Question:
I am reaching out because I have been following your extension work and advice regarding peanut production. As an agricultural economist, I am analyzing the peanut production system to understand how growers use paraquat and what the landscape for alternatives looks like, given the pressure to limit/ban its use.
Jordan:
A summary of herbicides can be found in the following post.
https://peanut.ces.ncsu.edu/news/comments-on-weed-management-peanut-grower-peanut-notes-no-70-2026/
It takes at least 4 herbicide sprays to adequately control weeds season long in peanuts. That is a minimum in most fields. Peanuts are not competitive with weeds, weeds remaining in the field can cause greater yield loss when pods are dug and vines inverted, and weeds interfere with fungicide deposition and subsequent disease control. Most growers apply flumioxazin plus S-metolachlor right after planting. Then, a significant number of growers apply paraquat plus bentazon at some point as peanuts emerge up to 28 days after peanuts emerge. On many occasions, a Group 15 herbicide is added for residual control. Other herbicides can be applied in this window and later. I can point you to that information on the NC State Extension portal. The Group 15 herbicides only control weeds that have not emerged. A contact herbicide that controls the emerged weeds is needed in the mixture with the Group 15 residual herbicides. This is where paraquat plays a significant role.
Paraquat is broad spectrum and relatively inexpensive. But beyond that, it has a site of action different from all other contact and residual herbicides used in peanuts. We have documented cases of PPO resistance (lactofen, acifluorfen, flumioxazin, carfentrazone) and ALS resistance (imazapic, diclosulam, imazethapyr) in some fields in NC to various degrees. There is no documented resistance of key weeds in peanuts to paraquat. Therefore, the value of paraquat for resistance management cannot be overestimated.
Can we control weeds in peanuts without paraquat? Yes, in some fields. But in other fields not very well. What happens if it is not used? We select for evolved resistance to the herbicides mentioned above much more rapidly. It is cost effective in the peanut crop and very important for resistance management. Paraquat is extending the life and usefulness of many of our current peanut herbicides.
For a survey of herbicide use patterns in NC and surrounding states, search for the following article.
Jordan, D.L., D. Anco, M. Balota D. Langston, L. Lux, B. Shew, and R. Brandenburg. 2024. Survey of herbicide and fungicide use in peanut in North Carolina and Virginia in the United States. Crop, Forage, and Turfgrass Management, 10, e20272. 20263. https://doi.org/10.1002/cft2.20263.