Organic pest and disease control
Ladybird eating aphids
If you are a newcomer to organic gardening you probably think that being organic means lots of hard physical work and simply swapping your conventional sprays for organic ones. You could not be further from the truth. Let Garden Organic introduce you to a few of the basic organic methods used to control pests and diseases in the your garden.
Organic gardening does not mean a lot of extra physical work. It does however require a greater use of your mental faculties. 'Prevention is better than the cure', a saying that is as true for human health as it is for organic gardeners.
So, let's begin with your soil. Healthy growth depends on a healthy soil. Too much fertiliser and your plants will be soft and sappy. The result will be a lovely lunch for the pests and the need for you to spray. Feed your soil with a wholefood diet of garden compost and leafmould rather than using the fast-food artificial fertilisers that are designed to feed only the plant. Feeding the soil rather than the plant will mean stronger growth and better resistance to pests and diseases. Research has already proved this to be true. Looking after the soil is the cornerstone of organic gardening. Healthy plants depend on it. For organic gardeners there is also another very important tool in preventing pests and diseases, this is choosing varieties that have been bred for their pest and disease resistance. For example, blight resistant potatoes such as 'Remarka' and 'Sarpo', and root aphid resistant lettuces such as 'Milan'.
Focusing for a moment on your vegetable garden there is one essential pest and disease control that you must practice: crop rotation. This involves dividing your vegetables into at least four groups that stay together each year but move onto the next part of the rotation every spring. The vegetables are grouped by family as well as similar feeding habits. Apart from being the best way to build soil fertility it is the most important factor in controlling the build up of pests and diseases. All organic growers practice crop rotation.
Protect vegetables with a fine mesh
the Organic Gardening Catalogue)
Cabbage mats available online from
the Organic Gardening Catalogue
Barriers are the best way of reducing pest damage. Simply by covering your vegetables with a fine mesh you will stop them being attacked by flying pests. This works well for carrot rootfly and pea moth. Fine mesh is also an all inclusive way of protecting your cabbages from just about everything. For example: flea beetles, leaf weevils, birds, cabbage white butterflies and white fly.
Other barriers include cabbage collars and bottle cloches. Placing a collar of carpet underlay around the neck of a young cabbage will prevent the cabbage root fly from laying its eggs at the base of the cabbage.
Placing a bottle cloche, a clear plastic drinks bottle with the top and bottom removed, over newly planted vegetables will prevent them being eaten by slugs or anything else that takes a fancy to them. Small gage chickenwire is always useful. Placing it over your newly sown peas can stop them being eaten by mice while they are germinating or being scratched up by cats. Wrap it around your flowering bulbs to prevent squirrels from digging them up.
Netting can be very useful at preventing bird damage to fruit and vegetables. There is also a humming line that can be wound around canes criss-crossed over your vegetables to prevent bird attacks. Netting can also prevent cabbage white butterflies from laying their eggs on your brassicas.
Barrier to prevent
peach leaf curl
Barriers can also be used to prevent diseases. For example, peach leaf curl is a devastating fungus that can simply be prevented by placing a barrier of polythene sheeting over a trained peach tree in the winter. This simple barrier prevents the spores splashing up onto the plant.
Slugs are most people's worst enemy. Barriers of anything sharp and gritty are supposed to protect your tender plants, as is bran (they're supposed to eat it and dehydrate). There are all sorts of products available for slug control on the organic market now. One that springs to mind is a band of copper that gives the slugs electric shocks.
If using a barrier method with slugs remember that success depends on you being extremely generous with the chosen deterrent and not skimping.
Beer traps really do
work against slugs
Codling moth trap
available from the
Organic Gardening catalogue
Another popular method of protecting your plants is to use traps. This can be anything from beer traps for slugs to codling moth traps hung from your apple trees. Sticky traps are very popular with the organic gardener.
A codling moth trap, for example, uses a pheromone placed on a sticky floor. The male moth is attracted to the trap thinking it is a female. On landing he gets stuck in the glue. There are similar traps for plum moths, too.
Greasebands, painted around the trunks of apple trees in autumn are a popular way of preventing the wingless female winter moth from climbing up the tree to mate. Sticky glue is also very useful for glasshouse staging if you have a problem with ants. Sticky yellow bits of card hung up in the glasshouse can help reduce the population of whitefly.
Ladybird eating aphids
Beneficial insects and wildlife are really your best friends when it comes to controlling pests in your garden and vegetable patch. Planting simple annuals amongst your vegetables, such as Californian poppies and marigolds will attract a wealth of beneficial insects like ladybirds and hoverflies who will gobble up your aphids. Plant a few native shrubs and herbaceous perennials (i.e. hazel and hardy geraniums) in your garden; create a pond; leave a small pile of logs in the corner of your garden and feed the birds throughout the winter. Doing any or all of these will keep enough wildlife in your garden to eat thousands of pests and their eggs.
Remember, when trying to control pests and diseases in an organic garden, hygiene is one of the key factors.
If trying to remove a diseased branch from a tree, coral spot for example, cut into healthy wood and always wash your tools in boiling water afterwards.
Always scrub out your pots and give your greenhouse a good scrub every winter to get rid of those over-wintering pests.
Maximising air circulation by correct pruning and leaving just a little more space between your plants can help control fungal diseases, for example powdery mildew in roses.
Finally and most importantly, be vigilant and check your plants regularly so that any pest and diseases don't get a chance to get a hold. For example, if you start checking the centre of your gooseberry bushes in April for sawfly eggs and larvae you can remove them and therefore prevent them from defoliating your crop. Also be wary of accepting onion and cabbage plants from a friendly neighbour, they may well carry the dreadful diseases of onion white rot and clubroot. You will never be able to get rid of these diseases so err on the side of caution. If you have an allotment with either of these diseases then don't even use the same tools or boots in your own garden because you will spread them.
So to all the beginners who thought they were just going to do a straight swap from conventional to organic gardening by simply changing their sprays it is not quite so simple. Organic gardening is the thinking man/woman's horticulture. Planning, forethought, observation and vigilance make for success in the organic garden.
The following factsheets are available online to Garden Organic members: