Bodrun Nessa
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Moin U. Salam
Department of Agriculture and Food Western Australia (DAFWA), South Perth, WA6151, Australia.
A.H.M. Mahfuzul Haque
Department of Plant Pathology and Seed Science, Sylhet Agricultural University, Sylhet-3100, Bangladesh.
Jiban K. Biswas
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
M. Abdul Latif
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
M. Ansar Ali
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Tahmid H. Ansari
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Montasir Ahmed
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Nargis Parvin
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
M. Zakaria Ibne Baki
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Subrima Islam
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
M. Sirajul Islam
Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh.
Jean Galloway
Department of Agriculture and Food Western Australia (DAFWA), South Perth, WA6151, Australia.
False smut, Flowering time, Ratoon, Rice, Sunshine hours, Transplanting time,
Bangladesh Rice Research Institute Gazipur, Bangladesh
Pest Management
The experiments were conducted in the research farm of the Bangladesh Rice Research Institute (23°59´ N, 90°24´ E), Gazipur, Bangladesh during T. Aman season of 2014 and 2015. This farm has built up an intensive rice - ecosystem over the last 40 years while growing rice in as many as three seasons annually in about 88 fields spread over 35 hectare area. It is situated at about 35 m above the mean sea level and has a subtropical climate strongly influenced by the south - western monsoon.Effect of the varying flowering times on natural incidence of RFSm was investigated in repeated experiments laid out following a randomized complete block (RCB) design with 10 replications in 2014 and three replications in 2015. To generate wide rang e of flowering time, seven different transplanting times (15 June, 30 June, 15 July, 30 July, 14 August, 29 August and 13 September) of BRRI dhan49 (a highly susceptible variety) served as treatments in 2014 trial. However, 12 different transplanting time s (19 May, 4 June, 19 June, 4 July, 20 July, 4 August, 19 August, 5 September, 19 September, 5 October, 19 October an 5 November) of the same variety were used in the 2015 trial. The individual plot was 2.5 m × 2.5 m in 2014, and 30.5 m × 2.5 m in 2015. Thirty-day-old seedlings were hand transplanted at two or three seedlings per hill, maintaining a spacing of 20 cm × 20 cm. The crops were fertilized with recommended doses of nitrogen (N) (200 kg ha-1 as urea), phosphorus (P) (63 kg ha-1 as triple super phosphate), potassium (K) (84 kg ha-1 as muriate of potash) and sulphur (S) (56 kg ha-1 as gypsum). Nitrogen was top dressed in three equal splits: 20, 35 and 50 days after transplanting (DAT), whereas P, K, and S were applied once, during final land preparation. The crops received moisture predominantly through monsoonal rains, but supplemented by irrigation water to maintain a water level of 2 to 3 cm. Management of the crops included manual weed control twice, at 30 and 45 DAT. No insecticide, fungicide or other chemical were used for pest and disease control. No artificial inoculation was conducted to modify natural disease pressure.
For cartooning, the hills in the main crops were harvested at maturity by manually cutting the tillers at 40 - 60 cm height. No additional crop management practice was applied for ratoon. In the 2014 trial, ratoon voluntarily generated in two plots transplanted on 15 June, and nine plots transplant ed on 15 July. However, in 2015 trial, rattoon generated in all the plots transplanted on 19 May and 19 June. Dates of 50% flowering were recorded for each transplanting time on main crops and ratoon. In addition, the progression of newly formed smut balls on ratoon was recorded by at three days interval during 15 August 2015 to 15 January 2016. The trials were assessed for disease incidence by counting smut ball(s) bearing panicles (diseased panicles) and total panicles in each plot at the late ripening stage. The same was done for ratoon. The disease incidence (DI) on main crops and ratoon was calculated using the following equation DI = [ (Number of diseased panicles)/ (total number of panicles)] × 100 Eq. (1) All the DI values were summarized against 50% flowering time of main crops and the ratoon. The DI data were analyzed and compared at the 95% confidence interval (CI) using an in - built formula in MS Excel 2010. Data on five weather parameters, maximum temperature (°C), minimum temperature (°C), relative humidity (%), sunshine hours and rain - days (number), were summarized for 5 - days prior to 15 days of each record of 50% flowering to find any association of weather to the level of disease incidence. The daily weather data for 2014 and 2015 gathered from the Physiology Division of BRRI were used for this purpose. In order to relate DI with weather parameters, the range of DI in both years was categorized into three sections of flowering window: “early” ( 5 August to 12 October) , “mid” ( 17 October to 23 November ) and “late” ( 4 December to 28 December ). The association of five weather parameters to DI in the three defined periods of flowering window was measured through correlation. The significant weather parameters from correlation study were subjected to regression analysis relating DI.
Bangladesh Rice j., 19(2): 28-34, 2015, ISSN: 1025-7330
Journal