1Department of Entomology, Directorate of Rice Research, Rajendranagar, Hyderabad-500030, Andhra Pradesh, India.
Department of Entomology, Acharya N.G. Ranga Agricultural University, Rajendranagar, Hyderabad-500030, Andhra Pradesh, India.
Monitoring studies were carried out at Medchal during Khorifl 996 to Rabi 1997 on rice yellow stem borer (YSB), ScirpophagQ incertulas using natural blend (3:1) of (Z)-l 1-hexadecenal and (2)-9-hexadecenal. Three peak periods of moth activity during July, August and September in Kharif and two during January and March/April in Rabi were noticed. Late planted crop was affected more than early planted crop. It is evident from the temporal relationship between peak periods of pheromone trap catches and field infestation that peak dead heart and white ear infestation occurs 2 and 3 weeks after peak/sudden increase in moth captures, respectively.
From the regression equation worked out with trap catch and field infestation data, the trap capture of 30 and 19 male moths/week/trap seemed to result in 10 per cent dead heart and 5 per cent white ears, respectively. When catches exceed 30 male moths per trap/week and about 95 to 110°C accumulate from such time (degree days accumulated up to hatching), timing insecticidal application is considered as effective and economical, as the time synchronizes with the occurrence of first instar larvae.
Both larval development and adult emergence of YSB are affected at temperatures below 16°C and above 35°C. Maximum temperatures of 29–30°C and minimum of 20°C are the most favorable for the YSB development. Under these conditions, development from egg to adult is completed in 430 to 530°C degree days (DD), while under adverse conditions (below 16 or above 35°C) 630 to 670°C DD would be required to complete the development.
