Agriculture - Initial Environmental Assessment Series No. 1 (NORAD, 1995): Part I: General account: 3. Possible environ mental impacts: 3.6 The spreading of pests and diseases

Agriculture - Initial Environmental Assessment Series No. 1 (NORAD, 1995)

Part I: General account

3. Possible environ mental impacts

		(introduction...)
		3.1 Introduction
		3.2 Impacts on air and climate
		3.3 Impacts on soil
		3.4 Impacts on wafer resources
		3.5 Impacts on ecosystems, natural and cultural landscapes, and historical relics
		3.6 The spreading of pests and diseases
		3.7 Impacts of the use of seeds and biotechnology
		3.8 Changes in land use and impacts on traditional ways of life and the utilization of natural resources
		3.9 Impacts on other existing or planned activities

3.6 The spreading of pests and diseases

The choice of farming systems and plants for cultivation can have consequences for the development of pests, diseases, and weeds. The introduction of new plants and varieties, changes of the cultivation system through e.g. a transition from intercropping to monoculture, or through the partial or full abandoning of fallowing, may cause certain pests to thrive. In the growing of durum and maize, one experienced that the weed Striga may spread when the cultivation becomes more intensive. No chemical remedy exists to date against this parasitic weed which attacks the roots of the useful plant. Cotton is an example of a choice of crop which may result in the thriving of pests in that the plants attract these and function as a propagation site for pests that attack other cultivated plants,

The one-sided emphasis on chemical control of pests and diseases has been met with growing scepticism despite the development of new agents with less serious consequences for environment and health. So-called integrated methods of pest control (Integrated Pest Management - IPM) are used to an ever increasing extent. These combine different methods, such as e.g. the use of resistant varieties of cereal, non-infectious seed corn, rotational cropping, intercropping, fallowing, biological pest control, and restrictive, if any, use of chemical agents (e.g. spot spraying). Integrated methods are more environmentally friendly than are chemical ones, and they should be prioritized where possible. (See booklet 13 "Plant protection").

Several tropical diseases are carried by water and may be disseminated through irrigation systems and flood control constructions (cf. booklet 7 "Water supply"). Local or central health authorities should take part in the planning of such projects, in order to clarify any risk of the project bringing new diseases into the area or of aggravating existing problems. The health authorities should also be able to offer an assessment of the possibilities to master new or increased problems through preventative or curative health measures.