EVALUATION OF SURVEY METHODS FOR ESTIMATING SORGHUM MIDGE (DIPTERA: CECIDOMYIIDAE) DENSITIES IN GRAIN SORGHUM

Six methods for sampling field populations of ovipositing sorghum midge, Contarinia sorghicola, in grain sorghum panicles were compared to an absolute sampling method. The methods evaluated were the visual, tap, remove, shake, beat-bucket, and grab. Population estimates obtained by visual examination were similar to absolute estimates when population density was low but significantly differed at mean midge densities above 9.2/panicle. The remaining sampling method density estimates were significantly less than the absolute method estimates. The visual examination method was relatively time efficient taking ca. one minute per panicle to complete. The effect of panicle compactness (open, medium, and compact) on the precision of the visual examination was investigated. Accuracy of the visual examination method significantly decreased as panicle compactness increased. This may be a result of either obstructed vision or increased density of midges with compactness or a combination of both.