Submitted to: Western Society of Weed Science Research Reports
Publication Type: Research Notes
Publication Acceptance Date: 12/1/2005
Publication Date: 3/1/2006
Citation: Boydston, R.A., Parker, R. 2006. Crop response to carfentrazone applied preemergence. Western Society of Weed Science Research Reports. Pp. 41-42.
Technical Abstract: Carfentrazone was recently labeled for preemergence use in over twenty different annual vegetables. Soil activity of carfentrazone was tested in green house trials with six crops planted at various times in relation to herbicide application date. Carfentrazone was applied at 0.03 lb ai/a alone or in combination with DCPA at 5.3 lb ai/a in flats containing a loamy sand soil containing <1% organic matter. Five crops (lettuce, cabbage, broccoli, sugar beet, and onion) were seeded corresponding to six, four, and two days prior to herbicide application, immediately after herbicide application, and 7 days after herbicide application. Onion and sugar beet were also seeded again at 22 days after herbicide application. All crops were severely injured and the number of live seedlings reduced by carfentrazone applied at 0.03 lb ai/a or carfentrazone at 0.03 lb ai/a plus DCPA at 5.3 lb ai/a regardless of planting date. Lettuce emerged sooner than other crops and most plants had emerged within 3 days of planting. Lettuce seedlings that were emerged at the time of carfentrazone application (from the first two planting dates) were killed. Lettuce stand was not reduced when planted 7 days after carfentrazone application, but surviving plants were necrotic with malformed growth and smaller compared to nontreated checks. Broccoli, cabbage, and sugar beet emerged in 2 to 5 days after planting. Broccoli, cabbage, and sugar beet were all severely injured and stands nearly eliminated by carfentrazone or carfentrazone plus DCPA at all planting dates. Onion stand was severely reduced by both herbicide treatments at all planting dates. Onions that survived herbicide treatments were usually stunted and chlorotic and often died within a week or two after emergence. About 10% of onions survived and eventually some plants grew normally. Onions and sugar beets planted 22 days after carfentrazone application, were severely injured and plant stand reduced by 82 and 86%, respectively. Carfentrazone has the potential to injure many small seeded vegetable crops when applied preemergence on mineral soils containing low amount of organic matter.