For the most part, the effectiveness of common peanut herbicide applications are not influenced by time of application, research at the University of Georgia reveals.

In a paper presented to the annual meeting of the American Peanut Research and Education Society in Clearwater, Fla., Wen Carter, a graduate student in weed science working under the guidance of Extension weed science specialist Eric Prostko, shared results of the study conducted in 2015 at the University of Georgia Ponder Research Farm in Tifton.

In the research, a small plot replicated field trial was conducted in a non-crop (bare ground) scenario. Various commonly used weed control treatments were applied at 7 a.m., 12 p.m., 5 p.m. and 10 p.m. Herbicides used were paraquat, bentazon, s-metolachlor, imazapic and lactofen.

“At the time of application, Palmer amaranth was two to six inches tall, Florida beggarweeed  was one to two inches tall  and several species of annual grasses were one to three inches tall,” Carter explained.

“At 15 days after treatment, a significant interaction between time of day and treatment was observed for Palmer amaranth, Florida beggarweed, and annual grass control,” Carter noted. “Palmer amaranth control with imazapic was most effective at the 5 p.m. timing and control was not influenced by time of day with the paraquat or lactofen treatments. Florida beggarweed control was most effective with lactofen at the 7 a.m. timing and the paraquat and imazapic treatments showed no significant difference in control across the four timings.”

Carter noted that annual grass control with paraquat was reduced at 7 am when compared to the other timings. Control of annual grass with lactofen was most effective at the 7 am timing when compared to the other timings and control with imazapic was not affected by time of day.

An additional in-crop study was conducted comparing the performance of recommended peanut herbicide programs sprayed at the same four timings of 7 am, 12 pm, 5 pm, and 10 pm. Herbicides  used were parquat, aclifurofen, bentazon, s-meatachlor followed by either imazapic, s-metolachlor or lactofen.

“Treatments were applied when Palmer amaranth was two to three inches tall. There was no interaction between time of day or herbicide treatment. After the entire herbicide program was applied, neither time of day nor treatment had an influence on Palmer amaranth control. Peanut yields were not influenced by time of day or treatment,” Carter said.