Until about ten years ago, the boxwood was considered an uncomplicated and easy-care tree, which is extremely versatile in the garden and can easily reach an age of several hundred years. In 2007, however, a moth appeared for the first time, the caterpillars of which are seriously endangering today's boxwood population. In addition to the shoot death caused by the bacterium Cylindrocladium buxicola, the so-called box tree moth is one of the most dangerous garden pests today.

More and more pests and diseases are being introduced from other countries

Boxwood diseases on the rise

A few years ago, little was known about the way of life, reproduction and ways of controlling the box tree moth. At first, the local wildlife didn't seem to be able to do much with the green caterpillars either, it was even assumed that the pests were poisonous for hungry birds. But from year to year the scientific knowledge has increased, from 2015 to the present day numerous new ways to combat the invasive insect have emerged.

It has also been known since around 2016/2022 that songbirds have also adapted to the borer caterpillars as a new source of food: Tits and sparrows in particular are reported to be devouring countless of the pests. Also new from 2022 is the information that slugs are apparently also hard-working caterpillar eaters: Some gardeners reported a noticeably high number of slugs in some boxwood bushes, in which there were no or only very few borer caterpillars to be found.

What helps against the box tree moth?

One thing above all helps against the box tree moth: extremely quick action. Several hundred to a thousand caterpillars can sit in larger bushes, which can practically eat the infested specimens bare overnight. Therefore check the box for an infestation as daily as possible and hang up pheromone traps in order to be able to use them to estimate the presence of adult moths and thus the right time to combat them. In this case, a close-meshed net placed over the box can prevent egg laying and thus prevent infestation. After an infestation, the only thing that helps is severe pruning and a plastic bag that is placed over the affected plant for a few hours and kills the caterpillars by heating. Certain biological insecticides, such as those using the bacterium Bacillus thuringiensis, are also effective.

What helps against boxwood dieback?

Another boxwood disease that has only been known for a few years is shoot death caused by the fungus Cylindrocladium buxicola. In many cases there is no rescue in the event of an infestation, so that only disposal remains. However, there are some preventive measures you can take:

  • sunny, airy location
  • balanced supply of nutrients and water
  • never water over the leaves
  • keep them as dry as possible
  • no pruning on warm, humid days
  • preventive treatment with appropriate fungicides
  • Plant insensitive varieties such as 'Herrenhausen', 'Faulkner' or 'Arborescens'

tips

Be careful with the hasty disposal of box trees that are supposedly infected with Cylindrocladium buxicola: This fungus is not always behind a shoot dieback, sometimes it is another - easily treatable - fungal disease or a pest infestation, for example with spider mites.

Category:

Vegetable garden