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The voracious larvae of a box tree moth can “defoliate” and kill any box tree in record time. The earlier the pests are discovered, the greater the chance of saving the box after all. This is how you recognize the annoying box tree moths.
In a nutshell
- feared pest on box trees
- distinguish between moths and larvae
- Eggs only a few millimeters in size
- Infestation is usually discovered too late
butterfly
The box tree moth, scientifically Cydalima perspectalis, can be described as a newcomer to the garden. The small butterfly only immigrated from Asia at the beginning of this millennium. His presence will not be of a temporary nature, as he finds ideal living conditions in this country. The butterfly itself does not damage the boxwood directly, but its larvae. Nevertheless, the alarm bells should ring for every boxwood owner when small butterflies fly around the evergreen shrub in spring or summer. Because wherever the box tree moth can be seen, it will soon be laying eggs. How to recognize the box tree moth:
- Wingspan is 4 to 4.5 cm
- spread wings point obliquely downwards, are rounded
- Wing color is silky white
- Fore and hind wings are thickly bordered brown-black
- rarely white-beige, brown or almost black specimens
- Abdomen is color matched to the wings
- black compound eyes
- long, thin antennae
Tip: You can get a special pheromone trap commercially that you can use to attract male box tree moths. This is not an effective control method, but a reliable way of detecting the box tree moth and taking timely action.
eggs
In our latitudes, the box tree moth usually produces two new generations per year. The first eggs are laid around April, followed by another in July. In southern Germany, where the climate is generally warmer, a third or even fourth oviposition can also take place.
- each butterfly lays up to 150 pieces
- they are lenticular, pale yellow and only a few millimeters in size
- The place of storage is usually a box tree that has not yet been infested
- 20 eggs each lie close together on the underside of the outer leaves
- shortly before hatching, small black dots become visible
caterpillars
After hatching, the larvae are small and yellowish. But their change is quick. You can recognize adult box tree moth caterpillars by the following characteristics:
- Length of up to 5 cm
- yellow-green to dark green ground colour
- black and white vertical stripes
- black dots are arranged along it
- brown-black head capsule
- white bristles
Keep an eye out
The caterpillars of the box tree moth are large and conspicuous and yet the infestation is usually discovered too late. This is because the hatched larvae migrate into the opaque interior of the boxwood and from there they can eat their way out unnoticed. When they reach the outside of the crown, the infestation is considered advanced. But even then, they don't immediately attract attention, because they hardly stand out from the background because of their pattern. It is therefore important to take a close look at the slightest suspicion or even as a preventive measure. A look inside the crown of leaves should not be missing. These signs indicate a caterpillar infestation:
- Leaves and shoots are eaten
- white webs are visible in the foliage
- tiny crumbs of feces on foliage
- leaf spots (yellow or brown)
- bare (bare-eaten) branches
combat
Discovered eggs are removed from the tree with a courageous pruning and disposed of in a sealed bag as residual waste. Small amounts of pupated larvae can be collected by hand, large amounts must be awaited control until hatching. The caterpillars must be removed from the boxwood or killed as quickly as possible. Which measure can help most effectively must be decided on a case-by-case basis. The following is possible:
- collect by hand
- Rinse off the branches with a high-pressure cleaner
- blow away with a leaf blower
- Spray several times with a preparation made from neem oil
- use the bacterium Bacillus thuringiensis
- sprinkle with algae lime
- use chemical spray (only as a last resort)
- settle natural enemies
A box tree that obviously cannot be saved should be cleared and disposed of as soon as possible. So that the box tree moth cannot spread further.
Tip: If you blow or flush out caterpillars from the boxwood, you should definitely spread out a large tarpaulin beforehand and fasten it with stones. This will make it easier for you to collect and dispose of all specimens once the procedure is complete.
frequently asked Questions
Can you prevent the box tree moth from laying eggs?In the spring you can cover your buchs with a very close-meshed net. The butterflies then have a hard time laying their eggs in the foliage.
How quickly do larvae hatch from the eggs?The first larvae hatch just three days after the eggs are laid. Anyone who discovers eggs on their boxwood should therefore plan and tackle the fight immediately.
When in the year can I expect the first caterpillar?Caterpillars of the box borer go through several stages of development. This also means that they overwinter in the boxwood. These specimens can be seen feeding as early as March of the following year. The danger of caterpillars has not been averted until well into September, since this year's generations are added to the overwintering larvae.
Do box tree moth roughnecks have natural enemies?It is worth using nesting boxes to attract chaffinches, great tits, redstarts and sparrows to the garden, as they eat the larvae of the box tree moth. Another predator is the Gallic paper wasp.