Palmer Amaranth (Amaranthus palmeri)

About Palmer Amaranth:

Palmer Amaranth is an annual weed that is commonly known as Palmer Pigweed. If the weed is not managed properly, this extremely aggressive weed can greatly reduce the yield of your crops. The major problem with this weed is that it produces a large taproot that can easily enter hard soil, reaching water and nutrients that other plants cannot. If Palmer Amaranth lives in ideal conditions, it can grow several inches in one day.

Family: Amaranth family (Amaranthaceae)

Palmer Amaranth Prevention:

Palmer Amaranth typically grows between 6 to 8 feet but occasionally can grow up to 10 feet or taller. The stems and leaves of this weed are smooth, with minimal to no hair on it. The leaves have a very predominate pointed tip, almost diamond shaped, and are arranged symmetrically around the stem. Interestingly enough, Palmer Amaranth weeds look like poinsettia when looked at from above. The Palmer Amaranth can be either male or female. Both plants have inflorescence spikes that can grow from 6 to 36 inches long with the seed head being the main and longest terminal. The female plants have rigid, sharp, small spines with a bristly texture around the outside of the flower and painful bracts. Male plants are decently soft to the touch, they have anthers and produce pollen.

Common locations

• - Hot climates
• - Veritable fields
• - Soybean fields
• - Corn fields
• - Peanut fields
• - Cotton fields

Palmer amaranth Prevention and Control:

Make sure that your pre-emergent herbicide application is activated by either irrigation or rainfall. If these pre-emergent herbicides are not activated, no control will be provided for Palmer Amaranth. Depending on the field Palmer Amaranth has entered will determine what pre-emergent controls work best. Palmer Amaranth is resistant to herbicides that have glyphosate and ALS in them. It is important that you apply these herbicides before Palmer Amaranth reaches 6 feet. As soon as this plant reaches 6 feet or taller, it is almost impossible to control by post-emergent herbicides. In the end it might be necessary to try conventional tillage followed by herbicides and/or adding corn into your crop rotation.

Corn

Herbicides with Atrazine can take control over Palmer Amaranth when it is applied to corn, at a max rate of 2.5 lb ai/A/yr if it is applied at two timings for pre-emergent control. If you are looking for early post-emergent control in your corn field, Atrazine plus prowl or Glyphosate plus Atrazine and finally liberate 280 plus Atrazine works well. If needed, there are herbicides able to control Palmer Amaranth in late post-emergent control such as 2,4-D or Banvel/Clarity.

Cotton

For an infested cotton field, application of Banvel/Clarity, Direx, Reflex or Valor provides effective control for 15 to 30 days. It is important to follow this first application with Cotoran, Direx, Prowl or Sraple at the time of planting. You may also do a hooded application of Paraguat or Paraquat plus Caparol to eradicate Palmer Amaranth.

Peanut

In peanut fields, the best pre-emergent control is a burn-down program that contains 2,4-D to make sure that Palmer Amaranth does not emerge before planting. Applying Valor or Valor plus Prowl can also work for pre-emergent control. There is some control that can be done when Palmer Amaranth has just started to grow using a combination of Paraquat plus Dual Magnum and/or Basagran. Another great prevention is to plant your peanuts in twin rows. This will provide shade to the soil much earlier in the season then planning wider rows, which in turn will hopefully suppress the germination and growth of Palmer Amaranth.

Soybeans

Just as peanuts, soybeans should also be planted in narrow rows that are about 15 to 7.5 inches apart. As it is stated above, these narrow rows provide shade which will help prevent Palmer Amaranth seeds from germinating. For pre-emergent control, use roundup ready herbicides such as Valor or Sulfentrazone. For post emergent control, use roundup ready herbicides like Dual Magnum plus Reflex, Cobra, Ultra Blazer, or Pursuit to manage Palmer Amaranth.

Latin / Alternative Palmer Amaranth names:

• - Amaranthus palmeri
• - Palmer pigweed
• - Carelessweed

Additional Palmer Amaranth Resources