An Evaluation of Targeted Spraying for Reducing Herbicide Use in Highbush Blueberry

Herbicides are the most common method for weed control in berry crops, although the evolution of herbicide resistance, worker and crop safety concerns, and regulatory challenges associated with the prevention of off-target movement are driving interest in alternative weed management technologies. Optically guided, targeted spray systems show promise for reducing herbicide use, minimizing crop damage, and expanding weed control options in perennial crops. In 2021 and 2022, field trials were conducted in New Jersey to evaluate the impact of conventional banded and targeted (WEED-IT™ system) herbicide applications on weed control and crop outcomes. Control of common groundsel, horseweed, and common purslane was influenced by herbicide type and application strategy but not by their interaction. Fluroxypyr applied at 280 and 560 g a.e./ha provided similar or better control of common groundsel and common purslane (>90%) compared with the 2,4-D choline and glufosinate (71% to 92%) standards. Similarly, horseweed control with florpyrauxifen-benzyl applied at 30 and 60 g a.e./ha (80% to 91%) matched or exceeded the suppression provided by 2,4-D and glufosinate (62% to 87%). Herbicide applications using the WEED-IT™ system reduced herbicide use by approximately 50% but provided less weed control than the traditional banded method; results likely reflect the effects of crop size and density on spray coverage. Crop injury was primarily observed on new canes, with targeted applications causing slightly more damage than the banded treatments across all observation timings. Stunting of new blueberry canes exceeded 8% at 1 week after application and decreased to less than 1% by 4 weeks after application, compared with a maximum of 3% stunting from banded applications. The greater levels of observed crop damage probably result from the system’s inability to distinguish between crops and weeds. Despite the potential of targeted spraying technologies to reduce herbicide use, their effectiveness and safety in perennial crops warrant further research, particularly regarding integration into comprehensive weed-management programs.