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Pheromone traps are one of the most talked-about tools in the fight against box tree caterpillar, but there is a lot of confusion about what they actually do. Can a simple trap really protect your box hedge? The short answer is: not on its own — but as part of a broader strategy, a pheromone trap is genuinely valuable and well worth the modest investment.
In this review, we explain exactly how pheromone traps work, what they can and cannot do, how to get the best results from them, and which products we recommend for UK gardeners.
| The Bottom Line Pheromone traps are an excellent monitoring tool that tells you exactly when box tree moths are active in your garden, allowing you to time your spray treatments perfectly. They are NOT a standalone treatment and will not eliminate an infestation on their own. Use them alongside Xentari for the best results. |
How Do Pheromone Traps Work?
Box tree moth pheromone traps use a synthetic version of the chemical signal (pheromone) released by female box tree moths to attract males for mating. The synthetic pheromone is impregnated into a small rubber or plastic lure capsule, which is placed inside a sticky trap or funnel trap.
Male moths detect the pheromone from a distance and fly towards the trap, believing they are approaching a receptive female. Once inside the trap, they become stuck on the adhesive surface (in sticky traps) or fall into a collection chamber (in funnel traps) and cannot escape.
Because only male moths are attracted by the female pheromone, the trap catches males exclusively. Females continue to fly, mate with any males that avoid the trap, and lay eggs as normal.
Pros and Cons at a Glance
| Pros | Cons |
| ✓ Completely non-toxic and pesticide-free | ✗ Only catches male moths — females still lay eggs |
| ✓ Easy to set up — takes 5 minutes | ✗ Will not eliminate an existing infestation on its own |
| ✓ Low cost (typically £8-15 per trap) | ✗ Limited range — each trap covers roughly 10-15 metres |
| ✓ Tells you exactly when moths are active | ✗ Must be combined with other treatments for effective control |
| ✓ Helps you time spray treatments perfectly | ✗ Lures need replacing every 4-6 weeks |
| ✓ Works all season from April to October | ✗ May attract moths from neighbouring gardens (debated) |
| ✓ No maintenance beyond lure replacement |
What Pheromone Traps Are Good For
1. Early Warning System
This is the single most valuable function of a pheromone trap. When the first moths of the season appear in your trap, you know that egg-laying has begun or is imminent. This is your signal to start inspecting your box plants closely for eggs and small caterpillars, and to prepare your Xentari spray. Without a trap, you might not notice moth activity until the caterpillars are already large and causing visible damage — by which point significant harm has been done.
2. Treatment Timing
Knowing exactly when moths are active allows you to time your spray applications with precision. Apply Xentari 10-14 days after the first moths appear in your trap — this targets the newly hatched caterpillars at their smallest and most vulnerable, before they can cause significant damage. This proactive approach is far more effective than the reactive approach of waiting until you see damage.
3. Seasonal Monitoring
By checking your trap weekly throughout the season, you can track the distinct flight periods of each moth generation. In the UK, you will typically see two clear peaks of moth activity — one in May-June (first generation) and another in August-September (second generation). In warm years, a third smaller peak may appear in October. Each peak corresponds to a new wave of egg-laying and a new crop of caterpillars that will need treatment.
4. Population Reduction (Limited)
In a small, enclosed garden where your box plants are relatively isolated, trapping a significant proportion of the local male moths can reduce the mating success of the population and therefore reduce the number of fertile eggs laid. However, this effect is limited. In larger gardens, open settings, or areas where neighbours also have box, enough males will avoid the trap to maintain normal reproduction. Think of population reduction as a bonus rather than the primary purpose.
How to Set Up and Use a Pheromone Trap
- Purchase a box tree moth pheromone trap kit. Most kits include the trap housing (triangular/delta or funnel-shaped), a sticky insert or collection chamber, and one or two pheromone lure capsules.
- Assemble the trap according to the instructions. Place the pheromone lure in the holder inside the trap.
- Hang the trap at approximately head height (1.5-1.8 metres) near your box plants. Ideal placement is 2-3 metres from the nearest box plant, in a relatively sheltered spot that is not exposed to strong winds. Do not hang it directly in the box hedge — a nearby fence post, tree branch, or shepherd’s hook works well.
- Deploy from mid-April to catch the first emergence of overwintered moths. Keep the trap active through to the end of October.
- Check the trap weekly. Count the number of moths caught and note the date. This data helps you track flight periods and time treatments.
- Replace the pheromone lure every 4-6 weeks. The synthetic pheromone gradually evaporates and loses potency. Most manufacturers sell replacement lures separately.
- Replace sticky inserts when they become full or lose their adhesive quality. In peak season, this may be needed every 2-3 weeks.
- At the end of the season (late October/November), remove and dispose of the trap. Store reusable trap housings for next year. Purchase fresh lures the following spring.
| Placement Tip If you have box plants in multiple areas of your garden, consider using two traps placed at opposite ends. This gives better coverage and helps you identify which areas have the highest moth activity. |
| Box Tree Moth Pheromone Trap Kit Complete kit with trap housing, sticky insert, and pheromone lure. Deploy from April to October for season-long monitoring. [AFFILIATE LINK: Insert your Amazon Associates link for pheromone trap kit here] |
| Replacement Pheromone Lures (Pack of 2) Replace lures every 4-6 weeks to maintain trap effectiveness throughout the season. Buy on Amazon |
What to Do When You Catch Moths
When you start catching box tree moths in your trap, follow this action plan:
- Week 1 after first catch: Begin inspecting your box plants closely every 3-4 days. Part the foliage and look inside for eggs (tiny flat yellow-green clusters on leaf undersides) and very small caterpillars (1-3 mm, pale green).
- 10-14 days after first catch: Apply your first Xentari spray, even if you have not yet spotted caterpillars. The eggs will be hatching around now and the tiny caterpillars are at their most vulnerable. This preventative timing is far more effective than waiting for visible damage.
- 7-10 days after first spray: Apply a second Xentari spray to catch any caterpillars that hatched after the first application.
- Continue monitoring: Keep checking the trap weekly. When you see a second peak of moth catches (typically August), repeat the treatment cycle for the second generation.
Do Pheromone Traps Attract More Moths to Your Garden?
This is a common concern, and understandably so. The answer is nuanced. Pheromone traps do attract male moths from the surrounding area — that is how they work. However, the range of attraction is limited to approximately 10-20 metres, and the moths drawn in are males that were already flying in the vicinity searching for females. The trap is not pulling moths from miles away.
More importantly, even if a trap does draw in a few additional males, those males are being caught and killed rather than mating. The net effect is neutral to positive. The monitoring benefit far outweighs any theoretical risk of attracting extra moths.
Which Trap Design is Best?
There are two main pheromone trap designs available for box tree moth:
- Delta (triangular) traps: Flat, tent-shaped traps with a sticky insert on the base. Moths fly in through the open sides and stick to the adhesive. These are the most common consumer design, affordable, and widely available. The main downside is that the sticky insert can become saturated in areas with high moth populations and needs frequent replacement.
- Funnel traps: Larger, bucket-shaped traps where moths enter through a funnel at the top and fall into a collection chamber below. These do not use sticky inserts and can hold many more moths, making them better for high-population areas. They are slightly more expensive and bulkier but require less maintenance.
For most domestic gardens, a delta trap is perfectly adequate and the most cost-effective choice. If you have extensive box hedging or live in a heavily affected area (London, south-east England), consider upgrading to a funnel trap.
Frequently Asked Questions
Do pheromone traps kill box tree caterpillars?
No. Pheromone traps catch adult male moths, not caterpillars. The caterpillars are the larval stage that causes the damage to your box plants. To kill caterpillars, you need a treatment such as Xentari (Bacillus thuringiensis). Pheromone traps are a monitoring tool that helps you detect when moths are active and time your caterpillar treatments effectively.
How many pheromone traps do I need?
For a small to medium garden with box in one area, a single trap is sufficient. For larger gardens with box plants in multiple locations, use two or three traps spaced at least 10 metres apart. Each trap has an effective attraction range of approximately 10-20 metres.
When should I put out my pheromone trap?
Deploy from mid-April. The first overwintered box tree moths typically emerge from late April to early May, depending on spring temperatures. Having your trap in place from mid-April ensures you catch the very first moths. Keep the trap active until the end of October.
How often should I replace the pheromone lure?
Every 4-6 weeks. The synthetic pheromone gradually evaporates and the lure becomes less attractive to moths. During the peak season (May-September), replacing every 4 weeks gives the best results. Most manufacturers sell replacement lures in packs of 2-3.
Can I use a pheromone trap instead of spraying?
No. Pheromone traps alone will not protect your box plants from caterpillar damage. They catch male moths but females continue to lay eggs. The trap is a monitoring and early warning tool that should be used alongside a treatment programme (ideally Xentari). Think of the trap as your alarm system and Xentari as your firefighter.
My trap is catching lots of moths — is that bad?
It means box tree moths are active in your area, which is valuable information. Every moth caught in your trap is one fewer moth available to mate. More importantly, it tells you to start inspecting your box plants immediately and prepare to spray. A busy trap is doing its job — better to know about the problem than to be caught unaware.