Impact of fertilizers and irrigation interval as well as methods on incidence of aphid and whitefly in Bt cotton

Abstract

Field experiment was conducted to study the impact of fertilizers and irrigation on incidence of aphid and whitefly in Bt cotton at Instructional Farm, College of Agriculture, Junagadh Agricultural University, Junagadh during Kharif, 2018. In case of nitrogenous fertilizer, lowest aphid index and whitefly population was recorded in nitrogen level N1 (180 kg /ha). Whereas, in case of phosphorus fertilizer, lowest aphid index and whitefly population was recorded in phosphorus level P3 (75 kg P205 /ha). Moreover, Lowest mean aphid index and mean whitefly population was recorded in the treatment combination of N1P3 [180 kg N/ha + 75 kg P2O5/ha] and N1P2 [180 kg N/ha + 50 kg P2O5/ha], respectively. In case of irrigation intervals and methods, for aphid population, I3 (21 days irrigation interval) and M2 (Ridge and Furrow) registered significantly lowest aphid index. While, best treatment combination was I1M2­ [7 days interval + Ridge and Furrow] that found lowest aphid population. For whitefly, I3 (21 days irrigation interval) and M2 (Ridge and furrow) recorded lowest whitefly population. Moreover, best treatment combination was I3M2 (21 days + Ridge and furrow) and found lowest whitefly population. The highest cotton yield found in plots of N3P2 [300 kg N/ha + 50 kg P2O5/ha]. The aphid and whitefly incidence declined with decreased nitrogenous fertilizer level as well as increased phosphorus fertilizer level.