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When it comes to garden pests, few are as destructive as the box caterpillar.

Just before we get started though, double check if you’ve got box blight or box caterpillar as the two are often confused with one another. I’ve written an article comparing box blight vs box caterpillar.

These voracious creatures can wreak havoc on your beloved box hedges and knot gardens, defoliating them and leaving them weak and vulnerable.

If you’ve discovered an unwanted box caterpillar infestation, you may be wondering if there’s a cost-effective, natural solution to these persistent pests.

Surprisingly, your kitchen may hold the key and that comes in the form of dishwashing liquid!

In this article, we’ll explore the idea of ​​using washing up liquid to repel the caterpillars and whether or not it’s a viable option.

box caterpillar washing up liquid

box caterpillar on box hedge

Understanding The Box Caterpillar Threat

Before we dive into the potential benefits of dishwashing liquid, it’s essential to understand the enemy we’re dealing with.

Box caterpillar, scientifically known as Cydalima perspectalis, is native to Asia and was accidentally introduced to Europe in the early 2000s.

Since then, they have become a major threat to box hedges across most of Europe and other parts of the world.

These caterpillars have a distinctive look with their black and white stripes, and they can quickly wreak havoc on box hedges.

If left unchecked, they can cause severe damage to an entire box hedges and topiaries, which can take years to recover (if they don’t die).

The Theory Behind Washing Up Liquid

The idea of ​​using dishwashing liquid as a natural insecticide against the caterpillar is based on its ability to disrupt the outer protective layer of this pest.

Like many insects, the caterpillar has a waxy coating on their bodies that helps them to retain moisture and protect them from dehydration.

Washing up liquid contains surfactants that break down this protective coating, causing the caterpillars to dehydrate and eventually die.

How to Use Washing Up Liquid to Control Box Caterpillar

If you decide to try dish soap, follow these steps to use it safely and effectively:

Identify infected areas:
Carefully examine your box hedges to identify areas affected by caterpillar larvae.

Look for telltale signs like fallen leaves, webbing, skeletal leaves or the caterpillar itself.

Mix solution:
Dilute mild, biodegradable dish soap with water.

The recommended ratio is one part washing up liquid to ten parts water.

Avoid using concentrated or antibacterial formulations, as they can harm your plants.

Spray affected areas:
Use a spray bottle or horticultural sprayer to spray the soapy solution directly onto the affected caterpillars, webs, and foliage.

Be sure to thoroughly cover all infested areas.

spraying a box hedge with washing up liquid
Watch and repeat:
Check your plants regularly to assess the effectiveness of the treatment.

If necessary, repeat the procedure every 5-7 days until the caterpillar population is under control.

Pros and cons of using dish soap

Using washing up liquid as a natural remedy to treat box caterpillar has both advantages and disadvantages:


  • Cost Saving: Washing up liquid is an inexpensive alternative to commercial pesticides and can be found in most households.
  • Non-toxic: Unlike chemical pesticides, washing up liquid poses minimal risk to humans, pets, and beneficial insects when used as directed.
  • Easy Access: You don’t have to go to a specialty store to buy it, this makes it a convenient  and easy accessible solution.


  • Limited Research: While there are anecdotal reports of washing up liquid’s effectiveness against caterpillars, scientific studies specifically focused on box caterpillars are scarce.
  • Potential plant damage: Overuse or using highly concentrated solutions may harm the foliage of your boxwood plants. Always test the solution on a small area first and closely monitor the plants.

Hopefully this article has helped you determine if you’re going to attack your pesky box caterpillar washing up liquid.

If you have any other questions or would like any more articles don’t hesitate to contact us.