Using NDVI to estimate variable aphid populations in sorghum, within the context of entomology research, shows promise and problems

Melanaphis sorghi is a major pest of sorghum around the world and recently in North America. This aphid is challenging to monitor in the field due its variable distribution and preference for the underside of sorghum leaves. Sorghum producers and agricultural entomologists would benefit from remote sensing technologies, such as an uncrewed aerial systems (UAS), which could accurately estimate pest densities in the field. We conducted an experiment using a UAS to examine the relationships between aphid pressure, NDVI, and yield in sorghum. We also conducted an experiment using insect exclusion cages, a common tool in field entomology experiments, to regulate aphid densities paired with UAS imagery. Both experiments were able to associate NDVI to aphid densities and yield estimates. However, relationships were generally weak and sometimes counter to expectations and past research within this system. UAS technology is more than capable of detecting aphids in sorghum, but issues related to aphid-plant interactions and variability within the field make their implementation in research difficult.