Introduction

Most of the pesticides covered in this chapter are toxic to many organisms, and most show little or no selectivity at the biochemical level. Some are used to eradicate all weeds, pests and diseases from soil. Others are used to control mammalian pests including rats (such as Rattus norvegicus – the brown rat), house mice (Mus musculus), rabbits (Oryctolagus cuniculus) and moles (Talpa europaea). Selectivity of action is only achieved through careful placement and/or use such that these compounds do not come into contact with non-target species, and particularly people working with them. The extent to which this is achieved varies: serious illness and death have followed careless use of some of these compounds.

Soil sterilants and fumigants are often classified as general biocides rather than pesticides and kill a wide range of organisms, as do some vertebrate poisons. Other vertebrate poisons such as rodenticides may be more selective in their action, but not to warm-blooded animals, and are thus toxic at low doses to mammals and birds. However, effective antidotes to these compounds are available, reducing the risk to the health of human beings. One of the major problems with some rodenticides in the UK is their use in illegal poisoning of game birds, some of which are rare species.

Soil sterilants

Sterilisation of soil to remove unwanted weed seeds as well as soil-borne pests and diseases is commonly carried out with high value crops. However, it is an expensive operation, and has been superseded in some situations by other growing techniques.