Moth damage in trees occurs in a different manner than damage from borers and bark beetles. Moths focus their energy on defoliation, which means they consume their target’s leaves/needles. This inhibits the tree’s ability to photosynthesize (produce food) and weakens the tree over time. Stress caused by this increases susceptibility to other diseases and pests.
Moths have four stages to their life cycle:
- Egg
- Larva (Caterpillar)
- Pupa
- Adult Moth
Moth life cycles range from one generation per year to one generation every 2 years in the case of the Spruce Budworm.
Table of Contents
Pine Tip Moth
Adult Pine Tip moths are small with mottled reddish patterns on forewings and tan hindwings and a 3/4 inch grey wingspan. Larvae are reddish-orange to yellow and 1/2 inch long when mature.
Host Trees
- Austrian Pine
- Mugo Pine
- Scotch Pine
- Ponderosa Pine
- Bristlecone Pine
Susceptibilities
Trees less than 10 feet tall.
Symptoms & Recognition
Moth Damage
May retard growth of the tree. Pine Tip moths feed on and destroy new growth/young shoot tissue. Injury can be difficult to recognize – tree might be stunted in growth or plants may just appear unattractive. Rarely results in death of the tree.
Management & Treatment
Parasitic wasps are a natural control for pine tip moths. Insecticides can also be used to successfully kill exposed larvae.
Andy Reago & Chrissy McClarren, CC BY 2.0, via Wikimedia Commons
Notes
Cyclical outbreaks are due to natural parasites.
Treatment Window
Tussock Moth
Douglas Fir Tussock moths produce 3/4-1 inch long larvae. These moths are grey with tufts of hair along the back. Adult moths have rusty colored forewings and gray brown hind wings. Females are thicker and wingless. The caterpillars have tufts of hair that protrude out from their body.
The Douglas Fir Tussock moth caterpillar has caused serious damage, wiping out over 25,000 acres of fir trees. These caterpillars can rapidly strip an entire forest of Douglas firs of their foliage, with activity peaking between May and June. Defoliation usually starts at the top of the affected trees, and you might spot eggs or pupae tucked into the bark. Managing an infestation typically involves applying pesticides like permethrin.
Host Trees
- Colorado Blue Spruce
- Engelmann Spruce
- Douglas Fir
- White Fir
Susceptibilities
Trees that are stressed with existing injuries.
Symptoms & Recognition
Moth Damage
Defoliation of tree will occur in a top-down pattern at the edges of the tree. They start in the newer parts of the tree and feed on old needles until the eventual death of the tree.
Management & Treatment
Chemical controls can be effective. Apply these shortly after the new growth elongates.
Jerald E. Dewey, CC BY 3.0 US, via Wikimedia Commons
Notes
Hairs of the caterpillar may cause skin irritations. Outbreaks are cyclical.
Treatment Window
Zimmerman Pine Moth
Zimmerman Pine moths are mid-sized, with grey wings adorned with red-brown and zig zags. The caterpillars are a dirty white color.
Host Trees
- Scotch Pine
- Austrian Pine
- Ponderosa Pine
- Mugo Pine
Susceptibilities
Trees planted too close together, shaded
trees.
Symptoms & Recognition
Moth Damage
Dead & dying branches will occur, often in the upper half of the tree. Pink colored pitch masses at wound sites will be oozing from the bark. Branches will be weakened and break in high winds.
Management & Treatment
Trunk sprays at central areas and up can be effective. Ensure that watering is optimal and tree is properly fertilized.
Whitney Cranshaw, Colorado State University, CC BY 3.0, via Wikimedia Commons
Notes
If the tree is showing significant signs of dieback, it’s likely too late for control measures. If the larvae have already tunneled into the tree, it’s too late for insecticides.
Treatment Window
Spruce Budworm
Spruce Budworms are 1 – 1 1/5 inches in maturity. Ivory colored spots are on each body segment with a brown head and collar. Adult moths have a wingspan of about 1 inch and are variable in color. Mottled, medium brown, dark brown or orange forewings and tan hindwings are visible.
Host Trees
- Douglas Fir
- White Fir
- Spruce
Susceptibilities
Trees near roadways.
Symptoms & Recognition
Moth Damage
Defoliation will occur as they feed on old needles. Eggs in masses are laid under needles. Discoloration of foliage will be present due to larvae feeding on buds and new shoots – trees turn red/grayish and become very thin. Multiple years of infestation can cause complete defoliation and death of the tree.
Management & Treatment
Parasitic insects, ants, spiders, birds help as natural regulating factors, as well as late spring frosts. Insecticides can also be utilized for treatment.
Notes
Budworms can create conditions that are ideal for other diseases or insects to invade.
Treatment Window
Plant Health Care Experts
The best overall care program for preventing insects from destroying your trees is a combination of pruning, watering and targeted pest control.
Our Plant Health Care team is trained to recognize signs of moth damage to help mitigate the negative effects. The death of your trees is not always inevitable, but it is a possibility we want to prevent. Contact the experts here at Front Range Arborists if you suspect an infestation.
Not Just Moth Damage
Moths aren’t the only creatures around that pose a threat to your trees. Make sure you know the signs of moth damage as well as injuries from bark beetles and borers.
Need More?
Want to learn more about insects and how they can negatively impact your trees? CSU Extension has a variety of publications across a range of topics.