Herbicide Systems for Control of Horse Purslane (Trianthema portulacastrum L.), Smellmelon (Cucumis melo L.), and Palmer Amaranth (Amaranthus palmeri S. Wats) in Peanut

Abstract

Field studies were conducted during the 2003 through 2005 growing seasons to evaluate soilapplied herbicides alone or in combination with postemergence (POST) herbicides for horse purslane, smellmelon, and Palmer amaranth control in peanut. Pendimethalin alone applied preplant incorporated (PPI) failed to control any of the three weeds (, 70% control). Pendimethalin in combination with diclosulam, followed by imazethapyr applied preemergence (PRE), or followed by either acifluorfen or imazapic applied postemergence (POST) controlled all three weed species at least 80%. The soil-applied herbicides flumioxazin, imazethapyr, S-metolachlor, or dimethenamid applied alone failed to control horse purslane and smellmelon (, 75%). Pendimethalin controlled Palmer amaranth less than 42% while flumioxazin at 0.07 kg/ha or dimethenamid at 1.12 kg/ha controlled Palmer amaranth less than 75%. Imazethapyr alone or pendimethalin applied PPI followed by imazethapyr applied PRE or imazapic applied POST controlled Palmer amaranth at least 99%. Pendimethalin applied PPI was present in all herbicide systems that yielded greater than the untreated check. In addition, 80% or greater control of at least 2 of 3 weed species resulted in the highest yields, with the exception of pendimethalin followed by acifluorfen.

Effect of Sequential Applications of Protoporphyrinogen Oxidase-Inhibiting Herbicides on Palmer Amaranth (Amaranthus palmeri) Control and Peanut Response

“…Also, the lactofen product label requires that sequential applications be made at least 14 DAIT, possibly because the level of control does not improve when applied at a shorter interval (Anonymous 2015). Although studies have shown lactofen to have higher activity on Palmer amaranth than acifluorfen, bentazon, or 2,4-DB, many of these studies did not investigate the recovery of Palmer amaranth over time (Grichar 1997a(Grichar , 2008Mayo et al 1995). Gaeddert et al (1997) did record Palmer amaranth control over time and found that acifluorfen and lactofen provided the same level of control 7 d after treatment, but by 28 d after treatment lactofen provided 16% more control than acifluorfen.…”

“…For mid-season application, the only other effective herbicides are the PPO-inhibitors. Palmer amaranth is adequately controlled by PPO-inhibiting herbicides when plants are less than 10 cm tall, but control declines quickly as plants surpass 10 cm in height (Gaeddert et al 1997;Grichar 2007Grichar , 2008Grichar and Dotray 2011;Mayo et al 1995;Morichetti et al 2012). If applied when plants are taller than 10 cm, most PPO-inhibiting herbicides control Palmer amaranth for 1 to 2 wk after treatment, but plants do not completely die and regrowth occurs (Morichetti et al 2012).…”

“…Consequently, 159 weed species are now resistant to ALS-inhibiting herbicides, more than are resistant to any other mode of action (Heap 2016). Palmer amaranth resistance to ALSinhibiting herbicides was first confirmed in Kansas in 1991, and later was discovered in Georgia and Florida in 2000and 2008, respectively (Heap 2016Horak and Peterson 1995). Surveys in these two states have shown that ALS-resistant Palmer amaranth has spread aggressively across peanut-growing regions.…”

Weed Control and Peanut (Arachis hypogaea L.) Cultivar Response to Encapsulated Acetochlor

“…Subsequent new growth did not show the effects of the lactofen applications and was 2% or less four wks after application (data not shown). Other studies have reported that lactofen injury is transient and subsequent growth does not show any effects of the herbicide (Grichar, 2007;2008;Grichar and Dotray, 2011). Weed Control.…”

“…Postemergence applications of imazapic, lactofen, lactofen plus S-metolachlor, or lactofen plus acetochlor included a crop oil concentrate (Agridex, Helena Chemical Co., Memphis, TN 38119) at 1% (v/v) at both locations. The pendimethalin followed by imazapic treatment was included because it is a commercial standard in many peanut growing areas of the state (Grichar 2007;2008). An non-treated check was also included at both locations.…”