Influence of the Green Revolution on the Insect Pests of Rice: With Particular Reference to Bangladesh

The intensified rice cropping of the green revolution boosted the year-round availability of resources for rice pests in Bangladesh. The profuse tillering ability of the semi-dwarf plant type markedly increased the available food supply and volume of suitable micro-habitats for pests. At the same time, a small number of high-yielding varieties replaced hundreds of traditional cultivars, dramatically reducing the rice genetic diversity – with profound consequences for pest abundance. The new cropping system also increased the use of chemical fertilisers and pesticides, the latter affecting the natural balance between pests and their natural enemies. Excessive use of nitrogenous fertilizer enriches the plant nutrients, which then encourages the build up of certain pests. The extension of irrigated rice cropping over more than 4 million ha changed the typical characteristics of the dry season providing a humid microclimate suitable for many pests. This paper draws on data from weekly surveys of rice plots at the BRRI experiment farm, Gazipur, based on the field counts, insect numbers, removal of rice plants for examination and the dissection of stems; and also on farmers' field surveys carried out regularly by BRRI entomologists since early 1970s. Pest outbreaks reported by mass media as well as by the Department of Plant Protection were also considered. Critical changes in the pest status brought about by the green revolution are discussed by dividing the pest complex into those pests that were encouraged or elevated, and those pests that were retarded or reduced by the new agro-ecological conditions.