Boxwood Diseases

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12

So many diseases and pests are targeting the boxwood (buxus) that entire stocks are at risk. And new boxwood diseases seem to be constantly added. After the boxwood shoot die-off - caused by the fungus Cylindrocladium buxicola - it is now the boxwood borer who is troubling the popular topiary trees and thus the gardener. But even well-known people like the boxwood flea are unfortunately not out of the world or the garden with the appearance of new boxwood diseases . With these tips you get a grip on the diseases of the boxwood.

What boxwood diseases are there?

Boxwood shoot deaths (Cylindrocladium buxicola)?

The boxwood shoot die-off is first noticeable by dark, gray-brown leaf spots that quickly grow in size and eventually flow together. On the underside of the leaf you can see countless small, white spore beds, on the shoots typical black lines. After a short time a rapid leaf fall begins and the infected shoots die. They don't sprout again later. The fungal spores attack the boxwood in wind and moisture. Leaves that have already been infested and old fallen leaves serve as the nucleus, but the wind also blows new spores into the gardens. On fall leaves, the spores can survive for years and cause new infections. Boxwood disease is particularly easy at temperatures around 25 degrees Celsius, but infection is only possibleif the leaves are continuously damp for at least 5-6 hours - without a water film, the fungal spores will not penetrate through the thick wax layer of the box trees.

The picture gallery above shows step by step which steps are necessary to curb the shoot tip death in the boxwood.

Fight boxwood shoot deaths

• In the case of mild infestation, the shoots affected by you severely cut back. The holes in the boxwood look stupid, but they grow over again and are still better than struggling with the mushroom.
• After cutting, spray with fungicides every 10 to 14 days to protect the new shoots from the fungus. However, change the active ingredients of the agents so that the fungus does not become resistant.
• Remove sick leaves: To do this, it is best to place an old bed sheet under the box plants and use a leaf rake to brush through the branches. The leaves of infected shoots fall down and can be disposed of with household waste.
• Do not cut preventively on sultry summer days, as the fungus can penetrate directly into the plant via the interfaces. If a cut cannot be avoided, then spray a fungicide.
• Only propagate your own plants, some carry the pathogen in them, but do not get sick for a long time - a danger to the garden if the newbies suddenly get sick and infect the others.
• Algae lime strengthens the boxwood against diseases and prevents fungal spores from germinating. Algae lime also dries out the spores. Algae lime is best sprayed onto the leaves by hand or with a powder sprayer several times per season.

Boxwood Borer (Cydalima perspectalis)

The caterpillars' caterpillars make their way over the boxwood from the end of March until autumn and eat the bare leaves of the shoots, whereby the leaf ribs usually remain. The caterpillars are hidden in the branches of the plants and are initially not noticed. You can recognize the boxwood borer at the latest when the shoots are bare or conspicuous webs appear. Bare eaten shoots sprout again as soon as the caterpillars are gone. Without treatment and when there are no more leaves, the caterpillars also eat the green bark of the stems. This is the end of this instinct, it dries up above the deepest feeding point, dies and does not sprout anymore. Pesticides help to fight the boxwood borer. If these do not help, you can also try these 3 home remedies:

Garden maintenance

3 home remedies for the boxwood borer

Every hobby gardener has had a box tree in his garden: they are easy to care for and can be cut wonderfully into shape …

Box Flea (Psylla buxi)

If young leaves curl up in a bowl shape (spoon leaves) so that they form a kind of ball, the boxwood flea spreads in it. Or rather, its larva. Sticky honeydew on the leaves shows that the animals are sucking on the sap. A pruning of affected shoots is usually sufficient to control the tree flea.

Box Crab (Volutella buxi)

Another mushroom that targets the boxwood. The disease causes entire shoots to die. As in the case of shoot death (cylindrocladium), in this boxwood disease spore beds form on the underside of the leaves, which are larger and orange-pink in comparison. In addition, the leaves of young shoots turn pale green and twist, later the leaves turn brown and fall off.

How to fight boxwood cancer

Cut off infected shoots and remove fallen leaves. Fertilize and water the boxwood as a preventive measure and give it a little lime to raise the pH.

Garden maintenance

Algae lime for a healthy boxwood

Box trees prefer calcareous soils: For this reason, algae lime has been sold for the boxwood for a long time and has been used successfully …

Boxwood wilt (Fusarium buxicola)

Another cause of the wilting of the boxwood is a fungus, which fortunately does not spread over a large area and is especially aimed at plants that are already weak, hungry and thirsty. First the leaves of individual shoots turn yellow, then the whole shoot dies off very quickly. The bark of the shoots becomes dark brown over a large area and softer than healthy bark.

Combat boxwood wilt

A pruning of affected shoots is usually sufficient to combat the wilting of boxwood. Preventively fertilize the plants and water them sufficiently.

As a horticultural engineer, Thomas Heß is the specialist for everything that grows and blooms in the garden: Our author explains to you when the best time for sowing, fertilizing or wintering is and how to prevent waterlogging. Benefit from his expert knowledge!