The general rule in an organic garden is to encourage balance and biodiversity. Refraining from using non- organic pesticides or herbicides, immediately helps the insect population to right itself. Planting companion and attractant plants, and creating helpful habitats such as ponds and wild areas will encourage beneficial predators amazingly quickly.
However if you are taking on a plot that has been previously gardened with pesticides, it may take a while for the balance to re-establish. Whilst that is happening, there are many brilliant organic techniques and tips to help restrict the less helpful members of the garden community.
Slugs and snails are very common garden pests and they can decimate young plants if their population is high.
We have a several pronged approach to working with this problem.
- Hand picking: Children love to go and find snails, do encourage them to take pots with leaves in them around the garden to see if they can find any, (generally under pots, wood, rubble or foliage). Collect the snail/slugs together, and take to local chickens (they love to eat them) or a woodland area to give them a new home, depending on your sensibilities. (It’s not generally a good idea to murder the newly found slugs and snails in front of children, however many seedlings they have eaten!)
Nightly walks around the garden also will show you more slugs, however this may not be so easy or sensible depending on your site. - Slug pubs: a brilliant and effective method of drowning slugs if you can bear it. Sink an old yogurt pot with long horizontal holes cut near the rim, into the ground around vulnerable plants, or mulches. Leave a lip with the holes in it just above ground level, fill with beer (pubs may give you slops for this if you ask), pop a stick into one of the holes to save beetles from drowning, and put the lid on. Slugs are attracted to the beer, and simply go in and drown happy (!). Check regularly, compost contents and refill. It’s amazing how many you can catch this way. Commercial ‘slug pubs’ are also available.
- Barriers: There are many different barrier methods to try, from crushed egg shells, to commercial organic blends, to copper tape around pots etc. All are unpleasant for the slugs as they do not like the sensation of sliding over some of the materials, and copper is said to give them electric shocks. These are more deterrents than 100 % effective I find, and can be very fiddly and impractical over a large area, but useful for small amounts of very vulnerable plants or around bed edges. They need to be maintained and replaced quite often..
- Commercial organic slug pellets: These contain Ferrous phosphate which is non toxic to birds, animals and children, and very effective against slugs and snails. However it is only organically acceptable to use this up to 3 times in a season, and must therefore be targeted appropriately for most vulnerable times eg as seedlings or new transplants, or most loved by slug plant varieties, eg French beans, salads, etc.
Non organic slug pellets are responsible for killing many hedgehogs, birds and other wildlife, as well as being dangerous to children and other animals. Please refrain from using these. - Nematodes: These are available from the Organic gardening catalogue amongst other suppliers and are very effective against the small black slugs that live underground and can burrow into potatoes. Nematodes come in a clay block that simply dissolves and can be watered on the area every 5-6 weeks over the season. They can be pricy if you have a large area, but we use them over just our main crop potatoes and find them extremely effective.
- Slug and snail predators:
Frogs, toads, newts, black beetles, birds and hedgehogs along with many others, make up a formidable slug defence army, eating eggs, juveniles and adults. A pond, will increase your slug patrol no end, and if you are lucky enough to attract a hedgehog to your plot, and no neighbours use non organic slug pellets (which will kill hedgehogs), you have a voracious slug predator indeed. Encourage birds into your garden by feeding them through the winter, and providing nest sites, and provide good wildlife habitat in the form of log piles and mulches, and undisturbed piles of leaves for hedgehog hibernation.
Other common pests
Aphids: Black, white, grey and greenfly can effect plants by sucking out the juices from the leaves, with the resulting tell tale curling effect on the leaves. They can reach high populations quite quickly, and there are various different ways to bring them back into balance.
- Plant beneficial insect attractant plants such as poached egg plant, herbs and marigolds etc around the garden. Simple open pollinated flowers are the best for this. These will attract hoverflies and predatory wasp species that will dine off your pests. Ladybirds and their larva are also voracious aphid eaters, and will be attracted in. Provide habitats for your guests to overwinter in, ladybird houses and lacewing homes can be bought commercially or made simply in the late summer along with leaving an area wild in the winter.
Don’t forget that ants farm aphids for their secretions, and protect them from predators, an amazing relationship really, but remove them from plants when you see this happening if you can so the predators have a chance! - Horticultural soft soap is acceptable, and can be sprayed on overlarge populations if necessary, or just a blast from a hose, or hand squashing can also reduce the population by a good few.
- Pick out the succulent growing tips of broad beans when the first pods are starting to set, as this will deter the blackfly that otherwise would like to come and dine.
- There are also biological controls that are specific to aphid species, so first check out which ones you have, (whitefly in greenhouses is very common,) and release the appropriate control species according to instructions.
- Avoiding spraying pesticides will help enormously as you will not be killing off your helpful species.
Cabbage white caterpillars
Attracting butterflies into the garden is a wonderful thing, but there are one or two species that we would rather deter.
Cabbage white caterpillars can reduce a healthy brassica crop to skeletons within a week or two.
Controls include:
- Barriers: Horticultural membrane/ mesh can be erected to protect your crops, but the holes need to be extremely small, as butterflys can lay eggs through unbelievably small holes given the chance.
- Hand picking: pick off the caterpillars by hand, then feed to birds, remove or squash if you can bear it. This is somewhat effective, but labour intensive.
- The most effective method we have found is an amazing organically approved biological control called Dipel DF.
It can be bought from the organic gardening catalogue and other suppliers, and with regular 2 weekly sprays, keeps your cabbages hole free all through the season without the need for nets or mesh.
Other pests
Cabbage root fly can be kept at bay with horticultural membrane over the crop, or a 2” barrier of membrane around the bed.
Mice can be dissuaded by the addition of some holly leaves among the sowing row as can cats!
There is a mighty stock of clever organic methods and controls to deal with pests that are out of balance. But over time as you increase biodiversity and habitat, you will find that you need less and less outside help as your garden begins to balance and regulate itself.
Diseases
Good hygiene is vital in an organic garden, clearing away and burning diseased plant material, cleaning pots before sowing seeds and noticing problems early and taking action, all help toward the general health of a garden.
Potato and Tomato blight is a disease that affects crops in warm wet summers, and can devastate leaves and then tubers or fruit quickly. It looks like brown splodges affecting the leaves, and spreads quickly. If you notice it on potatoes (generally from June to September, ) cut down haulms (foliage) to the ground and wait a week or two before harvesting the potatoes so the spores don’t spread to the tubers. If they are affected, they can rot in store. Remove and burn the affected foliage as it can spread spores to other plants. With tomatoes, cut off the leaves when seen, and rescue any unaffected tomatoes to ripen indoors.
To avoid this in the first place choose resistant varieties, give generous planting spaces for good ventilation, rotate crops (see below) feed the plants well, and water the soil not the foliage.
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