Population dynamics of major arthropod pests and their natural enemies on okra

Abstract

An investigation was carried out on the population dynamics of major pests and their natural enemies on okra during kharif, 2016 and 2017. Results revealed that during both seasons, whitefly (Bemisia tabaci) and leafhopper-Amrasaca (Sundapteryx) biguttula occurred from the last week of July (30th Standard Meteorological Week) whereas, fruit borer (Earias vitella) and red spider mite (Tetranychus cinnabarinus) appeared in 34th and 37th SMW during 2016 and 2017, respectively. Peak population of B. tabaci (29.00/15 leaves) and A.biguttula (179.25/15 leaves) was observed in 32nd and 37th SMW, respectively. The peak infestation of E. vitella (52.43%) and T. cinnabarinus (247.25/sq.cm/15 leaves) was observed in 34th SMW and 40th SMW, respectively. Incidence of B. tabaci showed significant negative (r=-0.786) correlation with maximum temperature and with minimum temperature (r= 0.904) and evening humidity (r= 0.766) showed significant positive correlation; T. cinnabarinus showed significant negative correlation (r=-0.964) with minimum temperature; and E. vitella having significant positive (r= 0.867) correlation with maximum temperature, while minimum temperature(r=-0.800) and evening relative humidity (r=-0.960) had significantly negative correlation. Among the natural enemies viz., coccinellids (r = 0.911), spiders (r = 0.918), rove beetles (r= 0.895), Geocoris bug (r= 0.672) and carabid beetles (r= 0.701) had significant positive correlation with A. biguttula, whereas, coccinellids (r =-0.991) and Geocoris bug (r =-0.984) had significantly negative correlation with T. cinnabarinus.