How to deter unwelcome summer guests

Those who love both herbs and detective stories will have noted that the ethical detective writer either leaves out an important step in producing the poison - Agatha Christie once implied that her villain used an innocuous part of an otherwise potentially deadly plant - or, like Pugilisius Mugwortium, creates a weapon entirely from their own imagination.

(I was once placed next to a doctor at a dinner party whose hobby was collecting ways to undetectably murder people. Despite my assuring him many, many times over that I didn't write that kind of book, he insisted on giving me the details of all his researches. In forty-odd years of study he'd only come up with one 'probably' foolproof method, and even that would depended on the ability to seem innocent and a great deal of luck.)

I met my first unwelcome summer visitor yesterday, and promptly exterminated her. She was a mosquito, trying to find her way through my tough long-sleeve shirt, and so intent that she didn't notice when I yelled "gotcha!" Mozzies are easy to kill, if you are prepared to spend your entire time swatting. It's better to make sure they don't breed nearby, in the still water in the saucer under your pot plants, for example, a ridiculously popular place for mozzie breeding grounds. Empty and clean the dog and birds' water dishes each day. (This is also far healthier for the birds and dogs). Encourage frogs - and mozzie eating tadpoles - by refraining from using pesticides, fungicides or poisons in your garden. When it comes to mozzie murder, frogs are your friend. So are lizards.

Otherwise stick to a DEET-containing repellent, though I tend to put it on my clothes, not my skin. Include a DEET-scented a scarf in your "eating out of doors" outfit, or for gentlemen, perhaps a cravat. Citronella candles have only a mild deterrent effect - citronella is used because it grows fast and so is cheap, not because it's the most mozzie-repelling plant oil. A combination of lavender oil and lemon eucalyptus oil can be repellent - it may well repel any human too - but will leave stains on your clothes.

I'm often asked what to plant to repel mozzies in the garden. The oils from catnip, lemon-scented gum, Backhousia myrtifolia, cedronella, lavender and several other plants repel mozzies, but even if you sit on a lavender bush - which will do the bush no good at all - surrounded by catnip plants, they won't release enough scent to disguise the odour of a warm-blooded human from mosquitoes.

Ants are similarly unwelcome. It's a pity that the "last resort" Christmas gift of scented talcum powder has gone out of fashion. Ants hate it. But a mix of baby powder and white pepper will create a barrier ants won't cross. If ants invade your house or garden furniture, polish lavishly with peppermint oil or essence. I didn't believe this would be effective till I tried it.

The flies you find a nuisance are probably either after your tucker or the moisture in your eyes. We have a collection of mosquito net tents, some large enough to cover the turkey that isn't on the menu this year, and some small enough to cover a jug of fruit punch, so food can be kept safe from flies, wasps and bees on the garden table or picnic rug. They are an excellent investment.

You can make your own fly traps with a soft drink bottle, cut at the shoulders and the top inverted to make a funnel, and a bait of six prawn heads, two beaten raw eggs, a teaspoon of sugar, a pinch of yeast and half a cup of water. Hang somewhere high so the stink wanders upwards and attracts the flies, instead of disgusting your visitors. They really do make a difference to fly population, and also attract an excellent holiday feast for any fly-eating birds who learn to hang around the top. Compost the contents.

If you have flies in your eyes, your hat brim isn't big enough. I used to go fishing with dad. I wore a wide-brimmed, elegant - if slightly tatty - straw hat, and had no flies in my eyes. Dad wore the kind of orange towelling hat that only dads of his era wear, and was fly ridden. But he still wouldn't give up his hat.

Basil is the best fly repellent plant I know. Electric fans can also help - only determined flies and mozzies will fly into a strong headwind. But sadly for a garden writer, the best pest solutions I can offer are not botanical. Cover up exposed skin and exposed food, and wear a wide-brimmed hat. Forget the fashion for baseball caps, blokes. Bring back the broad-brimmed melanoma-reducing Akubra.