Temporal distribution of rice sheath mite <i>Steneotarsonemus spinki</i> Smiley (Acari: Tarsonemidae) as influenced by the climatic parameters in the low-country wet zone of Sri Lanka

Abstract

The rice sheath mite (RSM; Steneotarsonemus spinki Smiley) is considered as the most destructive mite pest of rice (Oryza sativa L) in most of the rice-growing countries including Sri Lanka. Under heavy infestation of RSM, yield losses could reach up to 95%. Intermittent heavy showers negatively affects the RSM population while prolong dry periods influence positively on its population growth. However, no detailed studies have been done in Sri Lanka to elucidate the influence of weather conditions on population dynamics. This study was conducted in three different locations in the low country wet zone (LCWZ; elevation < 300m amsl; annual rainfall > 2,200mm) from 2013-2015 to examine the relationship between selected weather parameters and population dynamics of RSM. An experiment was laid out in a randomized complete block design in three replicates where crop was planted in 15-day intervals under pesticidefree condition. In weekly intervals, 25 leaf sheaths from 10 randomly selected plants from each plot were observed under microscope to count the number of mites. Climatic data were collected from respective meteorological units for the study period. The results revealed that, rainfall (r=-0.543) during the 2013/2014 Maha season at Bombuwala and RH (r=-0.86) during the 2013 Yala season at Labuduwa have a negative correlation with the RSM population, while temperature between 29-32 °C (r=0.794 and 0.902 at Bombuwala and Labuduwa, respectively, during the 2013 Yala season) and more sunshine hours with dry weather conditions affected favourably. Abundance of RSM-infested host plants in the previous season had a significant influence on its occurrence in new rice crop under favourable environment conditions.