Hellebore diseases and pests

Aphids

Description and symptoms

These are the pests best known to gardeners. These sap-sucking insects attack both leaves and stems or flower buds. By feeding on hellebore sap, they gradually weaken the plant. Visible symptoms include leaf curling and reduced growth.

Above all, aphids secrete honeydew, a sticky substance which encourages the development of a fungal disease: sooty mould. This disease is easy to identify from the black, soot-like deposit that can be seen on Christmas roses. It affects the plant’s photosynthesis and can eventually cause it to die back.

Prevention

As a preventative measure, inspect your hellebores regularly so that you can take action as soon as the first aphids appear. The presence of ants, which feed on the honeydew secreted by these pests, is also an indicator.

Encourage biodiversity in the garden to attract aphids’ natural predators, such as ladybirds and lacewings. There are many ways to do this: install water points, make insect hotels, keep areas of fallow ground, grow wild plants, put up bird nest boxes and feeders, and so on.

Natural treatments

At the start of an attack, it is perfectly possible to remove the invaders by hand.

If the colonies are larger, you can use a homemade natural insecticide made with soft soap.

To do this:

• dilute 1 tablespoon of soft soap in 1 litre of lukewarm water;
• add 1 tablespoon of vegetable oil, such as rapeseed oil;
• pour the mixture into a spray bottle;
• wait until the insecticide has cooled before spraying it on the affected parts.

Apply this treatment early in the morning or in the evening, away from direct sunlight.

For further information: “Aphids: identification and treatment”

Green aphids on a hellebore flower

Black spot disease

Description and symptoms

This fungal disease is caused by a fungus (Coniothyrium hellebori). As its name suggests, it can be recognised by the black or brown spots it leaves on hellebore leaves. These spots are circular in shape and first appear along the edges of the foliage before spreading. The oldest leaves are generally affected first. However, if the disease spreads, for example in the case of an already weakened plant or a particularly damp environment, all the aerial parts may dry out. The hellebore will unfortunately eventually die back.

Prevention

Many simple steps can be taken to limit the development of fungal diseases.

• Provide your Helleborus with good growing conditions: naturally healthy plants are less prone to disease. Give them a partially shaded position in cool, organic-rich but well-drained soil (with good aeration so that water does not stagnate).
• Observe the correct planting distances between your plants, to allow natural air circulation.
• Do not plant Christmas roses in an area previously infected by a fungal disease.
• Always clean your cutting tools (pruning shear, scissors) before using them, to prevent the transmission of disease between plants.
• Avoid watering hellebore foliage. Moisture encourages the development of fungi.
• Quickly remove all plant debris that could encourage the development of spores (dead leaves, damaged stems, faded flowers, etc.). When the flower buds appear, remove the old leaves.

Natural antifungal treatments

If you notice the first symptoms of black spot disease, immediately remove the affected parts. Use a pruning shear and clean it thoroughly after use (with alcohol, for example). Do not put this plant debris in the compost, but take it to a waste recycling centre instead.

Against fungal diseases, you can use natural fungicides based on copper sulphate. The best-known is Bordeaux mixture. It is a product that can be used in organic farming. However, its use is not without consequences: in large quantities and when applied regularly, it can unbalance the soil and encourage the appearance of diseases. Use it sparingly.

If you would like to use even more natural treatments, opt for plant manures. Their effectiveness has not been scientifically proven, but many gardeners observe beneficial effects, both as a preventive and a curative treatment. Try nettle manure and horsetail decoction, diluted in water (ideally rainwater). Spray the affected parts, away from direct sunlight.

For more information: “Everything you need to know about fungal diseases” and “Bordeaux mixture and other copper-based treatments in the garden“.

Gastropods

Description and symptoms

We all know these small, slimy gluttons, which can cause serious damage in the garden. Snails and slugs feed on young hellebore shoots, and sometimes on the flower buds too. They can quickly finish off a young plant.

Prevention

There are many preventive solutions to stop gastropods feasting on your Christmas roses. Some gardeners use beer traps, while others prefer natural physical barriers made from ash, eggshells or diatomaceous earth.

Natural treatments

You will find ferramol-based products in shops or online, suitable for use in organic farming, to control snails and slugs. The pellets consumed by gastropods act as an appetite suppressant and cause them to deteriorate.

Collecting the unwanted visitors at nightfall can also prove effective. It is a 100% natural and free solution, but it is time-consuming.

For more information: “Slugs: 7 effective and natural ways to control them“.

Gastropods are fond of hellebores