As is so often the case, the pests are not a whim of nature, but were introduced by humans: “They probably came to us on a container ship because tree nurseries were keen on cheap boxwoods from Asia,” explains the Nature Conservation Association of Germany e.V., explaining the background to the spread in Europe areas. The boxwood borer is actually native to Japan and China. It was first spotted in the southern Upper Rhine in 2007, and since then the small butterfly has continued to spread and now lives in the Netherlands, Switzerland, Austria, France, Great Britain and Germany. However, it’s not the butterfly that causes so much damage to the plants – it’s the caterpillars.

In contrast to caterpillars, the boxwood moth is usually not found on boxwood trees, but on the underside of the leaves of other plants. The females prefer box trees that have not yet been infected to lay their eggs, so that new generations of box tree moths (up to four) emerge from March until late summer. The caterpillars hatch after just three days: They can be up to five centimeters long, are yellow-green to dark green and black in color, have black dots and white bristles. Because of their preference for older leaves, they start their feeding attacks inside the plant – and work their way outwards. As a result, the beginning of the boxwood’s decay usually remains undetected. A watchful eye is therefore¬†important to detect the infestation.

To find out whether boxwood borer caterpillars are attacking your plants, you should pay attention to the following signs that indicate an infestation:

Two to four generations of boxwood borer caterpillars can attack your garden each year, so you should remain on alert from spring to late summer – even if you think you have already removed all the pests from your boxwoods. The following tips are among the most effective methods to combat caterpillars:

Last but not least, you can of course also take preventative measures to ensure that the box tree borer – or more precisely its caterpillars – do not infest your plants. These include the following:

Sources: Nabu

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