Some are resistant to pests, e.g. onions, beetroots, carrot, spinach and lettuce. Some are not, such as tomatoes, rape, covo, cabbage, etc. Therefore, you should plant the different crops so that they complement, feed or protect each other. Make sure that your plants are properly spaced vertically and horizontally, and that they are companions, repellents or attractants. This means that some plants will be enriching the soil by fixing nitrogen to the ground, e.g. leguminous plants, while some give a smell that repels harmful insects or attract some insects that are useful to our crops.
Most herbs have such qualities, e.g. mint, fennel and rosemary, and flowers like marigold.
By changing the places of crops from season to season you discourage the development of colonies of pests that feed on a particular crop. Rotation is particularly useful with crops which are affected by pests that are resistant to most chemical poisons - a good example is the red spider mite that affects tomatoes. There are plants that can be used instead of chemical poisons to prepare repellent sprays. The smell of these plants is an effective repellent to a number of common pests, such as scabs in apples, cucumber and nematodes in tomatoes. The ground chilis are left to soak overnight in water.