Until the 1990s, orchard and vegetable pests were controlled by regular spraying of broad-spectrum organophosphate insecticides, and acaricides were used for mites. This regime killed most pests and allowed export fruit to meet stringent quarantine requirements. However, the pests started to become resistant, and there was growing awareness that chemical residues were harmful to the environment and human health.
Organophosphates are manufactured from phosphoric acid and are the world’s most widely used insecticides. They were developed in Germany in the Second World War as a by-product of nerve gas, and act by disrupting the central nervous system in insects. They are also dangerous to humans, especially children, who, depending on the degree of exposure, may suffer mild flu-like symptoms or respiratory failure.
Integrated pest management
Many growers now use integrated systems, in which they carefully monitor pests and aim to control them using natural predators. If pesticides are used, they are designed to target certain pests with the least possible harm to the environment or people.
Pheromones are usually produced by female moths to attract males of the same species. Pheromones of several moth species have been isolated and synthesised, and are widely used in traps to check for the presence of pests, or to confuse male moths and disrupt mating.