Green pest control is an aspect of integrated pest management, the process of combining chemical, cultural and biological controls to attack pests. In green pest control the chemical element is played down at the expense of other elements, though some chemical substances are permitted.
The first element of green pest control is cultural practices. These are the gardening techniques that kill pests. Prime among them is good hygiene. This means not leaving plant litter or debris lying around where pests can hide during the day. In greenhouses it means clearing out containers and disinfecting them to prevent pests such as vine weevils hibernating in winter. Cultural controls might also involve spraying fruit trees with jets of water to destroy aphids. This is important at the times when aphids [greenfly] are present on plants.
Cultivation of soil is important. If you dig the soil in winter certain pests that hibernate in cells in the ground will be exposed. They will then be liable to be eaten by predatory birds. Rolling lawns is a useful defence against vine weevil larvae, which eat the roots of plant, as the roller will crush them.Grease bands can be placed around fruit trees in winter to prevent winter moths from climbing into them to lay eggs. The female moth cannot fly.
Slugs and snails can be attacked by means of a variety of methods. Beer traps are useful. These are jars half filled with beer. Slugs love the smell and crawl into them and drown. Snails are also vulnerable to salt on paths, as salt dries them up. They dislike soil in which soot has been included, and they are said to dislike egg shell strewn around plants, though this does not always work.
Biological controls involve setting predators on the pests. These can be wild animals that eat the pests. Many gardeners place nesting boxes for blue tits on the trees, as the tits eat various pests. You can also encourage hedgehogs, which eat slugs and snails. Ducks also are great consumers of these pests, so they can be kept in the garden.
Nenatodes are minute invertebrates that dwell in soil. You can purchase them from dealers and apply them by the watering can dilute in water. They burrow into the nervous system of slugs to paralyse them and render them vulnerable to predators as they lie motionless.Nematodes need renewing every few weeks.
There are also specially bred predatory insects for greenhouses. You have to purchase the predator for the pest. Aphids can be combatted by the tiny predatory wasp Aphidoletes aphidmyza. There are other pest predators depending upon which pest you are which pest is troubling you.
Some chemicals are permitted. The soil association permits organic growers to spray fruit trees with soft soap, which gums up their respiratory systems. There are also organic slug pellets. Non-organic pellets are monstrous, as they poison not only the slugs but the hedeghogs and birds that eat them. Hedgehogs die in agony if they eat slugs that have consumed these pellets. Organic pellets do not poison the slug but swell inside it and gum up its bowels.
All techniques are useful, but it is important to avoid certain chemicals which are thought to be environmentally harmful. Any organo-phosphates should be avoided, as they are a threat to useful wildlife. Neonicotinoides have been implicated in threats to bees. Organic growers cannot use these complex chemicals.