How to keep the pests away

Hannah Stephenson reveals how to prevent - and deter - garden pests this autumn

If you haven’t killed off your garden pests this summer, some will carry on doing damage well into autumn, before emerging again in spring. Warm, damp weather gives many pests their perfect conditions, so you still need to be vigilant, clearing debris from containers which are past their best and could harbour pests, and disposing of old compost which could harbour soil-borne pests such as vine weevil.

Aphids can continue to thrive in autumn and then mate and produce eggs which overwinter, slugs can still munch through leafy crops during damp weather, while other pests can survive mild winters, only to emerge stronger and more numerous the following year.

Dr Anton Rosenfeld, knowledge officer for the charity Garden Organic, offers the following advice on the pests which can linger through autumn, and how to best deal with them…

CABBAGE APHIDS

“Although numbers slump in summer, they start to build up again in late September and can then become a problem,” Dr Rosenfeld says.

Normal measures – such as flowering plants (fennel, phacelia, buckwheat, limnanthes) to attract predators – are less effective at this time of year, as predators tail off in the autumn.

“A good jet of water can dislodge a good proportion of them. Soft soap sprays can be used as a last resort. Generally, as conditions cool, they become less of a problem from November onwards,” he explains.

BRASSICA WHITEFLY

Also known as cabbage whitefly, these can persist

right into December. They look unsightly, but generally can be rinsed off, and are only harmful when

infestations are extreme, but are often a problem in kale and Brussels sprouts. Choice of variety can help, for

example, flat leaved kale is less of a problem than curly leaf, he says.

PIGEONS

“Perhaps the worst pest over the winter, especially for brassicas, the solution is to keep crops covered, and if they get too large, string and sticks over the top stops the pigeons landing,” Dr Rosenfeld advises.

SLUGS

They are the bane of so many gardeners’ lives, especially in mild, damp weather.

Dr Rosenfeld explains: “Keel slugs are a problem in root crops, and grey field slugs can stop green manures emerging. There is no one magic bullet against slugs – use a combination of night patrols, growing plants to a larger

size, and using slug barriers. It is too cold to use nematodes over winter.”

VINE WEEVIL

Anyone who has ever had vine weevil in their pots will know the devastation they can cause, as the larvae feast on the roots of plants – but you often don’t see the damage until it’s too late: the plant suddenly wilts and you discover there are literally no roots left.

“Larvae will live in pots from late summer and through the winter, causing damage to the roots. Applying nematodes in August is best to prevent damage over winter, but if you’ve missed that slot, it can still work in April, to prevent them from being a problem next year. And a general principle to minimise all pests, clear away

leaf debris and any infested material where pests can overwinter,” Dr Rosenfeld advises.

AND IN GLASSHOUSES…

“As glasshouses are warm, pests such as whitefly, thrips and spider mites can survive in winter,” says Dr Rosenfeld.

“Give them a good clean – soapy water will work, or you can use citrox disinfectant. It is important to remove leftover plant pots and sweep up debris which will harbour pests. Bags of compost can harbour sciarid fly if left in a warm glasshouse, which can destroy or stunt your seedlings. It’s best to use fresh compost for seed sowing. Leftover bags should be well-sealed and used for larger plants, which are more resilient.”.

Mealy cabbage aphid is a greenfly with distinct whitish or ‘mealy’ appearance. They are sap-sucking insects that feed on cabbages and other brassicas.

Allium leaf minera are a big problem in many areas, but mainly ruin leeks. You need to cover crops in autumn to stop them laying eggs.

Red spider mites are a garden pest that attack a wide variety of plants, but most commonly damage azaleas and camellias

Vine weevil feed on a wide range of ornamental plants and fruits, especially those grown in containers

Slugs are a common garden pest, but they can be difficult to control

For many gardeners, pigeons are perhaps the worst pest over the winter