From the outside the boxwood may still look green, but inside webs and eaten leaves are already visible: the box tree moth often starts well hidden. DIE UMWELTBERATUNG currently points out that moths are on the move again and are laying eggs. If you check now, you can usually treat a small infestation more precisely than a shrub that has already been eaten bare.
The three-minute check on the boxwood
Put on gardening gloves and carefully spread the branches apart in several places. Pay special attention to the dense interior of the shrub, the undersides of leaves and loose webs. Typical signs are eaten leaves or leaves eaten down to the veins, droppings and spun-in plant parts.
According to DIE UMWELTBERATUNG, the caterpillars are yellowish to dark green, striped white and black, have a dark head and can reach up to five centimeters in length. Not every caterpillar in the garden is a pest: therefore, only take action when the animal and the damage correspond.
Which measure is appropriate for the finding?
| Finding | Appropriate response |
|---|---|
| No caterpillars or webbing | Continue to check regularly inside. Preventive spraying is not advisable. |
| Single caterpillars and small webs | Remove webbing and carefully pick off caterpillars. |
| Multiple infested spots | Place a light-colored cloth underneath, also rinse out the shrub from the inside with a strong jet of water and catch any falling caterpillars and eggs. |
| Severely damaged shoots | Prune back selectively. Dispose of infested prunings in a closed bag with the household waste; do not put them on the compost. |
On hot days, it's best to work in the morning or early evening. For more information on breaks, sun protection and watering times, see our guide Gardening in the heat.
Plant protection products remain the last resort
If picking off, a jet of water and targeted pruning are not sufficient, only products may be considered that are approved in Austria for the specific use. The information in the official plant protection product register and on the label is decisive. Products used in organic gardening are not automatically harmless to other caterpillars and insects either.
Preparations with Bacillus thuringiensis can be effective against feeding caterpillars. They are not used preventively. Pheromone traps mainly help to detect moth flight and thus a suitable timing for control; they do not replace the search for caterpillars in the shrub.
Check again after the first measure
Open up the shrub again after a few days at the same and at new spots. Remove any overlooked webs and check whether fresh feeding damage has appeared. Potted boxwood needs normal, site-appropriate care after a jet of water or pruning – but not automatically more fertilizer. In extreme heat, the basic rules from How to water balcony plants properly in heat.
Are other shrubs also at risk?
Boxwood is the main host plant. DIE UMWELTBERATUNG additionally names certain hollies and spindle shrubs that can also be affected. If such plants are standing directly next to it, check the interior of those shrubs as well. However, finding the box tree moth does not mean that every shrub in the garden now has to be treated.
Quick check: What you need
- Garden gloves and a light, water-permeable cloth
- a container for collecting the caterpillars and silk webs
- for heavier infestations: a garden hose and clean pruning shears
- a bag for infested cuttings
The most important step remains careful inspection: the earlier the caterpillars are discovered inside, the smaller and more targeted the intervention can be.
