How to Treat Mites on Norway Spruce Trees

Overview

Spider mite infestations can cause your Norway spruce trees' needles to become mottled and discolored, turning them from yellow to bronze before they drop prematurely. Norway spruces can also suffer from twig dieback and even death from heavy infestations. Spruce spider mites (Oligonychus ununguis) are most active during the cooler spring and fall months, with females laying their eggs during winter on the bark and needles, and then hatching in April or May. The adult mites are extremely tiny, only ½ millimeter long, and are dark green with eight legs. Fortunately, it's not difficult to treat them.

Step 1

Feed your Norway spruce trees with a low-nitrogen tree fertilizer according to the dosage instructions on the label to strengthen the tree's ability to endure the damage from the infestation. Water your trees deeply to soak the soil down around the root area once each week when rainfall is less than 1 inch.

Step 2

Spray the infested trees with a miticide, such as clofentazine, bifenazate or hexygon, or horticultural oil during the growing season. Also spray the trees with a pyrethroid miticide in early autumn or fall.

Step 3

Spray the spruces with dormant horticultural oils in winter to kill the overwintering eggs and adult spider mites. Apply the dormant oil only if the infestation was heavy in the fall.

Step 4

Plant flowers around and nearby the Norway spruce tree to attract natural predators of spider mites, which include lacewings, minute pirate bugs, lady beetles, predatory midges and rove beetles.

Tips and Warnings

  • Always follow the instructions on the miticide or horticultural oil label exactly. Wear gloves and eye protection when you're applying these chemicals.

Things You'll Need

  • Low-nitrogen tree fertilizer
  • Garden hose
  • Miticide or horticultural oil
  • Dormant horticultural oil
  • Flowers or flowering plants

References

  • University of Minnesota Department of Entomology: Spruce Spider Mite
  • Rainbow Treecare: Spruce Spider Mite

Who Can Help

  • Virginia Department of Forestry: Tree Disease and Insect Guide for Conifers--Spruces
Keywords: Spruce spider mites, treat Norway spruce mite, get rid of spider mites

About this Author

Sarah Terry brings 10 years of experience writing novels, business-to-business newsletters, and a plethora of how-to articles. Terry has written articles and publications for a wide range of markets and subject matters, including Medicine & Health, Eli Financial, Dartnell Publications and Eli Journals.