Successful reduced tillage production in peanuts requires a weed-free seedbed when peanuts are emerging and throughout the first 6 weeks of the season (often referred to as the critical period of weed interference.) Dogfennel, marestail (horseweed), and emerged summer weeds need to be killed before peanuts emerge. There are no effective herbicides to control dogfennel and marestail once peanuts emerge. Strongarm has some activity on both weeds when they are up, but it gives 50% control at best. The key is success prior to peanut emergence.

A month ago, 2,4-D was a good option that suppresses these weeds. There is no magic combination for a single application. My recommendation for dogfennel at this point is a high rate of glyphosate and then a high rate of paraquat three to four days later (if you are trying to plant soon.) I don’t think a mixture of both herbicides is as effective as sequential applications of glyphosate followed by paraquat.

In the photograph you see not only a winter weed but a small Palmer amaranth plant that has already emerged. There are also fields with common ragweed that have emerged by this point in the spring. Glyphosate likely will not control either one of these weeds in many fields. Paraquat is extremely important in killing these weeds in reduced tillage systems. Glufosinate (Liberty) came up in a conversation about burndowns. The context was glufosinate plus glyphosate. This is a broad-spectrum mixture, but the glufosinate will likely antagonize glyphosate activity on some weeds. There are also some populations of Palmer amaranth resistant to glufosinate across the state.

This brings me back to paraquat. While it is available, we need to use paraquat in burndowns as much as possible. That’s why I recommend the one-two punch of glyphosate then paraquat prior to peanut emergence.