As you make burndown weed control decisions for 1999, make sure that you fully understand all of your herbicide options.

Gramoxone Extra, Touchdown and glypho­sate (Roundup) rely on different modes of action, so it’s important to tailor your specific herbicide decisions to the needs of your fields.

Answers Vary

“Weed species and growth stage determine the type of herbicide that’s most appropriate,” says Bob Harzler, weed scientist at Iowa State University. “If you’re going after perennials, Touchdown or glyphosate is usually the better choice because of their systemic mode of action.”

However, the contact activity of Gramoxone enables the herbicide to offer a greater speed of activity, as well as effective control of annual and small perennial weeds. This contact non-selective herbicide works on contact with plant foliage, attacking weeds and completely controls them within 24 to 48 hours.

“It’s known for reliability, speed of activity and its ability to work in cool, dry weather,” says Chuck Foresman, Zeneca Ag Products technical business lead for non-selection herbicides.

Touchdown and glyphosate are systemic non-selective herbicides which are absorbed through leaves and translocated to the growing points of the plant. Over time, they inhibit amino acid synthesis in the plant.

While both are systemic burndown herbicides, there are distinct differences.

“The active ingredient in Touchdown is sulfosate, which contains a different salt of PMG acid than glyphosate,” says Foresman. “This difference helps Touchdown provide some contact burndown activity as well as systemic activity.”

Foresman says to expect initial activity on annual weeds…