PHENOLOGY OF SORGHUM FLOWERING

Understanding the phenology of flowering, the time when sorghum, Sorgh um bicolor (L.) Moench, is vulnerable to oviposition by the sorghum mi dge, Contarinia sorghicola (Coquillett), would improve the capability of managing this key sorghum insect pest and aid in developing control recommendations. Daily number of flowering spikelets per individual p anicle of 'DeKalb 50', and per panicle in field populations of 'WAC 71 5DR', 'Funk 522DR', and 'DeKalb 59E' sorghum, were calculated from mea surements of centimeters of panicle in bower. The rate of flowering of individual panicles of sorghum increased from Days 1 to 3 and then de clined, with each panicle completing flowering in approximately 8 d. T he most spikelets (1300) per panicle flowered the third day after flow ering began on a panicle. Panicles in a uniformly growing field were f lowering approximately 13 d irrespective of hybrid, with most spikelet s (388 per panicle) flowering the seventh day after flowering began in the field. Almost 48% of the variability in the number of spikelets p er panicle was due to sorghum hybrid and length of panicle. Panicle le ngth and number of spikelets were positively correlated, with 42% of t he variability in the number of spikelets attributable to panicle leng th. Mean panicle length was 26.9 cm. Mean number of spikelets was 2725 per panicle. Accurate assessment of the powering duration of sorghum is critical to understanding the relationship between sorghum midge ab undance and sorghum grain loss.