440 Bio-efficacy of post-emergence herbicides in transplanted rice Rathod Nilesh Dayaram, Elizabeth K Syriac* and Sheeja K Raj College of Agriculture, (KAU) Vellayani, Thiruvananthapuram, Kerala 695 522 Received: 4 November 2016; Revised: 11 December 2016 Pre-emergence herbicides with high application rates are commonly used for the management of weeds in transplanted rice. However, recent trend in chemical weed management in rice is the use of low dose high efficacy herbicides, which will not only reduce the dose but also make the application easier and economical to the farmer. With this back ground, the present investigation was undertaken to assess the bio efficacy of two new generation post-emergence herbicides, viz. fenoxaprop-p-ethyl and carfentrazone- ethyl in transplanted rice. A field investigation was conducted in farmer’s field in Kanjirathady Padashekaram in Kalliyoor panchayat of Nemom block of Thiruvananthapuram district of Kerala. The soil was sandy clay loam in texture, slightly acidic in reaction, medium in available N and K and high in available P and organic carbon content. The experiment was conducted during third crop season from December 2011 to April 2012 in randomized block design with eight treatments and three replications. The treatments comprised of fenoxaprop-p-ethyl 60 and 90 g/ha, carfentrazone- ethyl 20 and 25 g/ha, fenoxaprop-p-ethyl 60 g/ha + carfentrazone-ethyl 20 g/ha, bispyribac-sodium 30 g/ha, hand weeding twice at 20 and 40 DAT and weedy check. The gross plot size was 20 m 2 (5 x 4 m) and the net plot area was 4.2 x 3.6 m. Medium duration rice variety ‘Uma (MO 16)’ was used as the test crop. Eighteen days old seedlings were transplanted in the main field two to three seedlings per hill with a spacing of 20 x 10 cm. The fertilizer recommendation adopted was 90:45:45 kg N, P and K/ha. The tested herbicides were applied at 20 DAT using knapsack sprayer fitted with flat nozzle. The quantity of spray fluid used for the study was 500 l/ha. Observation on weed density was recorded by placing a quadrate of size 0.5 m x 0.5 m at 40 and 60, and total weed dry weight was recorded by uprooting the weeds in the same area where weed density was recorded at 60 DAT. Weed control efficiency and weed index were worked out by standard procedures. The data on weed density and weed dry weight were transformed using square root transformation. Productive tillers/m 2 was recorded by placing a quadrate of size 0.5 x 0.5 m randomly at two spots in the net plot area and the mean values were worked out. Grain (1000) weight from each plot was also recorded. The grain yield from the net plot area of each treatment was recorded at 14% moisture level and expressed in kg/ha. The data were statistically analyzed using Analysis of Variance technique (ANOVA). Weed flora The major weed flora present in the experimental area were Echinochloa colona (L). Link (jungle rice) among the grasses, Cyperus difformis L. (slender sedge) and Scirpus grossus L.f. (Greater club rush) among the sedges and Limnocharis flava (L.) Buchenau (water cabbage), Ludwigia parviflora Roxb. (water primrose), Ipomoea aquatica Forsk. (water spinach), Lindernia rotundifolia blanc vert (Baby tears), Salvinia molesta D.S.Mitch. (Kariba weed), Marsilia quadrifolia Linn. (Airy pepper wort) and Pistia stratiotes L. Royale (water lettuce) among the broad-leaf weeds. Effect of weed density The weed control treatments significantly influenced the total density of weeds at 40 and 60 DAT (Table 1). At 40 DAT, the lowest weed density was recorded by carfentrazone-ethyl 25 g/ha, which was at par with bispyribac-sodium 30 g/ha and carfentrazone-ethyl 20 g/ha. At 60 DAT, the lowest total density of weeds was recorded by carfentrazone-ethyl 20 g/ha, which was at par with its higher dose 25 g/ha and bispyribac-sodium 30 g/ ha. Among the weed control treatments, the highest total weed dry weight and the lowest weed control efficiency were recorded by fenoxaprop-p-ethyl60 g/ ha. The highest total weed density, weed dry weight and the lowest weed control efficiency recorded in fenoxaprop-p-ethyl 60 and 90 g/ha might be due its lesser efficacy in controlling sedges and broad-leaf weeds, the predominant group of weed flora present in the experimental field. The effectiveness of carfentrazone-ethyl for weed control in transplanted rice was also reported by Glomski and Getsinger 2006). Yadav et al. (2009) reported the effectiveness of bispyribac-sodium against weeds in transplanted *Corresponding author: elizabethsyriac59@gmail.com Indian Journal of Weed Science 48(4): 440–441, 2016 DOI: 10.5958/0974-8164.2016.00112.X Short communication