Vegetable response to sulfentrazone soil residues at four planting intervals

Sulfentrazone was recently granted food-use tolerance approval for use on Brassica head and stem, as well as Brassica leafy vegetables. To date, one sulfentrazone registrant has listed those crops on its use label. In coastal California multiple crops per year including Brassica vegetables are grown in rapid succession; therefore, to avoid injury to rotational crops, herbicides used in those fields must be carefully selected. Given concerns about the relatively long soil persistence of sulfentrazone, studies were conducted to measure the response of direct-seeded carrot, lettuce, onion, spinach, and seeded tomato planted 3, 6, 9, and 12 mo after sulfentrazone application at 0, 112, 224, and 336 g ai ha–1. Eight plant-back studies were conducted during 2010–11 and 2012–13. Data collected were injury estimates, and stand and dry weights. Results indicate that it is safe to plant carrot and tomato 3 mo after sulfentrazone application at rates up to 336 g ai ha–1. Lettuce and green onion should not be planted within 9 mo of sulfentrazone application. Spinach should not be planted within 12 mo of sulfentrazone application. Nomenclature: Sulfentrazone; carrot; Daucus carota subsp. Sativus (Hoffm.) Schübl. & G. Martens; lettuce; Lactuca sativa L.; onion; Allium cepa L.; spinach; Spinacia oleracea L.; tomato; Lycopersicon lycopersicum (L.) Karsten L. esculentum (L.) Mill.