Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 12, 1999
Publication Date: February 7, 2000
Citation: Johnson, W.C. 2000. Interference and economic threshold of yellow nutsedge with peanut. Weed Science Society of America Abstracts. 40:39. Technical Abstract: Yellow nutsedge is one of the most common and troublesome weeds of peanut production. Losses from yellow nutsedge in peanut include yield reduction, foreign material contamination, and costs of control. However, there is evidence that yellow nutsedge is not very competitive with peanut. Studies were conducted from 1997 to 1999 in Tifton, GA to measure the full-season interference of yellow nutsedge in peanut using a response prediction experiment with a natural infestation of yellow nutsedge. 'Georgia Green' peanut was seeded in May each year, and plots were established immediately after crop emergence. Plots were 1.8 m by 1.8 m and replicated six times. Yellow nutsedge plants were counted four weeks after crop emergence in each plot, and six weed-free plots were randomly established. Yellow nutsedge densities ranged from 0 to 164 plants/m2. Regression analysis showed a 27% reduction in peanut yield with a yellow nutsedge infestation of approximately 90 plants/m2, with less yield reduction at higher yellow nutsedge densities. Data also indicated a significant three-way interaction among yellow nutsedge density, tuber contamination, and peanut yield that showed more tuber contamination occurring at high peanut yields. Estimates of economic thresholds were calculated based on three control options; imazapic (most costly), bentazon, and metolachlor (least costly). Economic thresholds were also calculated based on peanut with different yield potentials. With a yield potential set at 3140 kg/ka (1998 Georgia state yield average), yellow nutsedge economic thresholds were calculated at 7, 4, and 3 plants/m2 for control with imazapic, bentazon, and metolachlor, respectively. Greater yield potentials lowered the economic threshold, while lower yield potentials increased the economic threshold.