Manage Box Tree Moth Infestation in Canada:
I discovered box tree moths (Cydalima perspectalis) in my yard for the first time this year.
Initially, I mistook the damage for winter kill or blight, but after a closer inspection I found a much more serious issue.
While I can manage winter kill or blight by removing the infected branches and allowing the bush to recover, the box tree moth caused such extensive damage that I lost the entire bush.
I was so disgusted by what I saw that I forgot to take pictures of the caterpillars, pupae and moths. By the end of the day, I even had a caterpillar stuck to my shirt. Gross!
I did go back the next day and all I could find was a caterpillar and a moth that took off when I arrived. He/she Moth gets to live another day. :)
Life Cycle:
Egg Stage
The female moth lays eggs on the underside of the leaves of the boxwoods. The small pale green/yellow eggs hatch into larvae.
Larval Stage:
The larvae (caterpillars photo ) with their long green bodies with 2 long black stripes along the length of their bodies, feed on boxwood foliage, causing a lot of damage. Eventually they will spin a silk cocoon to enter the pupal stage.
Pupal Stage:
When I first saw this I thought the Pupa was curled up leaf, but it was a perfect cylinder with tapered ends. After a closer look the pupa was greyish/greenish in color and hard to the touch and sure enough I could see the moth inside of the pupa. The pupa is the transitional stage between larva and adult moth.
Adult Stage:
The adult moth emerges from the pupa, mating and continuing the cycle. I was expecting to find a brown moth, but instead I found a white moth with black wing tips. Not pretty enough to allow them to eat my boxwood.
Identifying the Problem:
Look for signs such as webbing, brown leaves and frass (insect droppings).
What to do if you have a box tree infestation?
1. Manual Removal works if you have a small infestation and then just dispose of them in a sealed bag or burn them if you are allowed.
2. Pesticides: Use insecticides specifically labeled for box tree moths. Bacillus thuringiensis (Bt) is a biological control that targets caterpillars.
3. Pruning: Trim and dispose of heavily infested branches. This helps reduce the population and prevent further spread.
This what I did. So far I cut back 15 bushes. I am so glad I don't have hedges.
4. Regular Monitoring: I still have a few boxwood bushes left and I'm checking my plants frequently. Today I checked a few more bushes and they are starting to show signs.
5. Seek Professional Help for severe infestations. I would love a boxwood hedge, but with winter dieback, blight and now box tree moth I think I will stick with bushes, if I am able to save any of my boxwood.
I hope you are able to save your boxwood.
More on Box Tree Moth Infestation with pictures
Boxwood Alternatives:
Here are some options that can provide similar aesthetic qualities or functions.
1. Holly (Ilex): Holly varieties, such as the American holly (Ilex opaca) or Japanese holly (Ilex crenata), can offer year-round greenery and in some cases attractive berries. They are generally resistant to pests and diseases.
2. Yew (Taxus): Yews are evergreen shrubs that are very versatile and can be pruned into various shapes. The Japanese yew (Taxus cuspidata) and English yew (Taxus baccata) are popular choices.
3. Arborvitae (Thuja): Arborvitae varieties like the Green Giant (Thuja 'Green Giant') and the Emerald Green (Thuja occidentalis 'Smaragd') are popular for their dense foliage and ability to form privacy screens. Just needs light clipping to keep them tidy.
4. Cypress (Cupressus): Italian cypress (Cupressus sempervirens) and other cypress varieties can add a vertical element to your garden and are good for formal landscapes.
5. Dwarf Alberta Spruce : (Picea glauca 'Conica') offer dense, compact growth that can serve similar functions to boxwood.
I still love my boxwood best. :)