Energy Thresholds for Mid-Infrared Thermal Control of Weed Seeds and Plants

Non-chemical weed management is essential for advancing integrated weed management systems. Mid-infrared (MIR) radiation (3–50 µm) is a promising approach for heat-based thermal weed control with minimal fire risk. The lethal MIR energy requirement may be influenced by plant species, growth stage, and seed size. However, no published research has quantified the MIR energy dose (J cm -2 ) needed to control either weed seeds or various plant species at different growth stages. This study evaluated a dose range of 0–109 J cm -2 to identify minimum mid-infrared (MIR) energy thresholds required to control six species at the 3-, 6-, and 9-leaf growth stages, as well as dry and imbibed seeds of nine species. Responses were described using regression models based on dry biomass, survival, and reductions in viability. Overall responses varied across species, with smaller broadleaf weeds being most susceptible. Palmer amaranth was highly sensitive, requiring 13 and 56 J cm -2 to reduce biomass by 90% at the 3- and 6-leaf stages, respectively, while Italian ryegrass was highly tolerant, with 109 J cm -2 failing to achieve a 90% biomass reduction. Across all species, plants at the 9-leaf stage were highly tolerant, with no treatment achieving a 90% reduction. Dry Palmer amaranth seeds were the most tolerant, requiring 100 J cm -2 to reduce viability by 50%, compared with 8 J cm -2 for imbibed seeds. Conversely, dry barnyardgrass seeds were more susceptible, requiring just 16 J cm -2 for 50% viability reduction compared to 31 J cm -2 when imbibed. Seed size was moderately and positively correlated with the energy required for 50% viability reduction (r = 0.58). This study provides evidence that MIR radiation can serve as an effective thermal weed control tool, while also highlighting that efficacy varies among species, likely due to differences in morphology and physiology.