Complex sentence: Palmer amaranth is considered a threat most specifically to the production of cotton and soybean crops in the southern United States because in many places, the plant has developed resistance to glyphosate since at least 2006, a widely used broad-spectrum herbicide.
Split into simpler sentences: Palmer amaranth is considered a threat most specifically to the production of cotton and soybean crops in the southern United States. In many places, the plant has developed resistance to glyphosate since at least 2006, a widely used broad-spectrum herbicide.