Anna Pavord's A to Z of pests and problems: M is for machinery, mealy bug and mildew

Do you really need that hedge-trimmer? And how to tackle moles. Anna's essential A-Z continues

Downy mildew proliferates in damp conditions, on wet foliage with too little air moving round it. (Alamy)

Machinery

You either love it or you hate it. Either way, beware the attitude that once you have bought the machine, you have done the job. Hedge-trimmers need to be given outings, though they are painful to operate. Strimmers need to strim, though the noise is excruciating and the line will keep disappearing up the handle. If you have a lawn, a mower is essential.

The need for any other machinery should be carefully evaluated before you buy. Some jobs, such as hedge cutting, are so seasonal that you might find hiring a more economical option. Then if the machine does not work, you can take it back rather than kicking it.

Mealy bug

This is a tropical pest that attacks house plants and greenhouse crops as diverse as cacti, fuchsias and orchids. It is easy to recognise. The bugs are small and white and give the impression of being covered with a waxy looking wool. At all stages - adult or larvae - they are a nuisance. They feed on plant sap and excrete a sticky liquid which, in turn, attracts sooty moulds. They usually sit round the crown of a plant, tucked into leaf axils and in other places where it is difficult to dislodge them. In suitably cosy conditions they will breed all year.

The chemical solution is to spray with an insecticide such as Provado Ultimate Bug Killer, but you may have to repeat the treatment two weeks later. If they are not too widespread, pick off the mealy bugs with a dry paintbrush or one dipped in methylated spirit.

There is also a biological control, a black and orange Australian ladybird called Cryptolaemus montrouzieri, which eats mealy bugs and lays its eggs inside them. It eats prodigious numbers however and then, if it runs out of that fodder, may start to eat other ladybirds.

Mildew

Prevention is better than cure. Which is the kind of remark maddeningly self-satisfied (and mildew-free) gardeners make as you stare at a crop of lettuce, unappetisingly rotting before your eyes.

There are two different kinds: downy mildew which may attack brassicas, grapevines, onions, and spinach; and powdery mildew which may go for gooseberries, apples, peaches, plums, rhododendrons and strawberries. Some plants - lettuces, peas and roses for instance - can get both.

Both are types of fungi, and spread by rain or wind. Downy mildew can affect plants all year round. Powdery mildew is most prevalent from summer through to autumn, though it can appear in spring if it happens to be an unusually dry one.

Downy mildew proliferates in damp conditions, on wet foliage with too little air moving round it. In greenhouses you should get rid of dead and dying foliage, which attracts mildew. Powdery mildew is often the result of a plant being too dry around the roots. So by getting the growing conditions right, you can cut down on the chance of mildew descending.

If it does, bear in mind that once you start using a fungicide (such as Scott's Fungus Clear Ultra) you'll have to go on applying it every three weeks. And though a fungicide may contain a mildew attack, it cannot cure it.

Millipede

It's a Trivial Pursuit question - why is a millipede not a centipede? Because it's got two pairs of legs on each segment of its body. Centipedes have just one and are the more useful of the two, as they gobble up soil pests. Millipedes go for plants, such as strawberries and potatoes, though most often they are merely following on from slugs who create far more damage. Putting straw under strawberries helps protect them from both.

M is for Mole

I once ran a competition in my column to find the best way of ridding a garden of moles. The difficulty lay in discovering a method that had proved infallible.

A suggestion put up by one reader would be slapped down by the next, who put up a different one, only to be shot down in flames by the experiences of the third - and so on. Several readers suggested burying empty bottles in the runs. The noise of the wind blowing over the tops of the bottles is supposed to unnerve moles, but as many as recommended this trick said that it did not work.

Muriel Georgopoulou, a "vicarious gardener" in Athens, suggested stuffing mole runs with onions, but Major MacRae of Blairgowrie had already tried them and found them wanting. Mrs Eaton of Pitscottie in Fife found an old recipe involving a soured mixture of whey and buttermilk to pour in the runs. "The smell is supposed to do the rest," she said.

Deterrents seem to depend on which of the mole's senses you feel to be the most susceptible. Some suggested burying the tune mechanism from a musical greetings card. Others felt a few hours of Radio 1 or 2 each day would do the trick.

Paul Dunwell-Schwyter from Switzerland recalled a "sobering demonstration" by his father of the effect that a Lambretta SX 200 can have on moles. "You park the scooter beside the freshest run and rev up the engine while in neutral. It's not even necessary to give it full throttle to achieve the desired effect", though whether it was the noise or the fumes that did the trick, he does not say.

Creosote and Jeyes Fluid featured in several reader's accounts. Creosote plus old socks was infallible in the experience of Ms Shenstone of Coventry. Jeyes Fluid followed by a hosepipe flood was the preferred method of John Clarke of Bury St Edmunds.

Flooding certainly shifts moles in situ, as I've found myself. But then they come back… In the absence of any one totally foolproof mole deterrent, I gave the promised prize bottle to Leslie Jerman of Epping in Essex for a brilliant treatise on methods of discouraging moles. His neighbours, he said, had tried mothballs, paraffin, creosote-soaked rags, cods' heads, smoke bombs, wine bottles and spurge plants, all to no avail.

Fakenham racecourse, said the encyclopedic Mr Jerman, had ordered a thousand spurge plants to save the expensive fetlocks of its racehorses. But they did not trouble the moles one little bit.

He also described an experiment by the Ministry of Agriculture, coating worms with gum acacia to poison moles, but the moles scraped off the gum by dragging the worms through their feet. Mr Jerman also passed on the name of the last man in England to make moleskin waistcoats, Cyril Barnett of 54 Bartholomew Close, London EC1. He retired in 1990.