Effect of Hirschmanniella oryzae infestation on rice Kuriyan K. John, Sheela M. S. College of Agriculture, Vellayani. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract The extent of damage done by H. oryzae on rice plant and its yield was evaluated by a field trial. Rice variety, Jaya was grown with natural population of H. oryzae, five fold increase over natural population, ten fold increase over natural population, natural population and soil treated with carbofuran @ 1 kg/ha, at seven and fifty days after planting. There Was significant reduction of 6.2 to 13.8% in the number of productive tillers; 3.9 to 9.6% in height of shoot; 17.1 to 29.9% in weight of shoot 14.5 to 38.8% in the weight of shoot; 4.0 to 8.0% in the length of panicle 7.9 to 20.5 in the weight of panicle and 7.9 to 22.5% in the weight of grains per plant by the infestation of H. oryzae, over the natural population in soil. The carbofuran treated plants showed an increase of 9.2, 3.3, 14.0, 26.1, 4.92, 1.7 and 16.9% respectively for the above characters. The dry grain weight and straw weigh per plot of 12 sq.m. were also reduced by 12.7 to 45.0% and 11.6 to 28.8% respectively by H. oryzae over the normal population. But the carbofuran treated plants had an increase of 17.9 and 14.6% in dry grain weight and straw weight. When the soil and root population increased significantly in the nematodes inoculated treatments, they were significantly reduced in carbofuran treated plots. Thus the improvement in plant characters with increase in yield in carbofuran treated plants could be attributed to the reduction in soil and root population of H. oryzae and the reduction in plant characters with reduction in yield, due to increase in nematode population. There was a significant negative correlation (−0.93) between nematode population in root and grain yield and (−0.94) between nematode population in the root and number of productive tillers or earheads. Top |