Tomato and Bell Pepper Tolerance to Preemergence Herbicides Applied Post-Transplant in Plasticulture Production


 Preemergence (PRE) herbicides are often banded over the entire top of raised beds for broadleaf and grass control in plasticulture vegetable production systems. However, broadleaf and grass weeds only emerge from the planting holes and tears in the plastic mulch. Banded application results in herbicides applied where no holes occur and therefore where they are not needed. Our objective is to identify herbicides that do not harm transplanted crops when directed at transplant holes post-transplant (POST) with the aim to reduce off-target applications. Therefore, we evaluated tomato and pepper tolerance to PRE herbicides applied to transplant holes 2 weeks after transplant and the subsequent effects on crop tolerance and weed density. Halosulfuron, S-metolachlor, metribuzin, and pendimethalin did not injure tomato transplants, reduce height, or reduce yield. Fomesafen caused some tomato injury (7%) but had no effect on other measured parameters in Trial I. All PRE herbicides injured peppers (≥19%) though no effect on yield was observed. Overall, halosulfuron, S-metolachlor, metribuzin, and pendimethalin can be safely applied to tomato transplant holes two weeks after transplant with no significant crop injury nor effects on final yield, but none of the evaluated herbicides are safe for use in pepper.