Early Season Peanut Weed Control

Peanut planted 3 weeks ago on a dry-land field in Jackson County. Credit: Josh Thompson

The weather in May has been hot and dry across the panhandle. A hot, dry May combined with late cold fronts in April has proven to be a challenge for peanut growers trying to get their crop planted. Many have had to postpone planting due to a lack of soil moisture. The peanuts that were planted 2-3 weeks ago are up and growing, and so far have had little weed pressure to compete with.

Without water to activate pre-emerge herbicides, however, there is bound to be a major flush of weeds once the first rain comes. To be prepared, plan on using a good post-emerge herbicide program for weed control.

Some of the best early post-emergence chemicals are paraquat (Gramoxone etc.) and s-metolachlor (Dual Magnum, etc.).

Gramoxone is non-selective and does very well at controlling many weeds, including pigweeds, coffee weed, and beggarweed. It has no soil activity and does not translocate well through plants so only tissue that contacted with the chemical will be burned.

Since this chemical is non-selective, it will cause peanut leaves to burn and fall off, after which they quickly put on new leaves continue to grow. When Gramoxone is applied between true ground-cracking and 28 days after cracking, peanut yield will not be reduced. Research on this topic from the University of Florida and University of Georgia has continuously shown no yield reduction when applied during this window.

Some growers choose to add Basagran to the tank to lessen the burn of the Gramoxone on peanuts. Consequently, it will lessen the burn on the weeds as well and can therefore reduce weed control. If adding Dual Magnum to the application, Basagran may be a necessary additive since the combination of Dual and Gramoxone will have greater burn on peanut.

Adding Dual Magnum to a Gramoxone application is advised because it will add soil residual activity to the mix, helping to control weeds before they emerge. Dual Magnum provides good activity on hard to kill weeds such pigweeds and Florida pusley and will pick up where at-plant and pre-plant applications left off.

The timely application of Gramoxone plus Paraquat should control many emerged weeds and provide excellent residual control before making layby herbicide applications. For more information on weed control in peanuts, see Weed Management in Peanuts 2013 or Control of Palmer Amaranth in Agronomic Crops.