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How to repel insects and pests naturally

Andy Hamilton

1st May, 2009

Insects can be a double-edged sword when it comes to gardening. Andy Hamilton reveals the secrets of harmless, low-impact repulsion.

Whether eating our plants, biting our children or just buzzing around our living rooms, insects can be less than welcome visitors. However, as they are the pollinators, silk producers and recyclers of the Earth, we need insects for our very survival. This is why we should turn to nature’s biological controls to repel them, rather than target one sort and risk killing them all, even the most beneficial.

Mothballs au naturelle

Last year we received an unexpected present with some of our whole foods: a clutch of moth eggs. Once hatched the larvae made short work of our food as they systematically munched through much of our dry goods. Not content with destroying our food they quickly moved on to the bedrooms and tried to make a home in our clothes. Something had to be done before my wardrobe had more holes than the banking system.

In the kitchen we started with a two-pronged attack. First, we made sure that everything was stored in glass jars with airtight lids. Like all living things, moths need food – no food, no moths. I also cleaned the cupboards with lavender oil, which helps repel them. In order to aid its own survival, lavender (along with some other plants such as eucalyptus and lemon grass) has evolved to emit smells and substances that moths hate.

Next, to protect the bedrooms, I made my own mothballs. For these I cut up an old, moth-eaten (I kid you not) shirt into two 10cm x 10cm squares, sowed them together and filled them with a couple of bay leaves, dried basil leaves, some spearmint, thyme, tansy, rosemary and wormwood. All of these herbs are used to repel moths for the same reason as lavender. This really works, but it can lose some of its potency in time and is therefore best replaced every six months or so.

For added protection you can make a hot infusion from some or all of the above herbs. Simply stuff into a teapot, pour on boiling water, allow to cool, strain, decant into a spray gun and spray as required.

A quality repell-ant

I stayed on a Spanish island for a while one summer and noticed, when cooking, that if you left any food around you were soon infested with ants. It is a point worth reiterating that, as with all living things: no food, no pests. They can be pretty stubborn, though, and to deter them further there are other methods. Many ants are not too enamoured of some herbs, including sage, peppermint, tansy, catnip and pennyroyal. Either grow these plants by your kitchen door or make an infusion spray as above.

Equally, bicarbonate of soda, coffee grinds, chilli powder or flour are all reported to work. I have had good results on the allotment sowing seed mixed with chilli powder to stop the ants nicking the seed.

Although I tend to work around the ants on my allotment, occasionally I will dig up a nest if it is close to what I need to plant. It can be quite interesting watching them pick up their belongings and move house to somewhere else on your plot.

The mosquito’s toast

As our country gets wetter and warmer we can expect to see numbers increasing.

With more than a million deaths annually attributed to mosquitoes, they can be more than just an irritation when you’re abroad.

Untidy gardening can attract mosquitoes; if I’m not careful my back yard can soon become as full of them as the Everglades are. Less than 30ml of water in an open container is enough for as many as 300 eggs. Prevention is better than cure, so ensure you don’t leave out buckets, old plant pots or anything else in which water can collect.

If on holiday you’re being troubled by the little blighters then you can repel them with feverfew. Take a few leaves with you and when needed leave them to infuse in hot water, allow to cool then apply to the exposed areas of skin. Crushed garlic blended in water can also be applied but it will pong a little more. One of the most pleasant (and thought to be the most effective) plant-based compounds used for repelling mosquitoes is citronellal, which can be found in lemon balm. To administer, crush a few leaves and rub on to your skin.

You may also notice that you don’t get bitten as much as your friends (or vice versa). This could be down to nutrition or immunity. If you don’t get bitten that frequently it may be due to your diet – if you’re bitten a lot then try to improve your diet. High levels of zinc and vitamin B complex can help keep insects away. When I awoke on holiday, bitten to shreds, I used to put it down to sugar in my system, but many of the vitamin B complex vitamins can be dramatically reduced when drinking alcohol, so it was this that was likely attracting them. Therefore, it should be a consideration to supplement your diet if you intend on having a boozy holiday.

Bye-bye, greenfly

Bob Flowerdew once said on Gardeners’ Question Time that jam is a great deterrent for greenfly. As obscure as it might sound, a dollop of jam next to your prize beans will stop the ants harvesting the greenfly for their honeydew excreta. Because ants farm greenfly for their sweet asting excreta, when they taste the jam, so the rationale goes, they say to themselves, ‘that tastes great – better make sure the greenfly don’t eat it’. They then start killing the greenfly to stop it happening, which is nothing short of genius.

Compost and fruit flies


Those of you who have little choice but to collect compost indoors might come into contact with fruit flies and the smaller compost flies. Once these little pests have set themselves up in your house it is not so much about repelling them as eliminating them. Wetting newspaper and putting it over the top of your compost in the main bin will help to stop them from breeding, but this is not something to do frequently as it will interfere with the composting process. My favourite way of tackling them indoors is with a carnivorous plant, which, as the name suggests, eats the flies.

If you do decide to get yourself a carnivorous plant then it needn’t be the freakish-looking Dionaea muscipula, also known as the Venus fly-trap. It could be something far more beautiful such as Nepenthes distillatoria, known as a pitcher plant. These plants can be bought from many specialist florists. They work wonders in keeping the fly population down but can be a little disturbing when you hear a lone fly slowly decomposing while buzzing its final buzz. Not for the fainthearted!

 



Andy Hamilton is co-author of The Selfsufficient-ish Bible: An eco-living guide for the 21st century (Hodder & Stoughton, £30)

 

 

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