Three ways of pest removal
Chemical techniques refer to pesticides which poison the pest. Sometimes they are known under specific names, such as molluscicides, for snails and slugs. Biological techniques are either predators found in the local environment, which are deliberately introduced to attack pests, such as nematodes, which attack eelworms in potatoes. Cultural controls refer to what is done by hand or machine, such as blasting aphids off plants with water jets.
The problem of over-reliance The case of the glasshouse whitefly
It was sprayed heavily, but the sprays left some flies that were resistant to spraying, which bred resistant offspring, causing the chemical sprays to be ineffective, The other controls have their limitations, so the principle is that you need to use all three methods. You do it in a well-thought out, planned way so that techniques are timed well and do not interfere with each other.
First, growers identify the pest. Then they try to eliminate it by cultural methods, but they may also call on the pests' natural predators. This can be done either by importing them from a breeder, or by encouraging wild predators.
For example, if you have a slug problem, frogs, toads and ducks work very well. You might also use chemicals. Select these carefully so that they are not applied when the useful predators are present. So timing is very important. Careful calculation of dosage must be exercised as you do not want excess poison in the soil.
EXamples of controls
Cultural controls can include hoeing and digging. This is particularly important for pests that winter in underground cells, such as sawfly larvae, so this cultural control is timed for winter. Glasshouses clean up in winter, destroying any pests that they find. Grease bands placed round fruit trees prevent the female winter moth from ascending to lay her eggs in winter.
These might include placing nesting boxs in orchards for blue tits, which eat various insect pests, such as codling moths. Encouraging hedgehogs by creating suitable wild habitats for them is an anti-slug technique, as is digging a small frog pond.
Chemicals should be applied sparingly, when necessary and carefully timed and focused on a specific pest. Slug pellets poison the hedgehogs that eat slugs and so are counter-productive, so use organic pellets, which are non-toxic.
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