Phytotoxicity of Delayed Applications of Dinitroaniline Herbicides in Strip-Tillage Peanut Production

Abstract

Dinitroaniline herbicides are typically applied preplant incorporated or preemergence (PRE) immediately after seeding peanut. Situations frequently arise where dinitroaniline herbicides are not applied in a timely manner in strip-tillage peanut production. In these cases, dinitroaniline herbicides are be applied several days or weeks after seeding peanut. Weed-free, irrigated field trials were conducted in Tifton, GA in 2004 and2005 to evaluate the phytotoxic effects of delayed applications of ethalfluralin and pendimethalin on peanut. Both herbicides were applied PRE, at vegetative emergence (VE), 1wk after vegetative emergence (VE+1wk), VE+2wk, VE+3wk, VE+4wk, and included a nontreated control. Dinitroaniline herbicides neither visually injured peanut nor affected foliage biomass collected at mid-and late-season. Timing of herbicide application did not consistently affect peanut vegetative growth. Pod biomass was reduced by dinitroaniline herbicides applied VE+3wk when measured mid-season, but recovered late-season. Across all application timings, ethalfluralin reduced peanut yield compared to pendimethalin. Across both dinitroaniline herbicides, peanut yields were reduced when herbicides were applied at VE. These data show that visual estimates of peanut response to dinitroaniline herbicides may not detect subtle phytotoxic effects. The data also suggests that pod biomass and yield responses may be difficult to predict. However, there is potential for significant injury if peanut are treated with delayed applications of dinitroaniline herbicides in strip-tillage peanut production. In contrast, PRE applications are not injurious to strip-tillage peanut and must be a priority to ensure crop safety.

A systematic review of chemical weed management in peanut (Arachis hypogaea) in the United States: challenges and opportunities

“…Peanut injury, expressed as stunting, swollen hypocotyls, and abnormal lateral root growth, has been observed with dinitroaniline herbicides (Johnson et al 1997; Johnson and Mullinix 1999). The level of injury from these herbicides can vary depending on the method, timing, and rates of application (Johnson and Mullinix 1999; Johnson et al 2011). Ethalfluralin and pendimethalin were reported to be more injurious to peanut when applied preplant incorporated than preemergence, and injury increased with increasing rate of application from 0.6 to 2.2 kg ai ha −1 for each herbicide (Johnson and Mullinix 1999).…”

“…Ethalfluralin and pendimethalin were reported to be more injurious to peanut when applied preplant incorporated than preemergence, and injury increased with increasing rate of application from 0.6 to 2.2 kg ai ha −1 for each herbicide (Johnson and Mullinix 1999). Similarly, applications of ethalfluralin and pendimethalin delayed until 3 wk after emergence caused significant injury and reduced peanut yield compared with preemergence applications (Johnson et al 2011). Dinitroaniline injury can also be undetected until harvest, because the vegetative growth may appear unaffected, but injured plants often have large numbers of pegs and very few pods (Johnson et al 2011).…”

“…Similarly, applications of ethalfluralin and pendimethalin delayed until 3 wk after emergence caused significant injury and reduced peanut yield compared with preemergence applications (Johnson et al 2011). Dinitroaniline injury can also be undetected until harvest, because the vegetative growth may appear unaffected, but injured plants often have large numbers of pegs and very few pods (Johnson et al 2011). Peanut gynophores (pegs) form aboveground and grow downward to penetrate the soil surface (pegging), where they contact damaging levels of the herbicide at the soil surface.…”

“…Similarly, peanut yield was not affected by preplant-incorporated application of ethalfluralin and pendimethalin at 0.67 to 1.68 kg ai ha −1 and trifluralin at 0.56 and 0.71 kg ai ha −1 in five runner-type cultivars. However, Johnson et al (2011) showed that both ethalfluralin and pendimethalin have the potential to inhibit pod formation and reduce peanut yield in strip-tillage systems, especially when the application is delayed. Studies have also reported that cover crop debris present in strip-tillage systems can influence the availability of herbicide, which may cause the herbicide to be more injurious to peanut (Johnson et al 2002; Weber 1990).…”