What Can I Use to Kill Pigweed?

Manual Method

• If you have a small infestation of pigweed, mechanical control should take care of it. Use a garden tiller or scuffle hoe as soon as you see the weed emerging from the soil. If you wait too long, the pigweed develops deeper roots, making it more challenging to remove. Wait 10 days and hoe the area again to remove any pigweed that may have germinated. Hoe a third time 10 days later.

Organic Method

• Soil solarization is a process whereby the summer sun's heat destroys soil-borne pathogens and weeds. While it doesn't kill all weeds, solarization destroys those in the top few inches of soil. The process is easy but time-consuming. Mow down any weeds protruding from the soil, remove debris and rake the soil smooth. Water the soil until it's soaked to at least 6 inches. Stretch thin, transparent plastic over the area and hold it in place by either burying the edges with soil or using bricks or rocks to hold it tight. The plastic must be tight enough against the soil to prevent air from coming in. To kill pigweed, the soil needs to reach 115 degrees Fahrenheit and maintain that temperature for three to four weeks.

Chemical Method

• The key to fighting pigweed infestations with herbicides is to get it while it's young. Pigweed has the ability to grow several inches a day, according to scientists at the University of Georgia, so you'll need to keep a constant watch for signs of germination. Farmers have good results using an herbicide with the active ingredients S-metolachlor + Sodium Salt of Fomesafen, at one quart per acre. Two weeks later, apply a glyphosate herbicide. Sometimes the first herbicide damages the pigweed enough that the glyphosate can finish the job. Read the herbicide labels completely and follow application rates and instructions.

Considerations

• Pigweed is a summer annual weed that aggressively reseeds. Native to the Sonoran Desert, it flourishes in the southern portion of the United States, from California to Virginia. While other plants fade in the heat, pigweed thrives, providing competition to turfgrasses, vegetable crops and ornamentals. Timing is critical when attempting to control pigweed, either with the sun's heat or chemicals. Get it out of the soil before it produces a taproot and seeds.