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Title: Injury potential from carryover of watermelon herbicides residues

Author
item BRANDENBERGER, LYNN - OSU, STILLWATER, OK
item SHREFLER, JAMES - OSU, LANE, OK
item Webber Iii, Charles
item TALBERT, RONALD - UNIV OF ARKANSAS
item PATON, MARK - OSU, STILLWATER, OK
item WELLS, LYNDA - OSU, STILLWATER, OK
item MCCLELLAND, MARILYN - UNIV OF ARKANSAS

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2006
Publication Date: 8/1/2007
Citation: Brandenberger, L., Shrefler, J.W., Webber III, C.L., Talbert, R.E., Paton, M.E., Wells, L.K., McClelland, M. 2007. Injury potential from carryover of watermelon herbicides residues. Weed Technology. 21(2):473-476.

Interpretive Summary: New herbicides for use in vegetable crops must be evaluated for effectiveness and safety to the crop in which they are to be used, as well as to rotational crops. Herbicides used in summer crops may leave chemical residues in the soil that can damage late summer, fall, and winter planted crops. Watermelon (Citrullus lanatus) crops in Oklahoma and Arkansas are frequently followed in the fall by wheat (Triticum aestivum) or spinach (Spinacia oleracea) and occasionally by cabbage (Brassica oleracea var. capitata), and broccoli (Brassica oleracea var. botrytis). The purpose of these studies was to determine the rotational crop safety in broccoli, cabbage, spinach, and wheat of carryover from halosulfuron used alone and in combination with other herbicides and sulfentrazone used alone in preceding crops. Studies were conducted at three sites during a 2-yr period in Oklahoma and Arkansas to determine the rotational crop safety of residues from herbicides used in preceding watermelon crops. Herbicide treatments were applied to previous watermelon crops 14 to 26 weeks prior to planting rotational crops. Herbicide treatments included halosulfuron, ethalfluralin, sulfentrazone alone; halosulfuron tank-mixed with bensulide, clomazone, ethalfluralin, naptalam; tank-mix of naptalam and bensulide. The rotational crops evaluated included spinach ('Cypress'), broccoli ('Everest' and 'Green Sprouting Calabrese'), cabbage ('Early Jersey Wakefield'), and wheat ('Jagger'). Spinach was the rotational crop whose emergence was most affected by herbicide carryover in these studies. Injury to rotational crops after emergence was exhibited as crop stunting by spinach, broccoli, and cabbage. Stunting was highest for spinach with significant injury resulting from sulfentrazone and a majority of treatments containing halosulfuron. Broccoli and cabbage were also sensitive to halosulfuron alone at higher rates and to tank-mixes of clomazone + ethalfluralin + halosulfuron. Wheat was not injured after emergence by carryover from herbicides included in the study. Recommendations include a minimum 12-month plant-back interval for spinach, cabbage and broccoli after use of halosulfuron or sulfentrazone.

Technical Abstract: Summer watermelon (Citrullus lanatus) crops produced in the south-central United States are often followed by fall rotational crops such as cool-season vegetables and winter wheat (Triticum aestivum). Herbicides used in summer crops may leave chemical residues in the soil that can damage late summer, fall, and winter crops. Studies were conducted at three sites during a 2-yr period in Oklahoma and Arkansas to determine the rotational crop safety of residues from herbicides used in preceding watermelon crops. Herbicide treatments were applied to previous watermelon crops 14 to 26 weeks prior to planting rotational crops. Treatments included halosulfuron, ethalfluralin, sulfentrazone alone; halosulfuron tank-mixed with bensulide, clomazone, ethalfluralin, naptalam; tank-mix of naptalam and bensulide. The rotational crops evaluated included spinach (Spinacia oleracea), broccoli (Brassica oleracea var. botrytis), cabbage (Brassica oleracea var. capitata), and wheat. Spinach ('Cypress') was the rotational crop whose emergence was most affected by herbicide carryover in these studies. Injury to rotational crops after emergence was exhibited as crop stunting by spinach, broccoli ('Everest' and 'Green Sprouting Calabrese'), and cabbage ('Early Jersey Wakefield'). Stunting was highest for spinach with significant injury resulting from sulfentrazone and a majority of treatments containing halosulfuron. Broccoli and cabbage were also sensitive to halosulfuron alone at higher rates and to tank-mixes of clomazone + ethalfluralin + halosulfuron. Wheat ('Jagger') was not injured after emergence by carryover from herbicides included in the study. Recommendations include a minimum 12-month plant-back interval for spinach, cabbage and broccoli after use of halosulfuron or sulfentrazone.