The Need for Integrated Pest Management (ipm)

Much attention has been given to the use of chemical insecticides since the development of DDT which proved important for controlling mosquitoes and many other insect pests until Rachel Carson in her book "Silent Spring" pointed out its adverse impact on birds. More recently greater concern has been expressed about other chemical insecticides having a detrimental impact on the natural enemies of pests, bees and moving into rivers and other areas. The EU has now promoted Integrated Pest Management as an alternative system to reduce the use of chemical pesticides. IPM is not a new idea. In the USA, IPM was first mentioned around 1959 when in California, it was proposed that insecticides should only be applied if the number of pests exceeded an economic threshold, thus encouraging scouting to assess the number of pests in a crop. Earlier, in Central and Southern Africa when it was decided to grow cotton, seed of a variety "Cokers Wild" was imported from USA but suffered severe damage caused by jassids. Luckily in South Africa seed had also been obtained from India and soon a variety with hairs on leaves was introduced that survived jassid damage, although bollworms still restricted the yields. Then in 1938, it was decided that there had to be a closed season of two months in which no cotton plants should be present. This action was to reduce bollworms entering a crop as soon as fields were sown with cotton when the rain season began in November. Bollworms, Diparopsis castanea, the red bollworm and Helicoverpa armigera, the 'American bollworm' still caused damage, so when trials began with endrin and then DDT in 1958, it was pointed out that it was important to gain more conjunction with other forms of control. While studies using insecticides continued there were other investigations to determine the possible use of traps with pheromone to reduce bollworm damage. The immediate work was to collaborate with extension staff to train farmers how to scout for bollworm eggs and spray the insecticide recommended for the bollworms detected in the crop.