Time of day can impact spray: PPO herbicides more effective when sprayed at midday

February 22, 2016
New research shows that PPO herbicides applied to glyphosate-resistant weeds like Palmer amaranth, exhibit better control when applied at midday compared to early morning or early evening applications. Determining the optimal time of day to apply herbicides has long-term implications for weed management. Credit: Larry Steckel, UTIA

Some herbicides are more effective when applied at noon compared to early morning or late evening applications, according to data from the University of Tennessee Institute of Agriculture.

The study evaluated three protoporphyrinogen oxidase (PPO) herbicides applied to glyphosate-resistant Palmer amaranth in soybean plots at sunrise, noon and sunset. After 14 days, the noon applications on average performed 15-20 percent better than the sunrise applications. The noon applications outperformed the sunset applications by an average of approximately 10 percent.

"We're definitely getting better control when these herbicides are applied in the middle part of the day," says Garret Montgomery, lead author and doctoral student with UT's Department of Plant Sciences.

PPO herbicides work by inhibiting an enzyme involved in chlorophyll production. Researchers explain that this family of herbicides is significant to agricultural producers as it's the only post-emergence mode of action available for controlling glyphosate-resistant weeds in glyphosate-tolerant soybeans. Soybeans are Tennessee's top crop.

The study's findings were consistent with earlier research performed by UTIA and other universities on herbicides with different modes of action, like glufosinate. In these earlier studies, tested herbicides were also most effective when applied at midday.

The video will load shortly
Using time lapse photography, this video shows the different levels of control of glyhposate-resistant Palmer amaranth achieved by three PPO herbicides applied at sunrise, noon and sunset. Credit: Ginger Rowsey, UTIA

"Being able to determine the optimal time of day to apply herbicides is important for several reasons," says Larry Steckel, row crop weed specialist with UTIA. "Perhaps most significantly, it can reduce the number of times farmers must apply these herbicides as they work to produce a crop. Weeds that are injured but not killed from a previous application will only get more difficult and expensive to remove."

"Using our as efficiently as possible could actually reduce the rate at which weeds evolve herbicide resistance," Steckel continues. "So this study has long-term implications for weed management."

The study was conducted at the West Tennessee AgResearch and Education Center in Jackson, Tennessee, as well as the Delta Research and Extension Center in Stoneville, Mississippi.

Montgomery presented the study February 9 at the Weed Science Society of America and Southern Weed Science Society annual meeting in San Juan, Puerto Rico. The paper is titled "Environmental Influences and Time of Day Effects on PPO-Inhibiting Herbicides." Additional co-authors were Steckel along with B.H. Lawrence, H.M. Edwards and J.A. Bond of Mississippi State University. The study was supported by the United Soybean Board, Cotton Incorporated and the National Association of Conservation Districts.

Through its mission of research, teaching and extension, the University of Tennessee Institute of Agriculture touches lives and provides Real. Life. Solutions. ag.tennessee.edu

Montgomery presented the study February 9 at the Weed Science Society of America and Southern Weed Science Society annual meeting in San Juan, Puerto Rico. The paper is titled "Environmental Influences and Time of Day Effects on PPO-Inhibiting Herbicides."

Explore further: One step closer to commercial edamame production in the US

Related Stories

One step closer to commercial edamame production in the US

February 4, 2016

Edamame, touted as a healthy snack for its high protein content, is becoming increasingly popular in the United States. The soybean seeds are consumed at an immature stage, giving a sweet and slightly nutty flavor. Yet, despite ...

Old herbicides enlisted in new 'war on the weeds'

May 23, 2012

The emergence of weeds resistant to the most widely used herbicide is fostering a new arms race in the war against these menaces, which cost society billions of dollars annually in control measures and lost agricultural production. ...

Which direction are herbicides heading?

October 11, 2011

2,4-D is coming back. What many might consider a "dinosaur" may be the best solution for growers fighting weed resistance today, said Dean Riechers, University of Illinois associate professor of weed physiology.

Recommended for you

New studies take a second look at coral bleaching culprit

December 7, 2016

Scientists have called superoxide out as the main culprit behind coral bleaching: The idea is that as this toxin build up inside coral cells, the corals fight back by ejecting the tiny energy- and color-producing algae living ...

Cosmic dust found in city rooftop gutters

December 7, 2016

(Phys.org)—A small team of researchers with Imperial College London, the Natural History Museum in London, Project Stardust in Norway and Université Libre de Bruxelles in Belgium, has found samples of cosmic dust in the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.