What can you do against diseases of the Box ?

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This evergreen shrub can have a few worries, especially with the appearance of new diseases. However, good cares should keep it looking great! Spot the symptoms and act at the right time and the right way.

Falling leaves
It is the most common, widespread disease for Buxus. A lot of ambient humidity, especially if the site is not well-ventilated (a garden surrounded by high hedges or by walls) encourages pathogenic fungus of the Buxus, responsible for the falling of the leaves. This disease is contagious and you must act quickly. Act if possible in a preventative way, as once they are thinned out, the bare stems will have difficulty in becoming green again. The remedy ? Spraying soluble sulphur (the same one than the one used on fruit trees) is enough to protect Buxus against pathogenic fungus. Spray in dry weather and with a temperature higher than 15°C.
If your Buxus is badly affected, cut it right back and wait for regrowth. However, do not mistake the disease of the falling leaves of the Buxus with the ravages of caterpillars, the other danger for these shrubs.

The leaves are nibbled
The exterior of the Buxus looks fine, until you find the presence of caterpillars which nibble the leaves from the inside of the shrub and attack the outside leaves only at the end. These caterpillars are the snout moth of the Buxus. The big caterpillars and the cocoons are then highly visible and you cannot mistake this attack with the one from a pathogenic fungus, where the leaves fall without being nibbled. The bare stems stripped by the caterpillars will grow green again but some help is needed. Water it as soon as the soil is dry; give it some fertilizer between March and August. If the caterpillars are still present, you can stop their damage by spraying an ecological anti-caterpillars remedy (Bacillus thuringiensis ou BT), preferably in the evening.

The leaves are yellowing
In any season, the edge of the Buxus leaves can discolour as if the plant was variegated. This is not an ornament of the plant but the sign of stress at roots level. Frequently, this is the sign of an excess or a lack of water. Water more often (if the soil is dry) or improve drainage (if the soil is damp): Then everything gets back to normal!

The leaves become orange
Buxus grown in pots, more rarely those grown in the ground can become entirely orange. This is the sign of lack of water. As long as the leaves are not falling, the plant is still alive, as the Buxus is a drought tolerant shrub. But water straight away, keeping the soil damp until the leaves turn green again (this takes about one week). During that time, do not give fertilizer. Then, ensure that the shrub does not lack of water.

The leaves become deformed "spoon-shaped"
The symptoms are very simple: the foliage blisters, especially at the end of the branches. This phenomenon is seen on Buxus with large leaves. This distortion is caused by harmless, microscopic bugs. There no need to treat! In humid weather, the young leaves which form are incidentally, totally normal.
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This evergreen shrub can have a few worries, especially with the appearance of new diseases. However, good cares should keep it looking great! Spot the symptoms and act at the right time and the right way.

Author: Jean-Michel Groult
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