause browning and premature needle drop. Silk webbing and cast skins from previous molts may indicate increasing infestation.
Intense feeding may cause browning and premature needle drop. A continued infestation may result in death of the branch and possibly lead to tree death.
Solutions and Treatment
You can help to curb spruce spider mite populations in the fall and reduce the number of eggs that spread in the winter. Appropriate treatments include miticides or dormant oil, specifically in the north. Horticultural oil may be damaging to some plants such as dwarf Alberta spruce and Colorado blue spruce, so an alternative treatment would be necessary.