Mapping Spring Dead Spot Using Visible and Near Infrared Reflectance for Precision Management.

Successful management of bermudagrass in marginal regions of adaptation is limited by the development and persistence of spring dead spot (SDS). Patches frequently appear in the same locations from year to year, but are difficult to control. Fall applications of tebuconazole are common because it is economical and typically effective at suppressing SDS over time. Alternative active ingredients may have greater efficacy but are less viable options for fairway applications because of cost. The generation of maps to monitor SDS epidemics may be useful for precision turf management. Fungicide applications based on geographic severity can allow turf mangers to limit total treatable acreage and reduce costs. Additionally, such maps may help turf managers identify underlying problems that contribute to SDS, therefore increasing the probability of successful management with cultural practices. The objective of this research is to explore options for SDS mapping with equipment-mounted and aerial sensors. Ground truth data were collected in 2014 and 2015 from eleven fairway locations in Virginia and North Carolina by obtaining GPS coordinates of SDS patches by complete or systematic sampling. Reflectance data were continuously collected using a cart-mounted Holland Scientific ACS470 in the red (670nm) red-edge (730nm) and near-infrared NIR (760nm) and transformed using the ratio vegetation index (RVI:  NIR/Red). Reflectance data were overlaid with SDS coordinates, with a random subset of ground truth samples retained for accuracy assessments. Aerial imagery was collected following data collection of two fairway locations with an unmanned aerial system (Inspire 1, DJI, Los Angeles, CA) and georectified with SDS coordinates. Ground-based and aerial imagery provided a rapid documentation of SDS epidemics on golf fairways.