Whitefly are small white flies which lurk on the undersides of leaves of many plants indoors and out. They rise like a cloud of cigarette ash when you touch the leaves. Spray the plants with a preparation which contains dimethoate to combat them.

Birds eat the blossom buds on fruit trees, then the fruit itself, also the leaves of cabbages and lettuce. Use the net covering to thwart them when this is troublesome.

Earwigs are a pest where dahlias and santhemums are concerned eating the leaves and flowers. Dust the plants with lindane, BHC or sevin dust, the surrounding soil too.

Scab causes those black blotches on apples and pears. Prevent this by spraying with something containing captan during and after flowering.

Blackfly not only damage the tips of shoots on beans, nasturtiums and other plants but they tend to spread virus diseases. Spray them with a preparation containing dimethoate.

Broad beans which are autumn-sown are less vulnerable to black fly than those started off in the spring since their growing tips are tougher and less attractive to those pests.

Botrytis is easily recognised as the grey mould on strawberries, lettuce and greenhouse tomatoes. Dust them with a preparations containing dichloran.

Cabbage root fly, caused by maggots eating the roots, shows above ground by wilting leaves which turn blue at the edges. Dust the plants with a preparation containing lindane.

Carrot fly makes the leaves of carrots and parsnips turn red or yellow, and the maggots ruin the roots. Prevent this by forking naphthalene along the rows of young plants.

Caterpillars eat irregular holes in the leaves and stems of many plants. Spray them with pestkiller containing carbaryl or use sevin dust.

Frog hoppers make “cuckoo spit” on young leaves and shoots. Dust or spray them with derris to prevent this.

Guard against club root, which makes the roots of cabbages, cauliflowers and other brassicas swell and the plants wilt. Use calomel dust when you plant them.

Leaf hoppers are small green insects with pale larvae which suck the juice from the leaves of many plants. Derris dust is the best deterrent.

There are two kinds of mildew- powdery and downy- which can affect plants. Powdery mildew looks like a white dust on the leaves and fruits of many plants. Prevent it from forming by dusting with powdered sulphur once a night in summer. Downy mildew appears a light powder on the underside of leaves, particularly grape vines, which then turn yellow. Spray affected plants with a preparation containing zineb.

Pea and bean weevils nibble pieces out of leaf edges. Dust or spray them with derris.

Those maggots that you find in pea pods are those of a pea moth. To avoid this problem, spray your pea plants with derris just after they have flowered.

The small white grubs in raspberries, loganberries and blackberries are the work of the raspberry beetle. Use derris again to deter them, dust it on the fruit just as it begins to ripen.

Red spider mites are tiny red or yellow spiders which suck the juice of the leaves of many houseplants. They are too small to be seen with the naked eye, but if you rub the undersides of affected leaves you may see some fine red dust on your hand. Spray affected plants with derris.

Scale insects attack houseplants too, and can be spotted as small brown limpet-like bumps on the undersides of leaves and on stems. Wash as many as possible off the plant in a warm soapy solution, then spray it with something containing diazinon.

Mealy bugs are a curse that often affects houseplants, oval insects covered with white wax which suck the juice from leaves. Dust the plants thoroughly with derris or malathion and isolate the affected plants.

Sooty cloud is another house plant disaster. It appears s a brown or black patches on the leaves of plants. Spray them with malathion or diazinon.

Thrips are another indoor pest, small insects with four wings which cause distinctive silver streaks in the leaves of many plants, mottling and distortion in others. Spray affected plants with BHC/lindane based preparations.

To make sure that you dose houseplants thoroughly with pesticides or fungicides, and to avoid unpleasant smells around the house, spray the plant out of doors on a still day if you can, or in the garage, and upend a bucket or a plastic waste sack over the plant immediately afterwards, leaving it in place for an hour or so.

Rose sawfly makes the leaves of roses curl up. Take the leaves off, and burn them immediately.