Arborvitae Pests

Save

Arborvitae (Thuja occidentalis) trees are popular throughout the northern United States and Canada. Arborvitae, an evergreen, has soft scale-like leaves that form flat sprays, rather than prickly needles many associate with evergreens. It maintains its shape naturally without pruning. These characteristics make it a favorite among landscapers and gardeners. Unfortunately, arborvitae is also popular with many destructive insects.

Bagworm

  • Bagworms (Thyridopteryx ephemeraeformis) infest arborvitae May through the middle of June. These pests are identified through their larvae's silken bags that hang from branches. Infused with plant material, the bags are often mistaken as part of the plant. At maturity, the bags can reach 1 inch long. Females will remain in the bag their entire lives, while males will emerge as a black moth with clear wings. Check for and destroy bags throughout the year. Pesticides can be effective when bags are small, although a second application is advised two weeks after initial spray.

Arborvitae Leafminer

  • Arborvitae leafminer (Thyridopteryx ephemeraeformis) is a silver-gray moth, generally 1/3 inch long. Signs of an infestation include yellow or brown tips on foliage, especially on the south side of the plant. Larvae feed on the tips of arborvitae through the spring and emerge as adults in June and July. Remove tips by hand for light infestations; spray with a systemic insecticide in late fall or early spring for heavy infestations.

Strawberry Root Weevil

  • The strawberry root weevil (Otiorhynchus ovatus) prefers arborvitae over other evergreens. Wilting and dieback of branches are common symptoms of an infestation. Since the adults feed near leaf margins, notching also indicates weevils. To kill adult beetles before they lay eggs, apply foliar insecticides in July. Larvae overwinter in the soil and feed on roots, and the fungi Beauveria bassiana and entomophagous nematodes are effective controls when applied to the soil in early August. The University of Minnesota Entomology department recommends keeping soil moist to ensure effectiveness.

Fletcher Scale

  • Though arborvitae is not a favorite of fletcher scale (Parthenolecanium fletcheri), it can fall victim to this pest. Signs of an infestation include yellowing needles, premature needle drop and a black sooty mold growth. Eggs hatch mid to late June, although the round, brown adult females may arrive as early as April, often clustering where leaves join branches. Use horticultural oil to smother exposed eggs, and dormant young adults. Systemic insecticides also protect arborvitae.

Spruce Spider Mite

  • Spruce spider mites (Oligonychus ununguis) may be difficult to see with the naked eye, but their effects are clear. Yellow or bronze leaves, foliage drop and branch dieback are symptoms of an infestation. A sheet of paper held under a branch while shaken will confirm spider mites. A dormant oil spray in the fall will remove mites without damaging their natural predators.

References

  • Photo Credit Thinkstock/Comstock/Getty Images
Promoted By Zergnet

Comments

Resources

You May Also Like

  • Spider Mites on Evergreen Trees

    Spider mites can infest a variety of different plants and trees. A spider mite infestation can be devastating and evergreen trees are...

  • Do Spider Mites Kill Arborvitaes?

    The arborvitae is an evergreen that can be grown as tree or a shrub. It typically has a conical or cylindrical shape....

  • How to Identify Small Tiny White Flying Insects

    If you've noticed tiny white flying bugs around your home, chances are these are whiteflies. There are other tiny white insects such...

  • How to Care for Arborvitae

    Arborvitae is a popular landscaping shrub that is often used around foundations and along fence rows. Native to North America and Asia,...

  • The Care of Rheingold Arborvitae

    Arborvitae (Thuja occidentalis) is a group of evergreen plants that includes a variety of cultivars. Rheingold is a variety that grows to...

  • How to Get Rid of Bagworms on Arborvitae Trees

    The bagworm is a caterpillar that builds a bag out of plant material. The female lives her entire life in the bag,...

  • Why Do My Arborvitae Turn Brown?

    Browning during winter is normal for American arborvitae (Thuja occidentalis), but browning at other times of year could be a sign of...

  • Bugs That Eat Tree Leaves

    Homeowners often notice their trees are under attack from defoliating insects. Many caterpillars, mites and beetles feed on the foliage of trees....

  • Black Leaves on Arborvitae

    Arborvitae are blue-green cypress trees or shrubs sometimes grown as privacy screens because of their broad, spreading branches and evergreen foliage. When...

  • Problems With Arborvitae

    Arborvitae, also called thuja, are evergreen trees with flat, scale-like shoots and shaggy, reddish-brown bark. They grow from 10 to 60 feet...

Related Searches

Check It Out

How to Make a Vertical Clay Pot Garden

M
Is DIY in your DNA? Become part of our maker community.
Submit Your Work!