When is the best time to treat the box tree moth?

When is the best time to treat the box tree moth?

In order to successfully treat the box tree moth, it is essential to choose the right time. Find out here when to use which methods.

Even the best method to protect the widely beloved box trees (Buxus) can be useless if the timing is not right. Throughout many stages of its life, the box tree moth (Cydalima perspectalis) is practically immune to attackers. To ensure that you always have a suitable action strategy, we highlighted the right points in time for each approach in this article.

When is the best time to treat the box tree moth?

If you want to eliminate the box tree moth quickly and effectively, you have to understand its life cycle and characteristics. Based on that, you can choose the best option for your situation: using traps, pruning the box hedge, washing the caterpillars away with jet of water from a gardening hose, collecting them manually or spraying them with various products.

When to set up the box moth traps?

The short-lived adult moths of the box tree moth are mainly active at night, they mate and lay eggs. Soon after the first flight of the adult moths, the gluttonous larvae will hatch from the eggs. Therefore, observing the moth flight is the first and the most crucial step if you want to get a head start in the fight against the pest. With the help of pheromone traps you can monitor the activity of the adult moths and thus determine when the eggs and the caterpillars are to be expected. The traps should be used in June, August and September.

Note: If the season is unusually warm, the development of the moth can accelerate, so the flight of the adult box tree moths can happen sooner than expected.

When to collect the box caterpillars by hand?

The manual collection or cutting out of whole shoots with the box caterpillars is only worthwhile if the infestation is minor. The inspection of the inner and outer parts of box trees can be carried out from mid-April. Since the development time of the moth changes depending on the weather, we recommend at least monthly inspections until September.

The best scenario is to collect the caterpillars when they are still in the early larval stages and still spun into webs and leaves inside the shrub. At this point the infestation is not yet visible from the outside. In later stages, when the caterpillars live on the outer part of the box shrub, they can also be rinsed off with a jet of water from a gardening hose. You don’t have to worry about touching the box tree caterpillars. The caterpillars only pose a threat if ingested. For this reason, the disposal of the box tree moth is not as complicated as you might think.

touching box tree caterpillars
Don’t be afraid of the green larvae, they are harmless to humans (washing hands after is recommended, though) [Shutterstock.com/ Photophlox]

Tip: If you spot very young larvae and eggs of the box tree moth on the outside of your boxwoods about 2 weeks after the moth flight, immediate pruning is a good method for removing the pests.

When to use sprays against the box tree moth?

The eggs and the pupae are well protected against all sprays, the adult moths fly away and young larvae hide in their webs. If an infestation is to be treated with spraying agents, the caterpillars have to be older and live on the outer parts of the shrub so that the products can actually reach them. This is usually the case in the second half of April and early July. Of course, there are also agents that are absorbed by the caterpillars when they feed on the box tree. In order to reduce the use of harsh chemical agents, however, the use of so-called Bt preparations is recommended. Such products are highly effective against the box tree moth, but at the same time gentle to other species that live in your gardens.

Summary: when to treat the box tree moth?

  • Pheromone traps should be used in June, August and September. In unusually warm years, the moths of the box tree moth can also appear earlier.
  • It is best to check for webs, faeces and caterpillars at least once a month between April and September.
  • Two weeks after the adult moths first fly, eggs and young larvae can be removed by pruning the bush.
  • In the second half of April and at the beginning of July it is best to use sprays against the box tree moth.

In this article you can find a detailed summary of how to treat the box tree moth.

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