Getting to grips with garden pest control

PUBLISHED: 10:58 30 August 2018 | UPDATED: 12:16 30 August 2018

White flies are a common garden pest which reproduce quickly.

White flies are a common garden pest which reproduce quickly.

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Pests and diseases are threatening our gardens more than ever before - but what should we be looking for?

Earlier this year, the Prince of Wales issued a stark warning about the threat to UK gardens from pests and disease.

“The biggest fear is that we end up with a wasteland here,” he told Adam Frost on BBC Gardener’s World. He recalled the earlier epidemic of Dutch Elm disease and described the “multitude of threats” that our gardens face today.

And it is a concern which is shared. Last October, the Royal Horticultural Society banned nine imported plant species from its shows – including the prestigious Chelsea Flower Show 2018, which took place in May. According to notes circulated to trade exhibitors, only British-grown hebe, rosemary, lavender, oleander, olives, polygala, coffee, Spanish broom and prunus were permitted – unless they had been grown from seed in the UK or had been in the country for more than a year.

A bacterial disease called Xyllela is partly to blame, something that the Royal Horticultural Society describes as “one of the biggest risks to the UK horticultural industry and wider landscape.” It is spread by insects – such as froghoppers and leafhoppers – which feed on infected plants, and has now reached European shores.

But one of the main concerns about Xylella is that its symptoms – which include leaf scorch, wilt, dieback and plant death – can be easily confused with other diseases, or with the damage caused by frost or drought.

As a result, The Royal Horticultural Society has launched six new principles to help guide its activities across its gardens, shows and plant centres – and there are plenty of things you can do too, to ensure that your plants, shrubs and trees are fighting fit in the face of Xylella and other diseases.

Source plants effectively

It might surprise you to know that new plants – and their soil – are actually one of the most common ways to spread disease.

Find out where your plants come from and have a go at propagating your own. If you are buying from a garden centre, check with staff to ensure that your purchase comes from the UK – it’s the easiest way to avoid foreign diseases and pests.

Check, check and check again

Before you make a purchase, always check new plants for signs of disease. Keep new plants in an isolated area of your garden before planting them out and, once planted, check them regularly.

The Royal Horticultural Society website is a great resource for identifying problems.

Maintain health

Plants are a bit like us and the healthier they are, the better they will be at fighting infections and disease. So remember to check your plants for signs of ill-health, and treat them accordingly.

Mulching not only feeds your plants, but also prevents some pests and diseases from leaving the soil – this means that you can readily avoid infection further up the leaves. Keeping a clean and tidy garden helps, too – so clean water butts, green houses and garden tools regularly.


Dispose responsibly

Local green waste schemes compost at higher temperatures, which kills more pests and disease, while woody plants can be taken to a council refuse site.


Don’t know what you’re looking for, when it comes to pests and diseases? Gary Groucott from Wymondham Garden Centre shares 5 of the most common pests – and how to treat them.

1. Aphids

Tiny and translucent, these garden pests can infect just about every plant in your garden. Don’t let them fool you – they can spread quickly, as females give birth to live young.

Treatment: My favourite is to apply SB invigorator, which can be bought ready-to-use. It is a contact killer so must be applied all over the plant, but is environmentally friendly and safe to use around pets and children.

2. Caterpillars

These can be a major pest for all types of vegetables, so look out for holes.

Treatment: It is best to remove these by hand and destroy them. To prevent infestation, cover up plants with insect mesh. If it’s too late, use SB invigorator.

3. Whiteflies

These tiny white-bodied flies can often be found on the underside of the leaf. They are very difficult to control because they reproduce quickly.

Treatment: Systemic insecticides are best as they will protect the plant from within, but great care will be needed on edible plants.

4. Slugs

These might be your worst enemy, but they are essential for garden ecology.

Treatment: While there might be lots of slug killers on the market, they can be dangerous to birds, hedgehogs and pets. Placing grit or sand around the plants will help to prevent them from being eaten, but my favourite solution is to use any old or cheap beer! Pour some on a plant tray and the slugs won’t be able to resist.

5. Black spot

This is the most serious disease for roses which infects the leaves and makes the plant weak. It can be identified by lots of dark, black spots all over the leaves. If left unchecked, it will spread and the plant will start to lose its leaves.

Treatment: Infected leaves must be removed – and binned, not composted. The plant should be treated with a fungicide spray. Copper, lime sulphur, potassium or ammonium bicarbonate are some of the organic options available, but prevention is ultimately better than cure. Ensure the plant is not in damp conditions and is well ventilated with lots of sun.


For more inspiration, check out the digital edition of Beautiful Homes and Gardens.

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