Effect of temperature on larval emergence from Heterodera avenae cysts Bhatti D. S., Malhan Indra Department of Nematology, Haryana Agricultural University, Hissar. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract Effect of constant temperatures, i.e., 10, 15, 20, 30 and 40°C on larval emergence from old and new cysts of Heterodera avenae and of fluctuating room temperature, from only old cysts, was studied during 1973–1975. The contents of field - collected cysts were recorded during April, 1973 to November, 1974, In all, there were 100 cysts in four replicates at each temperature. The object of this study was to determine optimum temperature for larval emergence in observations revealed that differences in larval emergence from old cysts at 10°C, 15°C and 20°C were significant. As is evident from total hatch, the optimum temperature might be around 20°C. However, at fluctuating room temperature, the maximum larval emergence took place at 18°C, this observation points to the possible existence of optimum temperature between 15°C and 20°C. For larval emergence from new cysts, there was significant increase at 15°C as compared to 10°C, a significant decline at 20°C and little emergence at higher temperatures. This indicated that for larval emergence from new cysts the optimum temperature might be between 10°C and 15°C. Thus there appeared to be different temperature optima for larval emergence from old and new cysts of H. avenae. The difference in temperature optima of cysts of varying ages may provide an explanation for variance between cyst numbers per unit of soil and the larvae emerging in field, causing varying pathogenic effects on host crops. Further, the total emergence of larvae during one season might be governed by the proportions of new and old cysts in which they are present in infested fields. The observations on contents of the field-collected cysts did not show much greater variation except a slight decline during winter months. Top |