Continuous planting of lettuce from December to September each year in the Salinas Valley of California requires preparation of raised fallow beds ready for planting. Application of soil residual herbicides during winter fallow periods controls weeds but must be used with caution because germinating lettuce seedlings are very sensitive to herbicide soil residues. Three herbicides were applied to fallow beds at about 90, 60, and 30 d before lettuce was seeded. Herbicides tested were flumioxazin at 71, 105, and 211 g ai ha−1, two formulations of oxyfluorfen each at 280 and 560 g ha−1, and carfentrazone at 36 g ha−1. Herbicide injury to lettuce was assessed by visual estimates, crop stand, and number and weight of marketable lettuce heads. The 71 g ha−1 rate of flumioxazin, both oxyfluorfen formulations, and carfentrazone did not injure seeded lettuce or reduce the number or weight of lettuce heads. Flumioxazin at 211 g ha−1 injured lettuce, reducing the number of marketable heads, and should not be used within 90 d of lettuce planting.
Nomenclature: Carfentrazone; flumioxazin; oxyfluorfen; lettuce, Lactuca sativa L