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Iowa State University

Soybean

Entomology

Agronomy Publications

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Reduction In Common Milkweed (Asclepias Syriaca) Occurrence In Iowa Cropland From 1999 To 2009, Robert G. Hartzler Dec 2010

Reduction In Common Milkweed (Asclepias Syriaca) Occurrence In Iowa Cropland From 1999 To 2009, Robert G. Hartzler

Agronomy Publications

The role of common milkweed in the lifecycle of the monarch butterfly has increased interest in the presence of this weed in the north central United States. An initial survey conducted in 1999 found that low densities of common milkweed occurred in approximately 50% of Iowa corn and soybean fields. In 2009, common milkweed was present in only 8% of surveyed fields, and the area within infested fields occupied by common milkweed was reduced by approximately 90% compared to 1999. The widespread adoption of glyphosate resistant corn and soybean cultivars and the reliance on post-emergence applications of glyphosate for weed ...