Controlling Garden Pests and Diseases

Controlling Garden Pests and Diseases

Once you decide to encourage wildlife into your garden, you must stop using pesticides, fungicides and weedkillers. Pesticides kill the good insects as well as the pests; slug pellets kill hedgehogs; and fungicides and weedkillers affect earthworms. Initially this may lead to infestations of greenfly (aphids) on the roses, but once the ladybirds, hoverflies and lacewings have increased in numbers, they should keep the greenfly at an acceptable level.

Controlling Garden Pests and Diseases A healthy, well-grown plant will tend to be unaffected by an infestation of greenfly or an attack of mildew, and will grow away quickly from any damage. Always grow plants that are suitable for the soil in your garden, and place them so that they get the right amount of light and moisture. Enrich your soil with as much organic matter as you can find, whether it is garden compost, leaf mould or spent mushroom compost, and add well-rotted farmyard manure in place of artificial fertilizers. An organically rich soil will feed the soil micro-organisms and increase their activity. It will also supply the plants with a balanced range of nutrients and encourage root growth.

Hints and Tips

Do not lose heart in the early stages if pests seem to be thriving – it takes time to achieve the right balance.

Always destroy infected plant material, so that diseases cannot be transmitted to other plants via garden compost.


The next stage is to encourage natural predators that feed on the pests. Ladybirds and their larvae, hoverfly larvae and lacewings and their larvae all eat massive amounts of aphids, so planting flowers whose nectar attracts these predators will bring these useful insects into the garden. Frogs, toads and magpies eat slugs, so a garden pond will provide a place for the frogs and toads and nearby tall trees a nest site for magpies. Hedgehogs also eat slugs, so providing places for hedgehogs to hide will help control slugs. (Note that, because the pellets we put down to kill slugs also kill hedgehogs, natural control of these pests is thwarted by our intervention.) Many birds eat insects and caterpillars, so creating a range of habitats for different birds will be a help in keeping insects and other pests at an acceptable level. There will always be a few pests, or the predators would go hungry and might die out themselves; it is a question of achieving an acceptable balance. After all, a few holes in the lettuces is a small price to pay to ensure the safety of all the inhabitants of the garden.

Other methods of controlling pests include companion planting — planting two plants together, where one of the plants controls the pests or diseases of the other. Planting Tagetes patula (French marigolds) in the greenhouse can reduce whitefly infestations, and planting strong-smelling alliums next to roses may reduce blackspot. Similarly, planting flowers that attract aphid-eating larvae next to plants that are susceptible to greenfly should keep infestations down. Certainly, there is an advantage in mixed planting rather than having beds of a single plant like roses.


It is possible to control some pests, particularly caterpillars, by picking the grubs off the leaves and flowers when you find them. Likewise, slugs can be collected as they appear in the evening and dispatched in a jar of salt water, and the tips of plants covered in blackfly can be nipped off and destroyed. You can also put up barriers, like placing a fine mesh net over the cabbages to prevent the cabbage white butterfly getting in to lay her eggs, and using a finer mesh to keep out fleabeetles, carrot root fly and other flying pests.


One way of helping to control diseases is to remove infected parts of the plant as soon as they are seen. The infected material should be burnt immediately or removed from the garden (probably to the municipal dump, although do not put it into the containers marked ‘greenery for compost’). Similarly, do not put it on your compost heap because the heat generated as the material rots down is not always sufficient to kill the spores of the fungi causing the disease, and so you could simply spread the disease around the garden via your compost. Where plants have shown signs of disease, remove all the old stems and leaves as they die down in the autumn; do not leave them on the ground to overwinter. Although the use of fungicides is not possible for a wildlife garden, there are several safe organic methods available for the control of most diseases.

05. February 2011 by admin
Categories: Pest and Disease Control | Tags: , | Comments Off on Controlling Garden Pests and Diseases


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