Influence of N-Fertilization and Plant Density on Asian Rice Gall Midge Orseolia oryzae (Wood-Mason) and Its Endoparasitoid Platygaster oryzae (Cameron) in Tropical Madurai Region of Tamil Nadu Saran R.1,*, Rani W. Baby2, Kalyanasundaram M.1, Grace T. Myrtle3 1Dept. of Agricultural Entomology, TNAU, AC & RI, Madurai-625104 2Sethu Bhaskara Agricultural College and Research Foundation, Karaikudi-630306 3Dryland Agricultural Research Station, Chettinad-620103 *email: saranagri1989@gmail.com
Online published on 23 December, 2016. Abstract Nitrogen fertilization and plant density hold a strong promise in the integrated management of rice insect pest problem. Therefore, three levels of nitrogen: 100, 150 and 200 kg N ha−1 and three planting densities: 66, 80 and 100 hills/m2 at three different planting dates were evaluated at the college farm, Agricultural College and Research Institute, Madurai for the influence of Asian rice gall midge and its endoparasitoid. The experiment was set up using splitsplit plot arrangement with three replications. Results of the trial showed that nitrogen significantly increased incidence by gall midge (P<0.05) in late transplanted plots which recorded higher damage (10.62% and 12.53% on 15th and 30th October planted crops, respectively). With regard to nitrogen levels, the maximum of 10.51 per cent incidence was observed in plots applied with 200 kg N ha−1 followed by 150 and 100 kg N ha−1 applied plots (10.01% and 9.74%, respectively). Considering the plant densities, increase in plant densities had significantly increased the midge damage. The maximum midge activity of 10.17 per cent was observed in plots with 100 hills/m2. Delayed planting had a significantly increasing effect on the parasitoid activity. The mean parasitization level was the highest (47.66%) in the crop transplanted on 30th October 2015. Increasing nitrogen levels and higher plant density also increased the parasitoid activity recording the highest activity (45.40%) in the plots applied with 200 kg N ha−1 and the maximum parasitization of 45.61 per cent was recorded in plots with 100 hills/m2 which was significantly higher than the other treatments. In all the treatments, mean parasitoid activity increased graduallyfrom 30 DAPto 60 DAP. Conversely, grain yield was significantly reduced with increasing population. Differences among treatment combinations between nitrogen and planting densities however did not produce any significant effect. Top Keywords Asian rice gall midge, N-fertilization, planting density, tropical. Top |