Common Garden Pests and How to Deal with Them
Slugs and snails
These are probably at the top of every gardener’s hit list. Slugs live in soil and snails in brickwork, so depending on your garden you may be unlucky and have both. There are almost as many solutions as there are gardeners, so test a few and see which works best for you. Putting them in salt water or offering them beer (in which they drown) are popular solutions but you are left with a horrible mass of squishy corpses.
Organic slug pellets made from ferric phosphate are reasonably successful and the nematode Phasmarhabditis hermaphrodite works well but both need to be regularly re-applied. A good method, especially in a small garden, is to provide protection for vulnerable or young plants. Sharp mulch or gravel will create a slug- and snail-proof barrier. Salt, soot, eggshells and orange peel will do the same, but look as unattractive as a chewed plant. Sequestered seaweed will feed the soil and deter them.
Copper tape can be put around pots. These barriers need to be about 2.5 cm/1 in wide and will last until the soil is disturbed. With all of them it is vital that no leaves overhang and act as edible bridges. The most vulnerable plants are clematis; lupins, hostas, delphiniums, marigolds, stocks, tobacco plants, tulips, almost anything when it is young, and many vegetables. Spiky or hairy plants, those with leathery leaves and most herbs are safe.
Aphids
Aphids suck the sap of plants and can distort growth and increase the risk of disease and mould. They include green, brown and black fly. Roses, honeysuckle, nasturtiums, potatoes, carrots and lettuce are at most risk. Birds, lacewings and ladybirds will all help but they are unlikely to be able to solve the problem for you as aphids breed so fast. In a small garden, you can remove aphids by hand. A strong jet of water will dislodge them, as will a weak soap solution, but these methods cannot be used on young plants. A weak solution of seaweed spray will get rid of the aphids and benefit the plant. Garlic will act as a deterrent if grown alongside vulnerable plants. Simply push a clove into the ground and let it grow up. The leaves are unobtrusive and the smell of the garlic will not be transferred to the other plants. Nematodes can also be used.
Ants
These can weaken roots with their nests and they also ‘farm’ aphids as they eat the honeydew that aphids excrete. The best way to destroy the nests is to pour boiling water into them.
Caterpillars
Caterpillars eat leaves and flowers but they provide valuable food for birds and do eventually turn into beautiful butterflies. Nematodes are available, but remember that you will be killing the butterfly that would emerge from the catepillar. An alternative, if slightly antisocial solution is to throw the caterpillars into your neighbour’s garden and hope that they come back as butterflies! Basil, borage, hyssop, rosemary, sage and thyme will deter the cabbage white caterpillar.
Vine weevils
These cause particular problems in containers. The adults eat leaves and lay their eggs in the soil and the grubs then eat the plant’s roots. Vines, camellias and heucheras are also at risk. Between spring and autumn the adults can be killed by applying nematodes (Heterorhabditis megadis or Steinemana carpocapsoe) or you can put barrier glue around the container.
Shield bugs
These eat a variety of soft fruits and vegetables and increase the risk of disease on all plants. The brown type is relatively harmless but the bright green ones can do great harm. They are easy to spot and can be picked off and killed.
Red lily beetle
This is a conspicuous bright red beetle that does great damage to lilies. Pick off and kill any you see.
Moles
Moles can ruin lawns but spurge or rue planted around the edge will deter them. There are innumerable other deterrents ranging from the smell of garlic or moth balls to the sound of a radio or the vibration of a toy windmill or flag. Any of these should be placed at the entrance to the tunnel and will drive the mole away. Traps are available but seem unnecessarily cruel for such appealing animals.
Rabbits
Rabbits can be a big problem as they will eat all young plants and many older ones. You can put wire collars around young plants or fence off the whole area but the netting needs to be 1 m/3 ft tall with at least one quarter below ground. Alternatively, get a dog!
As our climate changes, many pests are spreading to new areas. If you encounter something you do not recognize, take a sample to be identified so you can deal with it. Remember that not all creatures that appear in the garden are a nuisance. It is well known that ladybirds eat aphids, but so do hoverflies and lacewings. Although birds are pests regarding fruit, they have their uses as many eat slugs and snails. Frogs, toads and shrews are also invaluable helpers, as are hedgehogs.
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