Tomato tolerance to preemergence herbicides in plasticulture using narrow bands and precision technology

Abstract

Preemergence (PRE) herbicides are broadcast-applied over the entire top of raised beds prior to plastic mulch installation. Following mulch installation, broadleaves and grasses only emerge from the planting holes. For this reason, the majority of PRE herbicides that are broadcast-applied underneath the plastic mulch are unnecessary for weed control. To reduce off-target herbicide application, we evaluated (1) tomato tolerance to herbicides applied in narrow bands over the planting holes at 2 weeks after transplant (WATP), and (2) tomato tolerance to herbicides that were precisely applied to individual planting holes immediately prior to transplant using a precision herbicide applicator that was previously developed at the University of Florida. Halosulfuron, metribuzin, pendimethalin, and S-metolachlor applied in narrow bands over the planting holes at 2 WATP did not significantly injure tomato, stunt growth, nor reduce yield. However, significant tomato injury (7%) was observed when fomesafen was applied in narrow bands over the planting holes where tomato plants have been transplanted for 2 weeks. Precision application of fomesafen, metribuzin, oxyfluorfen, and S-metolachlor in a carrier volume of 187, 374, or 561 L ha−1 using the precision hole-punch sprayer to the individual planting holes prior to transplant caused minimal early-season tomato injury (≤4%) and did not significantly stunt tomato plant growth or reduce yield. Overall, results demonstrated a safe and effective way to reduce off-target herbicide application in plastic-mulched tomato by applying herbicides in bands over the planting holes after transplant or precisely applying herbicides to individual planting holes prior to transplant using a precision hole-punch applicator.