1.6 Non-chemical plant protection methods

For thousands of years plants have been cultivated without the use of chemical pesticides. Today many attempts are being made to find alternatives to pesticides in order to have environmentally safe plant protection.

Biological control of pests involve the use of living organisms, including virus and natural enemies. This includes the use of predators, parasitoids (organisms with a parasitic mode of life and which ultimately kill their hosts), pathogenes (organisms which cause communicable diseases) and antagonists (organisms which can defeat pests or keep them at a low level). The organisms used for biological control are first and foremost insects, mites, nematode, fungi, bacteria and virus; in other words the same categories of organisms one usually attempts to control. Using insect pheromones to catch large numbers or to confuse pest behaviour is also an aspect of biological control methods.

Integrated pest management - IPM. In addition to using other organisms and natural hosts, integrated pest management also involves other methods to hinder pests, for example using cultivated plants which are not affected or only slightly affected by harmful organisms. The aim is to control pests and diseases, not to exterminate them. Several methods can be combined, such as the use of pesticides, mechanical measures, manual methods etc. When using chemicals in such programmes, the pesticide must be carefully selected (with regard to selectivity, effect on natural enemies etc.), and used in as small quantities as possible. An important aspect is the prospective financial loss: How extensive must the pest attack be for the use of pesticide to be economically justifiable? If the attack is not very widespread, the pesticide treatment will cost more than the estimated profit from the crop. By IPM the different methods can interact and give a better total result than if only one agent was being used.

Resistance: Different cultivated plant species have different tolerance levels of pests and plant diseases. Systematic plant breeding has given crops which are resistant to diseases or pests. Some species of wheat, for example, have become resistant to black stem rust and other fungal diseases. Some species of rice have been bred to become resistant to pest insects and virus, and to the fungus Pyricularia oryzae. For the farmer, resistance is a simple and inexpensive plant protection method. Seed manufacturers collect information about the resistance of different seeds. The International Agricultural Research Centres, with support from the Consultative Group on International Agriculture (CGIAR) have focused on resistance when breeding species for tropical and subtropical climates.

Non-infectious plant material: Insects, mites, nematode, fungi, bacteria and virus can accompany seeds, seed potatoes, scions, cuttings and other propagation material. Setting up a control agency to ensure that seeds and all propagation materials are noninfectious is therefore of great importance. It is especially important when importing seeds from other countries and parts of the world (see booklet No.1 "Agriculture").

Quarantine: Most countries have compiled lists of pests, virus, bacteria and fungi which do not exist in their country. Importing countries should always obtain documented proof that the seed imported is non-infectious. Other measures to avoid importing pests are inspection on arrival and growing in quarantine. Inspection routines and growing in quarantine are generally poor in developing countries. Banning all import of seeds from certain cultivated plants can be a possible measure, but such a ban requires strict control. There are numerous examples of pests spreading rapidly from one country to another soon after having entered the continent. A rust fungus on maize was imported to West-Africa in 1949, and in the course of just five years it had spread to all parts of the continent as well as to Madagascar. Another example is coffee rust, which is of African origin. When discovered in Brazil in 1970, measures were taken to exterminate it. The attempts were unsuccessful, and there is now coffee rust in all coffee producing countries in South and Central America.

Regional plant protection organisations: To avoid the spreading of pests, regional organisations have been established to coordinate lists of hazardous pests, quarantine regulations and other measures against spreading. Some such organisations are the FAO Caribbean Plant Protection Commission, the European Plant Protection Organisation, the Inter-African Phytosanitary Commission, the FAO Near East Plant Protection Commission, and the FAO Plant Protection Committee for Southeast Asia and Pacific Region.