BIOLOGICAL PEST CONTROL

Environmental damage brought about by our use of chemicals in every sphere of our lives, is being felt by every living organism on the planet. Many of us are now trying to redress the balance by using some form of organic pest control in our gardens and in our agricultural practices rather than relying on harmful pesticides. All of us with gardens no matter how small, even those with terraces and window boxes, can contribute to a healthier environment by controlling our garden pests naturally, and there are quite a number of surprisingly effective ways of doing this. Here are some examples of how to keep your garden pest-free organically:

• Ladybirds (or ladybugs) are the natural predators of plant-sucking insects such as fruit flies, thrips and aphids (greenfly or blackfly) the particular enemy of rose growers. You can buy ladybirds from specialist garden centres. (If you also use black liquid soap for aphid, be careful how you apply it as this can also kill your ladybirds.)

• Praying Mantis. These fascinating insects will eat almost any garden pest and will control flies and mosquitoes. You can buy their eggs from specialist garden suppliers.

• Frogs and toads are excellent controllers – particularly of ants, but if you import these into your garden, remember that, they are amphibians and need access to clean water and a moist environment, and with their porous skins, are highly susceptible to chemicals. A certain amount of precaution is needed with these animals. If you buy them, avoid using the Internet and make certain they come from a reputable source otherwise you could end up with your controller becoming the pest, as has happened with the Australian cane toad.

• Birds. All small garden birds should be encouraged; they all contribute to keeping your garden slug and caterpillar-free. It is true that they too can be annoying pests when it comes to strawberries, cherries and other fruit crops! But there are perfectly humane and practical ways of dealing with this problem. And yes – a good old-fashioned way is the scarecrow. Birds hate them. They are easy and fun to make and can involve the whole family. Using nylon netting can also be very effective but it is not the greatest method as birds can get horribly tangled and die.

• Beneficial nematodes which are minute worm-like organisms which are harmless to humans, animals and birds, but which control such pests as leather jackets, which are the larvae of Crane fly (or Daddy long legs as they are known in UK), Vine Weevil and Slugs. These too can now be bought by individual gardeners at specialist shops.

However, as in agriculture, a natural pest controller such as the ladybird or praying mantis, will only operate if their particular food is available, otherwise they will move away to richer pastures!

Nematodes

Nematodes are the most profuse multicellular organisms on earth. There is virtually nowhere on this planet that they can't be found and they are quite literally everywhere in your garden. There are an estimated 500,000 to a million species of which 20,000 have been identified. They are generally a microscopic (though they can grow to a length of eight metres!) non-segmented type of roundworm which can be divided into three categories, parasitic, predaceous and those that live freely in the soil. In human terms there are ordinary nematodes, bad nematodes and good nematodes. In general they are specific in their habits

• The ordinary nematodes are the equivalent of the 'ordinary-man-in-the-street' and feed on bacteria and fungi in the soil. But they are not to be underestimated as the help to break down organic matter.

• The bad nematodes attack the roots of plants and can also be parasites in humans and mammals. (One way to control parasitic nematodes on your plants is to intersperse your planting with marigolds, which have a deterrent effect.)

• The good nematodes, which are being used more and more as an alternative to chemicals, are proving to be just as effective for garden and agricultural pest control.

The beneficial properties of nematodes have been studied for several centuries. There was an interest in their use against Japanese beetle in the early part of the 20th century, but this soon gave way to the universal deployment, in gardens and on crops, of the cheaper, more readily available chemicals. Now, of course, there is a very strong, renewed interest. Laboratory studies are intensive and nematodes are being used more and more both in agricultural and domestic use. Various nematode species are used depending on climate and the type of pest which has to be controlled, and they operate passively or actively. The passive nematodes at the top of the soil lie in wait for their unwitting prey such as snails and slugs cutworm and leather jackets, predaceous nematodes, which are found deeper in the soil, actively hunt for their prey.

There are various species of nematode available commercially; the two most commonly used are likely to be Heterorhabditis bacteriophora, to be used against pests such as vine weevil, weevils and other beetle grubs and Steinernema feltiae, used against fungus gnats and various flies, amongst others.

Nematodes are deployed in much the same way as ordinary insecticides. They are packaged in different ways and are mixed with water and either sprinkled or sprayed. Nematodes are live creature and have to be protected from dehydration, they should not be left for an indefinite time in the spray tank, spray pressure should not be excessive and to avoid too much UV exposure should be sprayed in the evening.

Common Pests in Your Garden

The vine weevil is a really pernicious pest, commonly found in container plants such as fuchsias, cyclamen, begonias and primulas, but have become less fussy in their eating habits and can be found in other plants too. A vine weevil's eggs are too small to be seen without a lens, but the grubs can be up to

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