1. Is it worth trying to control the Box Tree Moth ?

Once the Box Tree moth has newly established itself in an area, it is likely that untreated Box Tree plants will repeatedly fall victim to their voracious larvae (caterpillars). In moderate climates such as in the UK or central Europe, up to three generations of Box Tree Moths are possible every year, each of which involving a fresh batch of caterpillars. A single female moth can lay well over 100 eggs, resulting in sufficient caterpillars to defoliate a single Box Tree if left untreated.

As a result, one has to decide whether to (1) remove all Box Trees and replace with different plants, or (2) to regularly use control measures, either prophylactically, or after discovery of plant damage / feeding larvae (note: damage can be extensive before it becomes apparent to the untrained eye) or the presence of the moth (e.g. on the basis of male moths caught in a Box Tree Moth pheromone trap). If one opts for the control route, one should be aware of the time and costs involved, in addition many of the effective measures are poisonous for other insects or plants and thus not particularly environmentally friendly.

In most cases, especially in areas where Box Trees are commonly found (thus providing many host plants for moth propagation), it is likely that alternative plants are the more sensible option.

2. Chemical Pesticides

Several chemical pesticides are available for the treatment of Box Trees infested with Box Tree Moth larvae. The trade names will differ depending on country, but pesticides with the active ingredients Acetamiprid or Thiacloprid are effective. Plants are usually sprayed with a dilute aqueous solution of the pesticide and the agent spreads systemically to any untreated parts of the plants. Treated plant material is toxic when ingested by the caterpillars. The length of protection varies and repeat spraying for successive generations may be necessary in a single year.

3. "Biological" Treatments

The caterpillars of the Box Tree Moth be killed by application of Bacillus thuringiensis spores to infested Box Trees. These are applied in the same way as chemical pesticides. After ingestion, the spores soon germinate and the Bacillus thuringiensis bacteria lead to rapid appetite loss and ultimately death of the caterpillars.. Over time the spores are washed of the plants by rain, but the may remain active in the ground for several years and can be hazardous for some other insects.

Pheromone traps can be used to attract and kill male moths. However, although they reduce the male population, they are not an effective control measure in themselves. Their purpose is to identify the presence of moths in the area so that effective measures can be timed accordingly.

4. Alternative Control Measures

Smaller Box Trees exposed to sunlight may be covered with dark plastic sheeting for several hours, since the caterpillars can be killed by high temperatures..  Excessive temperatures may however damage the trees so care must be taken. Trees may be covered with nets to prevent the females laying eggs, however given that trees would need to be covered for about one month, three times a years, the method does not really rmake sense for trees that are only of decorative value only. Infestations can be reduced by spraying the trees down with a high pressure hose, yet of this method will only reduce larval numbers, rather than achieve complete removal. Trees may also be cut back to remove areas of major damage. Disposal of affected Box Trees and parts thereof may be subject to local pest control regulations, and should be performed accordingly.