Incidence and Severity of Rice Diseases and Insect Pests in Relation to Climate Change

Abstract

Climatic factors especially temperature and relative humidity are the key factors influencing development of any insect pest and disease of rice. CO2 is the key factor for global climate change, resulting increase in temperature. The intergovernmental panel on climate change predicted that with the current emission scenario, global mean temperature would rise between 0.9°C and 3.5°C by the year 2100. Under such condition frequency of precipitation, intensity of drought and UV-B radiation is predicted to increase, which might affect the structure of rice plant and intensity of insect pests and diseases. Climate change may change the pest–plant relationship resulting in positive or negative impact on incidence and severity of different diseases and insect pests. Sheath blight (Rhizoctonia solani), a minor disease in early 1970s, is now a most destructive disease of rice. Similar change has also been observed on the incidence and severity of some other diseases and insect pests. Ear-cutting caterpillar (Mythimna separata), a major pest of rice in Bangladesh in 1960s had only a few occurrences in the last few decades. Besides, leaf roller (Cnaphalocrocis medinalis, Marasmia exigua) that had lower ranks in the list of major pests has been coming at the top of the list since 1980s. In Bangladesh many interventions such as change in crop diversity, variety, cropping intensity, irrigation, fertilization, etc. along with climate change in the rice production system affected incidence and severity of insect pests and diseases. However, exact and individual contribution of such factors or interventions has not been worked out in Bangladesh or elsewhere. Probable change in the years to come on the status of insect pests, pathogens and natural enemies along with change in the host plants due to global climate change is discussed in this paper.