All India Coordinated Rice Improvement Project, Rajendra Nagar, Hyderabad-500030, India
Studies were conducted on the interrelationships of plant type, micro-climate and brown plant-hopper (BPH) to elucidate information on the nature of insect build up under field conditions. Microclimatic data recorded at 10 cm above water level in the field conditions revealed low temperatures, high relative humidity and low wind velocity when compared with the atmosphere. The situation was aggravated with broad leaved canopy conditions. The wind velocity decreased from atomospheric to plant base level and to ‘still air’ situation in ‘wind break’ plots. Light transmission ratio (LTR) at base level of canopy was found to be the major distinguishing factor among the plant types besides wind velocity. The brown plant-hopper population was invariably high in broad leaved canopy with highest number under ‘wind break’ plot conditions. The spider and mirid bug predator populations was several times lower than the brown plant-hopper population. Yield components were reduced significantly and concomitantly with pest population build up. Apparently narrow leaved canopy favoured lower pest population which reduced the yield losses. Microclimate was codsidered to be an aggravating factor while host sensitivity could be the balancing factor in deciding the BPH build up. There was host-pest interaction which appeared to have determined the yield losses.
