Temporal variation of insect pest populations of rice and their relationship with meteorological variables in Batalagoda, Sri Lanka

Climate and weather substantially influence on the development and distribution of insects. Forecasting of insect pest outbreaks requires data on insects and climatic information from a thoroughly maintained data base. In Sri Lanka, there are several meteorological stations recording climatic information for over many years; unfortunately, details on the insect pest population are limited. Therefore, the present study was designed to collect information on major insect pest of rice in order to study their population dynamics over the time. A light-trap survey was carried out during 2007-2014 to collect five major pests in paddy fields; Brown Planthopper, Green Leafhopper, White Backed Planthopper, Zig Zag Leafhopper and Paddy Bug to investigate the effect of climatic parameters such as maximum and minimum temperature, rainfall and relative humidity on their population level. The effect of climatic variables on the collected species was evaluated using generalized linear models with a logarithmic link function for poison distribution. Generalized additive model was used to investigate temporal trend of insect population over the time. Maximum temperature showed a significant (P<0.005) positive relationship on the population levels of the whole species studied, while the minimum temperature had a negative influence. Except for Brown Planthoppers and Zig Zag Leafhoppers, population levels of all other species were negatively influenced by the rainfall. Relative humidity had significant negative impact on all insect species. Population variation between years was compared and general trends were observed and models were also developed for the prediction of future pest outbreaks.