Harmful soil pests include snails, sciara fly, nematodes and vine weevil. During their life cycle, all these organisms have one or more stages in which they parasitise on the plant roots. In addition to this 'underground' damage they also cause damage to above-ground parts.
On crops in the ground there is a chance that thrips build up a population faster than the leaf miner does. Both insects naturally reach the pupa stage in the top layer of the soil. Other than when growing in the ground, when growing in substrates, a portion of the pupae fall onto the foil covering and dry out.
Nature also provides a solution in the form of natural predators for these soil-related pests. For the above mentioned pests, these are mainly beneficial nematodes and soil mites. The nematodes are real parasites that invade the body of their the host and multiply there. The soil mites can eat larvae of pest organisms and thrips pupae.