the essentials in brief
- Box tree moths are difficult to spot early
- Webbing and eaten foliage are indications of an infestation
- Infested parts of the plant should be disposed of as quickly as possible - and in no case on the compost
- Box tree moths can be collected or controlled directly using ecological means
The problem of the box tree moth infestation
A boxwood moth infestation is not only annoying, it is quite critical. Because apart from the fact that carefully tended box hedges or spherical box trees are ugly eaten away and spun over with webs, it is also not easy to control the box tree moth. On the one hand, an infestation is usually only recognized when the crown has already been ugly eaten away, on the other hand, several generations can develop within one season.
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Another problem is that when you buy new plants you can get hold of the pesky pest again. The box tree moth became so widespread especially through the plant trade.
Is the box tree moth poisonous?
In the case of exotic plants and insects, one quickly wonders whether they might not be poisonous to humans, birds or other animals. This is only indirectly the case with the box tree moth. Although it is initially not poisonous, it becomes so in the course of the boxwood occupation. The plant contains some poisons, especially alkaloids, which the larvae store in their bodies when they eat. As a result, the above-mentioned predators also absorb these poisons when they feast on the caterpillars. However, this does not seem to pose a serious threat to the songbirds.
What can be done against the box tree moth?
If an infestation is already underway, it is important to take countermeasures as early as possible. If you are thorough with the first generation, you may have peace of mind for the rest of the season.
Basically, for the sake of nature and your own health, you should always first try to combat the box tree moth biologically.
Especially when the infestation has not progressed very far, it is advisable to counter the pest in a mechanical way first. The motto “fight naturally” is thus best fulfilled.
Mechanical methods are:
- Blow off
If the number of larvae is manageable, you can use tweezers to collect the animals, which of course requires some skill.
The somewhat coarser variant is the garden hose or low pressure cleaner or a leaf blower. You can use it to flush or blow the caterpillars out of the bush and catch them on a film that has been spread out under the plant beforehand.Youtube
Ecological means: Box tree moth control without chemicals
Effective chemical-free agents are:
- Bacillus thuringiensis products
- Oil products
- Lime and rock flour
Bacillus thuringiensis - Xentari
The bacterium Bacillus thuringiensis is an effective means of biological control of the boxwood moth - it colonizes the caterpillars parasitically and causes them to die. Products with the bacillus are sold under the name Xentari, for example by the Neudorff company “Raupenfrei”.
Products based on neem oil are currently booming as gentle pesticides. They are also an effective aid against pests of the box tree. The active ingredient azadriachtin from the neem tree seeds is stored in the leaves of the boxwood and inhibits the moulting and thus the development of the caterpillars. It is particularly advantageous that you stop eating away at the leaves immediately. Note that the neem oil treatment should not be done in high heat if possible. In hot weather, it is therefore best to spray after sunset.
In order to distribute the active ingredient as thoroughly as possible on the box, it is advisable to use a concentrate. This is diluted with water (the ratio is specified on the product container) and placed in a disperser. To reduce the surface tension of the mixture, you can add a drop of detergent or some soft soap (€ 17.27 on Amazon *). This will give you more thorough coverage and better success rates.
Ballistol oil can also be used as an antidote to a boxwood moth plague. The advantage here is that the agent is ready-made in spray cans. That makes the application easier. The oil works mainly by obstructing the gas exchange in the eggs and clogging the larvae 's airways.
Vinegar is also one of the tried and tested home remedies against the box tree moth. It makes the pages of the book inedible for the pests. It is best to combine the vinegar with other household remedies, i.e. with oil and a little water. This adds to the airway clogging effect and increases the overall effect.
In addition to cake batter, baking powder has always found many other uses. In addition to stains, it should also help against the box tree moth. To do this, a solution is mixed with water and sprayed onto the box using a disperser.
Algae lime in powder form is normally used successfully against fungal diseases in box trees. But lime can also work against the box tree moth. The leaves covered with the lime powder are unattractive for the larvae to eat. You can also try finely crushed shell limestone.
Primary rock powder
A similar effect can be achieved with primary rock powder. If the rock flour (14.95 € at Amazon *) is deposited on the leaves of the box tree, it is more difficult for the borer to lay eggs.
When to inject
A spray regimen with organic control fluids should be used as soon as you discover a population of boxwood moths. It is always better if you completely exterminate the first generation of moths in the season and thus prevent a subsequent generation. To effectively eradicate a pest population, you should give three thorough sprayings over a period of approximately 3 weeks.
Chemical agents are of course not advisable because of their generally harmful effects on the biosystem of the garden and the environment. However, if none of the ecological means works and you don't see any other way out, you can also fall back on them.
Bayer's “Pest-Free Calypso” product, for example, is effective. Apart from its not exactly environmentally friendly character, the application can also harm you. In particular, allergic reactions can occur in contact with the skin; the agent should never get in the eyes or be swallowed.
Under the trade name “Lizetan” the Protect Garden company sells a spray based on the synthetically produced neem oil tree active ingredient azadriachtin. For the box tree moth, for example, the product “Lizetan Pest Free” has proven to be very effective. In principle, it has the same systemic effect as organic neem products, but is less gentle and can cause allergic reactions.
Bi 58 is not approved for outdoor use, only use on ornamental plants in greenhouses is permitted. Bi 58 is a ready-to-use spray that works with the active ingredients abamectin and pyrethrins. Abamectin has a damaging effect on the nervous system of pests, pyrethrins acts as a contact poison. The sprayed insects die quickly, but the agent has a long-term damaging, toxic effect on aquatic organisms.
The insecticide “Pest Free Careo” from Celaflor is also a chemical spray that can be used against the boxwood moth. Its active ingredient is the food poison acetamiprid, which paralyzes and causes the pests to die. However, the concentrate is also toxic to aquatic organisms.
Traps can also be used against boxwood moth populations. Above all, pheromone traps are used against the pest.
A pheromone trap makes use of the attraction of scents during the mating process of pest insects. Synthetically produced attractants of female insects, technically pheromones, are either combined with glue on tablets or injected into a trap container. With the first method, the male insects that are attracted simply stick to it, with the second they get into the trap container, which they can no longer leave. By catching the male boxwood butterflies, the mating rate and thus reproduction is reduced.
The container traps usually consist of a trap body and two depot chambers for the attractant, a pheromone gel, which is filled with a syringe. This gel is usually also available as a refill pack. Traps from Natria (Bayer), von Solabiol or von Neudorff, for example, work with this principle. The Neudorff trap is available under the brand name Neudomon as a specific box tree moth variant.
Experience: moderate effectiveness
The trap method is quite uncomplicated because only the trap has to be hung up and the attractant depots have to be refilled every few weeks over the season. However, the effect is by no means as effective as with targeted treatments on the Buchs using home remedies and spray cures. In the end, the number of males is only slightly reduced, but by no means set to zero. As a rule, there are still individuals left who can mate with females.
Pheromone traps are therefore actually more used in agriculture and forestry for monitoring, i.e. for diagnosing the extent of the population, and less for the actual limitation of damage. In this respect, however, you can also use such traps for inspection, i.e. to determine whether box tree moths are in your garden at all. In this way you can prepare for a targeted fight.
So that you don't even get into trouble with the box tree moth, it is worth taking precautions. It starts with the plant procurement. Before buying a box tree, inspect it with an eagle eye: if you can see fine webs or small crumbs of feces, a box tree moth infestation is fairly certain.
Spanning box trees with a fine net can also be helpful as it prevents the moths from laying eggs.
Dispose of infested box trees
Finally, a word about the correct disposal of infected box tree branches or whole plants. Since the pest has spread so massively in recent years, every hobby gardener has a certain responsibility to prevent further spread. Although there is no official reporting requirement for a boxwood moth infestation, in the interest of the general gardening community, the control should be as thorough as possible.
- No disposal on the compost
- Ideal: burn
Infested plant material does not belong in the compost!
So if you are dealing with a strong, stubborn population and your boxwoods are badly eaten away, it is necessary to thoroughly remove infested plant material not only for aesthetic reasons, but also to prevent it from spreading. Puped moths can still sit on the eaten and dead shoots of a Buxus, which come together in a radical cut. So that they cannot cause any further damage, the clippings must never be disposed of on the compost. There the caterpillars can develop further and the trouble starts all over again.
Burning is best
It is best to have cut, infested boxwood branches burned in a recycling facility. This is the safest way to kill the pest. You should at least dispose of the clippings in the household waste, where the larvae that are still present have less chance of developing into moths.
Particularly endangered areas
In Germany, those in the Rhineland, the Rhine-Main area and the southwest are particularly badly affected by the box tree moth plague. The pest feels particularly at home here because of the warm climate. That is why the German Horticultural Association explicitly warns against planting box trees in these regions.
Facts about the box tree mothZoology, Origin and Distribution
The box tree moth is zoologically called Glyphodes perspectalis and is a small butterfly. It belongs to the family of the proboscis, which are mainly found in tropical regions. The box tree moth is also not native to us. It originally comes from East Asia, from where it was introduced to us in Central Europe around 2007 - probably through the plant trade. Since then, to the chagrin of many hobby gardeners, its spread has spread rapidly. Unfortunately, it is not easy to fight either. But you don't have to give up.
In order to be able to recognize the box tree moth, you also need an attentive eye because the caterpillars are difficult to make out in the green box leaves. However, the earlier an infestation is detected, the higher the chances of successful control.
Appearance of the moth
An adult boxwood moth has a wide, spread triangular shape about 40 mm wide and 25 mm long. Its wings are rimmed creamy white and brown. In the middle of the upper brown border, if you look closely, you can see a small, crescent-shaped spot on both sides. But there are also very brown specimens.
Appearance of the caterpillars
The boxwood moth caterpillar is about 5 cm long and yellowish green in color. A black-brown-white, dotted striped pattern runs on the back. The head is black and the caterpillar is covered with white bristles all over the body.
Actual damage from larvae
The real culprits that cause the box trees to be destroyed are not the adult moths, but the larvae. Once a box tree moth has grown into a finished butterfly, it has almost only the task of caring for offspring and does not live long after that. The pest spends most of its existence eating to prepare for its egg-laying destination. As a moth, by the way, it hangs less on box trees and more on other plants.
The box tree moth, on the other hand, always lays its eggs on box trees. This is where the larvae hatch and wrap themselves in white webs over the winter. The caterpillars only become active when the frost has clearly passed. Then they leave their web cave and begin to feast on the leaves of their host plant. This gives them the energy to grow and to complete several stages of development.
Finally, like all butterflies, they retreat into a pupa in order to transform themselves into a butterfly.
Since the hatched boxwood moth caterpillars overwinter in relatively clearly visible webs in the boxwood, you can already see an infestation in the cold season.
When the caterpillars start their voracious forcing in March, the plant is gradually defoliated and, without countermeasures, soon gives a sad, bare picture. So keep an eye on your box by March at the latest - because the caterpillars start to eat from the inside of the crown, so that the little tree looks flawless on the outside for longer.
When there are no more juicy leaves left, the caterpillars will also attack the bark of the younger shoots and cause them to die off. A clear indication of a box tree moth plague is incidentally the remaining leaf skeletons, because these are spurned by the parasites.
The boxwood moth has only recently immigrated to us and its natural predators from China and Co. have not accompanied it. Nevertheless, some native species that are willing to adapt seem to have adjusted to the new food supply and to have put the boxwood moth larvae on their menu. These include mainly sparrows, chaffinches, great tits and some species of wasps.
Can a boxwood be resistant to the boxwood moth?
In the course of the massive spread of the box tree moth, the demand for Buxus varieties that are resistant to the pests is increasing. After all, the box tree is a firmly established cultural asset in local gardening history and has a great passion.
Unfortunately, there are no resistant Buxus varieties so far. So if you absolutely do not want to do without the classic hedge and ball-cut plants, you have to live with the risk of the borer infestation and, if the worst comes to the worst, accept the effort involved in controlling it.
Small bright spot
However, it is a bit comforting that there are at least variants that seem to be a little less susceptible. These include above all the varieties of the small-leaved boxwood, botanically Buxus microphylla. Attractive varieties include the 'Herrenhausen' or the 'Faulkner'.
If you want to be on the safe side and are not too attached to the real Buxus, it is also worth considering switching to similar small trees. So you can avoid the annoying moth in the long term and still enjoy pruning-compatible, accurately malleable and robust shrubs.
Suggestions would be:
- Dwarf privet
- Dwarf yew
- Small-leaved rhododendron
Especially the varieties of the dwarf privet are an alternative to the boxwood. With its small, elliptical leaves, it is very similar to the box tree and also has a very comparable, low-density habit. Compared to other privet species, it remains rather small at 70 to 100 cm in height and also grows quite slowly. It is also undemanding, hardy and evergreen.
The dwarf yew, for example, has a somewhat more needle-like, but just as dark green and dense appearance. Like box trees, it can be cultivated in a bucket into clearly shaped silhouettes and is just as evergreen. The small wood is also suitable as a bed border. The red berry fruit decoration is a nice addition!
The small-leaved rhododendron has somewhat larger, but small leaves for its genus. Like the dwarf yew, it grows compact and spherical and is therefore a good substitute for boxwood. It is also very robust and evergreen and boasts decorative flowers.