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Title: POST weed control using halosulfuron in direct-seeded watermelon

Author
item SHREFLER, JAMES - OSU, LANE, OK
item BRANDENBERGER, LYNN - OSU, STILLWATER, OK
item Webber Iii, Charles
item ROBERTS, WARREN - OSU, LANE, OK
item PAYTON, MARK - OSU, STILLWATER, OK
item WELLS, LYNDA - OSU, STILLWATER, OK

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2007
Publication Date: 10/1/2007
Citation: Shrefler, J.W., Brandenberger, L., Webber III, C.L., Roberts, W., Payton, M.E., Wells, L. 2007. Post weed control using halosulfuron in direct-seeded watermelon. Weed Technology. 21:851-856.

Interpretive Summary: Watermelon (Citrullus lanatus) production in central regions of the United States may occur during mid to late summer after the typical market price decline. Expected market prices at this time of year may not justify the expense of intensive production inputs such as plastic mulch or hoeing, practices which contribute to weed control. Therefore, other weed control options are needed. Several herbicide options are available for use at the time of planting; and combinations of herbicides have been used to broaden the spectrum of weed control in melon crops. Field studies were conducted over 4 yrs in Oklahoma to determine efficacy and crop response of postemergence (POST) halosulfuron applications to direct-seeded watermelon that received preemergence application of ethalfluralin at 840 g ai/ha. At 5 weeks after crop emergence (WAE) halosulfuron was applied at 18, 27, 36, and 54 g ai/ha. The 27 g ai/ha rate was also applied at 1, 2, 3 and 7 WAE. Halosulfuron applications made 5 WAE did not provide acceptable (>80%) control of pigweeds [Palmer amaranth (Amaranthus palmeri S. Wats.) and tumble pigweed (Amaranthus albus L.)] and cutleaf groundcherry (Physalis angulata L.) regardless of rate. Applications made 1 WAE provided significantly greater control of pigweeds and cutleaf groundcherry than did later applications. Neither treatments made 5 WAE with halosulfuron at 36 and 54 g ai/ha, nor treating at 1, 2 and 3 WAE, resulted in significantly different yields than hand-weeded watermelon. These studies show that POST halosulfuron application may be a useful treatment for direct-seeded watermelon. Watermelon growers who rotate crops to avoid disease problems do not always know what weed species to expect, thus POST treatment with halosulfuron would offer an opportunity to respond to emerging weeds on an as-needed basis. This option would enable more judicious use of herbicides and possible reduction in production costs.

Technical Abstract: Weed control is needed in watermelon (Citrullus lanatus) production to avoid losses in crop yield and marketability that result from weed interference. Not only does weed control provide direct benefits to crop yields, but uncontrolled weeds hamper the management of insect and disease pests and reduce harvest efficiency. Field studies were conducted over 4 yrs in Oklahoma to determine efficacy and crop response of postemergence (POST) halosulfuron applications to direct-seeded watermelon that received preemergence application of ethalfluralin at 840 g ai/ha. At 5 weeks after crop emergence (WAE) halosulfuron was applied at 18, 27, 36, and 54 g ai/ha. The 27 g ai/ha rate was also applied at 1, 2, 3 and 7 WAE. Halosulfuron applications made 5 WAE did not provide acceptable (>80%) control of pigweeds [Palmer amaranth (Amaranthus palmeri S. Wats.) and tumble pigweed (Amaranthus albus L.)] and cutleaf groundcherry (Physalis angulata L.) regardless of rate. Applications made 1 WAE provided significantly greater control of pigweeds and cutleaf groundcherry than did later applications. Neither treatments made 5 WAE with halosulfuron at 36 and 54 g ai/ha, nor treating at 1, 2 and 3 WAE, resulted in significantly different yields than hand-weeded watermelon. These studies show that POST halosulfuron application may be a useful treatment for direct-seeded watermelon. Watermelon growers who rotate crops to avoid disease problems do not always know what weed species to expect, thus POST treatment with halosulfuron would offer an opportunity to respond to emerging weeds on an as-needed basis. This option would enable more judicious use of herbicides and possible reduction in production costs.