Natural enemy composition drives error rates for sorghum aphid dynamic thresholds

IPM sampling plans are primarily focused on pest abundance estimates or classification. With few exceptions, little information exists on integrating natural enemy estimates into already existing protocols. Since the 2013 sorghum aphid (Melanaphis sorghi) outbreak, natural enemy impact has been extensively studied in the US Southern Plains. Studies indicate that natural enemies are providing top-down suppression of M. sorghi, and the combination of all parasitoids and predators combined appears to be critical for preventing aphids from reaching economic injury levels. Preliminary dynamic thresholds have been calculated from empirical field data and controlled experiments. These preliminary thresholds are awaiting field validated. Therefore, the objective of this study was to quantify whole-field error rates for sorghum aphid dynamic thresholds in Texas and Oklahoma. For this study, seasonal sampling data for multiple grain sorghum field locations was used to document percentages of correct predictions and errors relative to aphid populations exceeding economic injury levels. Error rates appear to be driven by the composition of natural enemies, rather than the ratio of natural enemies to aphids. Additional multi-year multi-location data is continuously being collected and validated with the objective of creating reliable integrated sampling plans.