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The versatile Box Plant (Buxus spp) has long given even the smallest of gardens an extra touch of grandeur. Sadly though, your crisp-edged box hedge or topiary can quickly become brown, yellow or bare when obliterated by pests or diseases.
Box plants are very susceptible to disease which can wreak havoc on your shrub in as little as just one season and frustratingly, take years to recover.
Don’t worry though. By using specialist fertilisers and good plant husbandry, you can keep your box plant in tip-top condition and help it fight off pests and diseases before they take hold.
Boxwood Tree Moth/Caterpillar
Just as gardeners have started to get over Box Blight along comes another headache in the form of a pest called the Boxwood Tree Moth or more importantly the caterpillar. This beasty can cause untold damage to your plants in a very small amount of time.
How to Spot the Boxwood Tree Moth Damage on Box Plants
- The brown and white moth, which flies at dusk, leaves tiny fine webs across the plants.
- The green caterpillars are easy to spot having a black stripe down their back and spotted with black dots.
- Box hedge leaves look like lace as they have been eaten by the caterpillar
- Small caterpillar faeces.
- Extreme damage can be seen in March and September, spray as soon as you notice any damage.
How to Treat Boxwood Tree Moth/Caterpillar on Box Plants and Hedges
- The caterpillars do the damage, so remove them as soon as you can. These caterpillars rarely cause itching on your skin.
- Treat all infested and healthy plants within the vicinity with a caterpillar insecticide
- As good practice, treat the whole plant paying particular attention to the underside of leaves.
- Set a reminder to spray at the end of the summer and the end of the winter to catch the life cycle of this pest early.
- The problem can be treated biologically with Bacillus Thuringiensis. You can treat with a Chemical Caterpillar Insecticide but beware this is treatment is initially successful at killing the caterpillar but they will return!
- Stop the moth before trouble starts with a Boxwood Tree Moth Trap.
- Use XenTari Bacillus Thuringiensis to kill the caterpillar. This biological control stops the caterpillar feeding on the leaves within one hour and they die within 1-2 days.
I will make no bones about it, this really is a nasty one and unfortunately, there is no known cure. There are professional gardeners all over the UK pulling their hair out trying to fend off this vicious fungus.
That’s the bad news, now for some slightly better news. Box blight does not kill the roots so you have a fighting chance of keeping the plant alive.
Box Blight Diagnosis
- Leaves turn quickly from green to brown and then to grey as they wither and die.
- Sudden leave drop.
- Black streaks on the stems.
- White spores on the underside of the leaves (in humid conditions). If the spores are pink see Volutella Blight later in this post
What Can I do to Stop Box Blight Spreading?
- Avoid watering from above, the spores from the fungus are carried by water and this will only help to infect other parts of the plant, lay a hosepipe near the roots to water.
- The fungal spores thrive in wet, humid conditions so you need to get as much fresh air moving through the plant as possible, move the plant (if in a pot) to an open area of the garden.
- Remove any fallen debris from around the plant of the hedge as soon as you can. This will reduce the chance of infection to other parts of the plant or hedge.
- Spray with a fungicide, e.g. Fungus Clear Ultra. Although this will not kill the fungus it may stop it spreading.
TopBuxus have developed a health mix for box plant problems and it is incredibly effective. We used this specialised fertiliser on a badly infested hedge and the results were really quite impressive.
The fertiliser has various important elements which will build strength into the box plant and help with resistance to box blight, producing a far stronger plant.
The nitrogen will stimulate growth, whilst the magnesium and sulphur will help to produce green and healthy leaves.
The copper will aid the hardening of the cell structure of the leaves and stems, this will make the plant much more resistant to the fungal spores.
Below are some before and after pictures. I religiously followed the instructions of this intensive feed program and this was the result 4 months later.
Volutella blight is another Fungus related disease, thankfully not as devastating as Box Blight.
Volutella Blight Diagnosis
- Die back of twigs and leaves
- Leave drop is uncommon
- Pinkish spores on the underside of the leaves
What Can I do to Treat Volutella Blight?
- The fungal spores are carried by water and requires cuts or wounds to infect the plant. Avoid clipping early in the morning or in wet weather.
- Remove debris from below the plant
- Use a specialist buxus fertiliser, this will build a strong and resistant plant more able to fight off fungal infestations.
Discolouration of Leaves
The leaves of buxus plants can turn from pale green to bronze to yellow. These changes in colour are usually indicators of environmental issues which will put the plant under stress, for example, excessively dry weather.
Other Forms of Environmental Stress that may affect your box plants and box hedges include:
- Over watering.
- Under watering.
- Closed in court yards, creating a humid environment.
- Excessive shade.
Box plant roots grow near to the surface so if your plant is in a pot you could be over watering and the roots are sitting in water logged compost. If the weather is excessively dry, try watering little and often.
How to Look After Box Plants Summary
- Pests – Box plants suffer from caterpillar infestations. Spray with an insecticide.
- Disease – Buxus spp can suffer from serious fungal infections. Spray with a Fungicide to help your box plant fight infection.
- Feed – Use a specialist buxus fertiliser. There are a few available, containing nitrogen, magnesium and copper elements.
- Watering – Do not overwater. Box plant roots grow close to the surface so water little and often in dry weather.
- Don’t give up – Although box plants are susceptible to quite a few pests and diseases, they are strong versatile plants and can repay over and over, adding a touch of grandeur to your garden.
- Clipping – Try and get into a routine of trimming box plants and box hedges just before spring, the plant will hold its shape even after new shoots sprout in the spring.