Pests and Diseases

Various weeds, pests, and diseases can affect Christmas trees’ growth. Growers must be able to identify the most common ones to assess the potential damage that each pest may cause. Use Penn State Extension’s extensive resources to learn about Christmas tree pests and diseases including pine shoot moth, pine sawfly, spruce gall adelgid, conifer seed bug, white pine weevil, and spruce spider mite. Tips on integrated pest management for Christmas tree production are available too.

Common Christmas Tree Diseases

Fungal pathogens and water molds are the primary cause of concern to the Christmas tree industry. Because there are many species grown for the Pennsylvania Christmas tree industry, there are many diseases you may have to manage. Christmas trees extensively grown in Pennsylvania include spruce, pine, and Douglas fir.

Common Christmas tree diseases include:

• Spruce needle rust: Infected trees appear disfigured and have extensive needle discoloration.
• Gall rusts: Damage includes shoot and branch injury.
• Amarillaria root rot: Symptoms include dark fungal rhizomes, resembling shoestrings beneath the bark, on the roots, and in the soil.
• Phytophthora root rot: Signs of this disease include reduced or stunted growth, chlorotic or red-brown needles, needle loss, root decay, bleeding basal cankers, and eventually, the death of the tree.
• Ploioderma needle cast: Symptoms appear in the winter and include yellow spots and bands that give the needles a mottled appearance.
• Red-band needle blight: Initial symptoms include dark green bands on the needles, which are quickly replaced with brown or reddish-brown lesions.
• Pine wilt disease: Pinewood nematodes that spread from infected to healthy pines in the spring cause the needles to turn yellow then reddish-brown.
• White pine blister rust: Caused by a fungus, symptoms include yellow-bordered cankers on the trunk of 3-4-year-old branches.
• Swiss needle cast: Damage includes the dieback of needle tips that resembles drought damage.
• Rhizosphaera needle cast: Damage causes discoloration of needles, and young trees are most susceptible.
• Rhabdocline needle cast: Infection occurs around bud break when buds are opening to expose susceptible immature needles.
• Spruce spider mites: It takes just three weeks for spruce spider mites to develop from an egg to an adult. Damage includes yellow spots, rusty or bronzed needles, and premature needle drop.

Christmas trees are also at risk of environmental damage. Air pollution, in particular, has been shown to affect all conifers.

Christmas Tree Insect Pests

Most Christmas trees are free of insects and other arthropods. However, there may be one or more species lurking within your real Christmas tree.

Common insect pests include:

• European pine shoot moth: The first sign of damage caused by this pest is wilted shoots that soon turn brown.
• Pine sawflies: Symptoms include the complete defoliation or sparse, patchy, missing foliage anywhere on the tree.
• Hemlock woolly adelgid: A severe infestation may result in premature needle drop, reduced twig growth, dieback, or death of the tree.
• Cooley spruce gall adelgid: When an infestation is heavy, the resulting bud destruction may destroy the shape of the tree.
• White pine weevils: Damage includes a typical “shepherd’s crook” wilt.
• Gypsy moths: Damage includes needle discoloration and injury.
• Zimmerman pine moth: Identification is usually through the presence of a popcorn-like pitch mass on the main trunk.
• Japanese beetles: In the late summer to early fall, damage includes seedling discoloration.
• Pine needle scales: This is an armored scale that produces a white, oyster-shell-shaped, wax covering.
• Pine root collar weevil: Because of the damage caused to the root, symptoms include trees loose in the soil, leaning, or dying.
• Pine shoot beetle: Symptoms include boring dust on cut trees or stumps.
• Striped pine scale: Signs of this pest include black sooty mold on the surface of bark and needles.

Christmas Trees Pest and Weed Management

Integrated Pest Management plays a crucial role in any successful Christmas tree production. The basics of an IPM approach include planning and prevention, identification and understanding of pests and problems, monitoring, and control options.

Planning and prevention require an understanding of the possible pests that might affect your Christmas tree crop. Birds, for example, aren’t a huge problem, but they can occasionally damage the tops of taller trees. The same can’t be said of all vertebrate pests.

Being able to identify pests and problems is critical if you want to be able to reduce the risk of tree damage. A good scouting program for all seasons can lead to more accurate pest and disease management.

Pesticide application has a role to play in an Integrated Pest Management plan. However, you have to be wary because chemical damage can occur from pesticide applications made during the growing season.