Palmer amaranth (Amaranthus palmeri), a member of the "pigweed" family, is one of the most troublesome weeds in many southern row crops. Seed can germinate all season and plants can grow to over 6 feet in height. Plants have either male flowers that shed pollen or female flowers that can produce up to 600,000 seed per plant. One Palmer amaranth per 30 foot of row can reduce cotton yield by 6 to 12%.

In recent years, an increased number of cases of injury from herbicide residue in straw/hay, manure, and compost have been diagnosed in the Virginia Tech Plant Disease Clinic. Growers are surprised and dismayed to learn that manure, straw, mulch, or other amendments intended to improve their garden or landscape might have such unforeseen consequences. Of particular concern to organic growers are herbicide residues.

Grassy weeds in pastures and hayfields compete with desired forage species and reduce the productivity of forage systems. Lack of selective herbicides makes grassy weed species, such as Johnsongrass, Japanese stiltgrass, broomsedge, and foxtail species difficult to control. Proper soil fertility, grazing management, and correct timing and placement of herbicide application can effectively control these species.