Management of major insect pests of rice through organic manures with special emphasis on use of neem and karanj cakes

Abstract

The field experiment conducted at Birsa Agricultural University farm during 2010 and 2011 revealed that silver shoots (SS), caused by Orseolia oryzae (gall midge) was minimum (1.05, 1.26 and 1.21, 1.96%, respectively) in plots treated with neem and karnaje cake @ 2.5 t ha-1 against the highest with plants treated with the sole use of N @ 100 kg ha-1 through urea (20.15 and 24.45%) during 2010 and 2011, respectively. The neem cake application also recorded minimum incidence of Scirpohaga incertulas Wlk. (YSB) (1.92 and 2.65%DH) and was at par with karange cake (2.75 and 3.88% DH) but significantly lower than that of sole use of nitrogen @ 100 kg ha-1 through urea (28.34 and 31.75% DH) and full dose (100%) of recommended chemical fertilizers N,P,K @ 80:40:40 kg ha-1 (19.89 and 22.63% DH) during 2010 and 2011, respectively. However, full dose of RDF remained significantly superior over sole use of N @ 100 kg ha-1 (in the form of urea) in suppressing the incidence of gall midge and YSB during both the years of experimentation. Full dose of green manure (GM) applied through dhaincha, Sesbania rostrata L. (@ 10 t ha-1) supplemented with 50 per cent RDF (N,P,K @ 40:20:10 kg ha-1) was also found significantly effective than that of RDF (100%) of in reducing the pest incidence. Almost similar trends were found in case of incidence of Nephotettix spp. (GLH), Cnaphalocrosis medinalis Gn. (leaf folder) and rice hispa, Dicladispa armigera Ol. As regards the yield of paddy grains (41.37 and 43.80 q ha-1) the maximum was recorded with 100 per cent RDF followed by GM @ 10 t ha-1 50 per cent RDF (37.63 and 40.68 q ha-1) during the respective years. Among the organic treatments, cake (NC) application proved little superior (33.00 and 36.88 q ha-1) but almost at par with karanj cake (32.33 and 35.68 q ha-1) in realizing yields of paddy grains during 2010 and 2011, respectively. It was noticed that fertilizer nutrients supplied through organic sources showed remarkable reduction in the prevailing major insect pest’s infestation levels and in turn produced higher yields ie, 25.38 and 28.50 q ha-1 with FYM, 32.33 and 35.68 q ha-1 with KC and 32.00 and 36.88 q ha 1 with neem cake against the significantly lower yields of 20.14 and 24.68 q ha-1 with N through urea @ 100 kg ha-1 and lowest 9.75 and 14.68 q ha-1 from untreated control (No, Po, Ko) during 2010 and 2011, respectively. The findings suggests that balanced dose of N,P,K is effective both in terms of suppression of pest incidence and realization of higher grain yield. Moreover, neem cake and karange cake that contains considerable amount of azadirachtin and karanjin, respectively proved their superiorty and higher effectiveness in pest reduction and yield enhancement in the organic mode of rice production.