Best Way to Control Pests in Your Vegetable Garden

The pleasure of growing your own produce can be short-lived if slugs or rabbits get to your crops before you do, and greenfly on a salad is rarely appetising. However, not every crop gets ravaged by pests and diseases each year. In most cases, using barriers to prevent pests reaching the crop, and keeping an eye on plants so you can tackle pest or disease outbreaks early on, are the only regular steps you need to take.

Barriers

Early in the year, a layer of garden fleece will protect young plants from flying insects such as aphids, carrot fly and cabbage white butterflies. Later, in the summer, crops under fleece can scorch, so use very fine plastic netting instead. Both are easy to use if draped over hoops of stiff wire, as this gives the crop room to grow. Weigh down or secure the edges so pests cannot get in. Crop covers can be washed and re-used but check them over for holes at the start of the season.

Not all gardens are afflicted with pests such as pigeons or rabbits, but those that are will need protection. Pigeon netting is draped over supports to protect overwintering crops. Rabbits can be kept out by installing a barrier of chicken wire fencing lm high above ground and buried 30cm below the surface.

Using pesticides

Pesticide is a term used to cover a number of products including fungicides that deal with diseases and insecticides that combat insect pests. As long as you follow the instructions, they are safe to use. Pay particular attention to the dilution rate, note which pest or disease they are recommended for and follow any advice on how long to wait before harvesting after spraying. Note that some pesticides are not suitable for edible crops or particular plants. Spray in the evening if possible to avoid harming pollinating insects.

You can buy pesticides in a ready-to-use form such as a spray gun. These are convenient to use but can work out expensive for a vegetable plot. Buying a concentrate that you dilute and apply with a pressure sprayer is more economical. Some insecticides are applied as a dust.

Organic gardeners prefer not to use pesticides at all, although some are used as a last resort.

Slugs and snails

A combination of vigilance and timely control methods should help to keep young crops safe from slugs and snails. Attacks are worse in the mild, damp periods of spring and autumn, and seedlings and young leafy crops are most vulnerable. Slug pellets are a popular control method as they are cheap and easy to apply. Gardening Which? trials have found them to be effective against slugs and snails. Nearly all slug pellets available to gardeners contain metaldehyde; this breaks down fairly rapidly, leaving very little soil residue. In addition, to limit the impact of slug pellets on wildlife, they contain an animal repellent and are colored blue to deter birds. Scatter the pellets sparingly around the plants and re-apply after two weeks, sooner if it rains. For anyone with a sizeable vegetable plot, the low cost of pellets compared with other treatments is persuasive: alternatives cost over eight times as much per square metre.

Liquid slug controls will kill the small black slugs that live in the soil and there are no visible pellets to worry about. One liquid, based on metaldehyde, worked well in Gardening Which? trials, but those containing aluminium sulphate work out very expensive for vegetable growing.

A biological control based on nematode worms was effective for six weeks against slugs if applied before planting.

Young plants can be protected from surface slugs with rings cut from plastic bottles. Cut sections 10cm high and push them 2-3cm into the ground.

A promising new barrier method is powdered Australian rock. It was effective in Gardening Which? trials when applied as a continuous barrier about 8cm wide. Copper tape is worth trying around containers or small raised beds.

An entirely organic method is to visit the vegetable plot at night with a torch. Collect any slugs and snails you spot; repeat the visits several times to reduce the slug and snail population.

Aphids

Greenfly and blackfly are just a couple of the 500 or so aphids found in gardens. All aphids breed prodigiously and suck the sap from plants. Plants are weakened, and the yield can be affected. In addition, some aphids spread viruses from one plant to another, for example, mosaic virus can be introduced into a courgette plant, with fatal results.

Most insecticides kill aphids either on contact or by being absorbed into the plant sap and killing aphids that feed on the sap. Alternatives are to rely on natural predators such as birds and insects to eat aphids, or to use a crop cover.