BIOLOGICAL CONTROL
Trichogramma wasps offer a natural, chemical-free approach to controlling moth infestations.
These tiny beneficial insects are specialist egg parasitoids that seek out moth eggs and prevent them from developing into damaging larvae.
Because moth larvae are responsible for much of the feeding damage to textiles and other natural materials, stopping the moth at the egg stage can be an important part of an effective pest management programme.
How do Trichogramma wasps work?
Trichogramma are extremely small parasitic wasps, typically difficult to see with the naked eye. Rather than attacking adult moths or larvae, they seek out moth eggs.
A female Trichogramma lays her own egg inside a moth egg. The developing Trichogramma then uses the moth egg as its host, preventing the moth larva from developing.
A new adult wasp subsequently emerges and searches for further moth eggs to parasitise. This allows the biological control agent to continue working while suitable moth eggs are present.
Which moths can they control?
Trichogramma species have been studied and used against a range of moth pests. Trichogramma evanescens, for example, is commercially used for biological control and has been investigated against clothes moths and stored-product moths.
Depending on the particular biological control product and strain, applications may include:
- Webbing clothes moth
- Case-bearing clothes moth
- Tapestry moth
- Pantry and stored-product moths
- Other susceptible moth species
The correct Trichogramma species should always be selected for the target pest.
Why use biological control?
One of the major advantages of Trichogramma treatment is that it provides a non-insecticidal method of pest control.
This can be particularly valuable in:
- Museums and historic houses
- Archives and libraries
- Textile collections
- Galleries
- Historic furniture collections
- Clothing and wardrobe storage
- Other areas containing delicate or irreplaceable materials
Because the treatment targets moth eggs rather than the materials themselves, it can be an attractive option where the use of chemical insecticides is undesirable.
Ideal for Integrated Pest Management in Museum and Heritage settings
Biological control works particularly well as part of an Integrated Pest Management (IPM) programme.
A typical approach can combine:
Monitoring → Identification → Biological Control → Inspection → Ongoing Monitoring
Pheromone traps can first be used to establish whether moths are present and identify areas of activity. Trichogramma can then be introduced to target the eggs that would otherwise develop into damaging larvae.
This approach can reduce reliance on chemical insecticides while providing an additional method of controlling established moth populations.
How is Trichogramma treatment applied?
Commercial Trichogramma products are commonly supplied in small release cards, sachets or other delivery systems containing parasitised host eggs.
The release units are positioned in areas where moth activity has been identified. Tiny adult wasps emerge gradually and search the surrounding area for moth eggs.
The exact number of release units, placement and frequency of application depends on the product, target moth species and size of the area being treated, so the manufacturer’s application instructions should always be followed.
What happens after treatment?
The wasps are extremely small and generally go unnoticed. They do not behave like the larger wasps commonly associated with gardens and picnics.
As the moth population is suppressed, fewer suitable moth eggs become available. The Trichogramma population consequently declines naturally when its host eggs are no longer available.
Importantly, Trichogramma treatment is not an instant knockdown treatment. It works by interrupting the moth’s reproductive cycle, so successful control requires continued treatment and monitoring over an appropriate period.
