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Pesticide use in greenhouse and garden bugs me

By West Briton  |  Posted: October 18, 2012

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THE summer greenhouse cropping season is over, the light levels are starting to drop and what a sorry sight my tomato crop is now.

It's time for the students to clean it all out ready for winter greens. This is always a sad time, as, in the name of crop hygiene, we have to get everything as clean as possible which means using chemicals.

But not only do these kill off any pests and diseases they also destroy all the bio-control introduced over the summer. Bio-control are specially selected beneficial insects brought into a greenhouse (or garden) to deal with aphids, spider mites or other pests.

This got me thinking about pesticide use elsewhere and the many ways we can attract and encourage nature to do the job for us.

Know your bug. Beneficial insects are divided into predators, parasitisers (sic) and pollinators. Predators, like ladybirds, hoverflies and ground beetles, eat pests. Larval ladybirds are just like teenagers. They eat everything in sight but are your best friend for aphid control. Parasitisers such as braconid and ichneumon wasps lay eggs inside the body of their prey as food for developing larvae. When the larvae matures, out it pops leaving its host an empty shell. It's a bug eat bug world in your garden, it really is.

There is no need for chemical insecticides in a well-managed garden and now is the time to think ahead. Many beneficial insects will be looking for somewhere to over-winter, so build them a cosy home. Several layers of logs and twigs laid at right angles covered with a layer of mulch will do the trick. It will remain a suitable temperature inside all winter long.

Then the next step is keeping them in your garden when they emerge, hungry and thirsty looking for nectar, pollen and water.

To do this you need an insectary. This is an area where there are suitable flowers to attract and keep beneficial insects all through the spring, summer and autumn months. The key here is diversity, giving them nectar and pollen as well as cover in which to hide. Early spring flowers like celandine give way to yarrow and umbellifers like wild parsley and carrot. Most predators are attracted to flat, open yellow or orange flowers as this says: 'land here, it's really good'. Marigolds, nasturtium and tansy flowers are good for this.

Like all living things they need water. Shallow pools are ideal, even a saucer, kept well-filled with clean water with a few pebbles in the bottom to prevent drowning, will do the trick. Even just turning the hose on from time to time keeping a few puddles will help.

Beneficial insects do not become pests themselves since they are programmed by nature to adjust their own population to fit those of the pests. And the happier you keep them the less chance you have of losing them to next door or the wide world beyond. Keep them happy and they will reward you handsomely.

So what about the wider picture? Wider, that is, than our college or your garden. Out in the landscape of Cornwall, particularly the 30 per cent designated as an Area of Outstanding Natural Beauty, balance is everything, indeed crucial to our very survival.

Our natural resources exist in a delicate balance and are vulnerable to environmental changes, particularly man-made ones. That's why it's so important that we all do our part to conserve and care for our resources – and protect the environment that sustains us with food, water, fuel and shelter. The debate about pest control is one about our whole environment in a microcosm.

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