NOW is the time to be enjoying the fruits of your labour in the sunshine, when your containers and hanging baskets are planted, the sweet peas are shooting up the canes and your bedding plants are coming along nicely.

That is, until some unwelcome visitors come out for a feast - and we're not talking about your neighbours. The culprits are aphids - greenfly, whitefly, blackfly and a host of other sap-suckers which can multiply on your blooms in a short time.

The black bean aphid (Aphis fabae) forms dense black colonies on broad beans, artichokes, dahlias and nasturtiums while the grey-white mealy cabbage aphid (Brevicoryne brassicae) lives in brassicas, mostly cabbages, and swedes. Some rose aphids are pink in colour and will gather on flower buds and stems, reducing the quality of the flower.

While singly, most aphids are pretty harmless, their numbers can increase enormously almost overnight and en masse they can quickly reduce the strength from a plant as they congregate on the flower, leaves and stem, feeding off the sap. Some aphids even feed off the root and you may not discover that until it's too late.

It's fairly easy to spot the symptoms, as green, white or black aphids cluster on flowerbuds, leaves and stems. Black sooty mould, which grows on the honeydew the aphids secrete, will start to appear on the lower leaves.

They are also extremely fond of apple trees and if you get an infestation, you will notice the trees' leaves curling.

They multiply at a frightening rate, giving birth to live young in spring and summer and, as temperatures drop in the autumn, they lay eggs which will overwinter. The live young can go from nymph to adult in just seven days.

While aphids may lead to a weaker plant and poor blooms, they can also transmit virus diseases from one plant to another. Sweet peas and raspberries are extremely susceptible to these diseases and once you've noticed the symptoms of mottled leaves it's best to remove the infected plants completely rather than risk other neighbouring ones contracting the disease as well.

Of course, there are many insecticides on the market which will kill the aphids. If you have a small garden, it's probably better to use the ready-prepared insecticide which comes in a spray and should blast the aphid on contact. If the problem is more widespread and you have a big area to cover, go for the concentrated insecticide which has to be diluted and then applied with a fine sprayer.

Other remedies contain systemic chemicals which should alleviate the problem for a longer period of time.

Luckily, aphids do have some natural enemies. Ladybirds and hoverflies prey on them, while solitary wasps feed them to their larvae. Bright flowers, particularly in purple and yellow, attract hoverflies and may go some way to stop the aphids multiplying. Lacewings and many types of bird also help stem their growth, while the larvae of midges eat aphids and the larvae of parasitic wasps develop inside the aphids' bodies.

Be careful if you are going down the chemical route to zap these invaders, because you may also be damaging the many other insects beneficial to your garden who are the aphid's natural enemies. If you go for a general insecticide which will kill all insects in its path, try to spray at dusk when fewer beneficial insects such as bees are present.

However, you can buy pesticides, such as Pirimicarb, which will control your aphids but have little effect on other pests.

Happy zapping! Nicotiana -- plant of the week THERE is nothing more pleasant of a summer's evening than to venture into a garden away from the city smog and breathe in the deliciously sweet scent of the summer annual, nicotiana, otherwise known as the tobacco plant. These reliable bedding plants require little maintenance except that they are grown in a reasonable soil with lots of moisture, and will flower until October if you deadhead them regularly. They will even thrive in light shade. Grow the N. alata for its wonderful evening fragrance, white flowers and long flowering period. In years gone by, nicotiana was a tall plant which needed staking and only opened its blooms in the evening, but now there are smaller varieties and many hybrids whose trumpet-like flowers stay open during the day, although I don't believe they have as much scent.

Of the more compact, bushy varieties, try N. sanderae Domino Series Salmon Pink, which flowers all day. For an eye-catching change, N. alata Lime Green is also popular, producing yellowish green flowers. Alternatively, try Red Devil, which grows to 3ft and Nicki Mixed. White borders will benefit from an injection of the fragrant, tall N. sylvestris. Nicotiana should be sown in warmth in spring, pricked out into trays and then planted out after the last frost. And beware of buying mixed trays of them - because you may end up with some non-scented specimens.

GARDENING CHORES THIS WEEK'S WORK OUTDOORS Water hanging baskets daily and deadhead regularly for a longer flowering period.

Tall sunflowers need to be staked to canes for support.

Pull up earth around potatoes to promote better tuber production.

Continue to plant summer bedding where there are gaps in your borders.

Mow lawns once a week.

To avoid scorching plants, cover the greenhouse's south side with shade netting or blinds.

Mist over cucumber plants in the greenhouse to keep humidity high.

Cut back long shoots on wisteria to around 12in.

Cut foliage from strawberries that have finished fruiting.