Dogfennel Control is a Challenge Peanut Notes No. 42 2019
Dogfennel can be almost impossible to control once peanuts emerge. Based on research conducted many years ago in a pasture setting, Strongarm applied postemergence was the most effective herbicide labeled in peanut, and at the recommended use rate it only controlled this weed about 50%. The other herbicides we generally use (Gramoxone, Cadre/Impose, Ultra Blazer, Cobra, Storm, 2,4-DB) controlled this weed much less (essentially no control.) Note that Strongarm can be applied only through the cracking stage of peanut. So, it is important to control this weed with burndown programs.
We have even had his weed be an issue in conventional tillage (which is somewhat surprising but certainly not out of the question.) A key, whether in reduced tillage or conventional tillage, is to control it with burndown sprays. Adequate rates of glyphosate and paraquat and use of auxin herbicides earlier in the season are important in controlling dogfennel. But, we may be experiencing some gaps when we apply burndowns early and get emergence after those sprays and before (and even after) peanuts are planted. We just don’t have effective tools after peanuts emerge. Look closely and spend the extra money if needed before peanuts come up.
Dr. Charlie Cahoon (cotton and corn weed scientist at NC State University) and I plan to look into this more in the future. This has become a nagging and important question over the past few years, especially in the northern peanut belt of North Carolina and in Virginia.