Influence of Distance from Source and Height Above Canopy on Palmer Amaranth Pollen Distribution


The spread of glyphosate-resistant Palmer amaranth (Amaranthus palmeri S. Wats) germplasm through pollination makes managing this weed challenging. The objective of this study was to determine Palmer amaranth pollen dispersal under prevailing field conditions at various heights above cotton (Gossypium hirsutum L.) or soybean [Glycine max (L.) Merr.] canopies within 50 m of pollen-source plants. On four days in 2008 and 15 days in 2009, Palmer amaranth pollen was collected in a compass rose array of traps at the top of the crop canopy or 1, 2, or 3 m above the canopy at distances of 1, 2, 10, 25, and 50 m from a densely planted pollen source. Pollen was found at the outermost extremities of the trap array (50 m laterally and 3 m above the crop canopy) indicating that Palmer amaranth pollen dispersion likely extend beyond the area considered in this study. Eighty-two percent of pollen captured was within 2 m of the source while 5 to 7% was captured 10 to 50 m from the source. Seventy-five percent of pollen was captured at canopy level (0.75 m above soil surface) with 10% or less at 1, 2, and 3 m above the canopy. Data did not consistently correlate with relative humidity, dew point, ambient temperature, prevailing wind direction, or wind speed.

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Crop Management