Preemergent Control of Medusahead on California Annual Rangelands With Aminopyralid

Abstract

Medusahead (Taeniatherum caput-medusae [L.] Nevski), the most problematic invasive grass on many California rangelands, is difficult to control selectively in grasslands. Prescribed burning, grazing, and herbicides have been tested with some success but are not practical in all situations. The selective herbicide aminopyralid, normally used for control of certain broadleaf species such as thistles, suppresses some annual grasses when applied pre-or early postemergence. In 2009-2010, we tested the efficacy of aminopyralid for medusahead control in preemergence applications at three foothill rangeland sites in northern California. We compared a rate series of aminopyralid (53, 88, 123, and 245 g Á ha À1 acid equivalent [ae]) with rimsulfuron (18 and 35 g Á ha À1 active ingredient) and imazapic (140 g Á ha À1 ae). Plots were 339 m with four replications at each site. Treatments were applied in early fall 2009. In May 2010, we took visual cover estimates and biomass/seedhead samples in three quadrats per plot. In regression analysis, medusahead cover was found to decrease consistently with increasing rates of aminopyralid. Medusahead control at the highest rates of aminopyralid was consistent across the three sites, averaging 89% 6 3 standard deviation (SD) with 245 g Á ha À1 ae and 59% 6 10 SD with 123 g Á ha À1 ae. Aminopyralid at lower rates, rimsulfuron, and imazapic were less consistent. Cover of other annual grasses increased in plots treated with aminopyralid at all sites. Aminopyralid has potential utility for suppressing medusahead, particularly in sites also infested with invasive members of the Asteraceae. However, the most effective rate (245 g Á ha À1 ae) is registered for use only as a spot application. In situations where this rate can be justifiably used, it would be expected to give season-long control of medusahead, as well as longer-term control of thistles and other susceptible species. Resumen Medusahead (Taeniatherum caput-medusae [L.] Nevski), la especie de pasto invasiva má s problemá tica en muchas á reas de California, es difícil de controlar selectivamente en los pastizales. Se ha probado el fuego prescrito, el pastoreo, y los herbicidas con algo deéxito pero no son prá cticos en todas las situaciones. El herbicida selectivo aminopyralid, normalmente usado para el control de ciertas especies de hoja ancha como cardo, suprime algunos pastos anuales cuando se aplica durante la etapa de pre o al inicio de pos-emergencia. In 2009-2010 se evaluó la eficiencia de aminopyralid para controlar medusahead en aplicaciones pre-emergentes en tres sitios localizados en pastizales del norte de California. Se compararon una serie de rangos de aplicación de aminopyralid (53, 88, 123, y 245 g Á ha À1 acido equivalente [ae]) con rimsulfuron (18 y 35 g Á ha À1 de ingrediente activo) e imazapic (140 g Á ha À1 ae). Las parcelas fueron de 3 m por 9 m con cuatro repeticiones en cada sitio. Los tratamientos se aplicaron durante el inicio del verano de 2009. En mayo de 2010 se tomo una estimación visual de la cobert...

Efficacy of the Herbicide Lancelot 450 WG (Aminopyralid + Florasulam) on Broadleaf and Invasive Weeds and Effects on Yield and Quality Parameters of Maize

“…The above mentioned species were the dominant weeds in the specific field and consequently their long-term control is considered crucial for crop's performance. This residual efficacy of similar mixtures has been previously shown [16], while the need of herbicides with long-term activity against weeds was indicated [14,19]. The only case of higher efficacy of the high compared with the low dose of Lancelot 450 WG was against the noxious C. arvense at 28 DAT.…”

“…Even if it is normally used for control of certain broadleaf species such as thistles, it also suppresses some annual grasses when applied pre-or early post-emergence [13]. Aminopyralid has potential utility for suppressing several weeds and reducing their seed bank, particularly in sites also infested with invasive members of the Asteraceae [14]. It has been reported that aminopyralid residues in soil affect crop rotation, with maize appearing to be the best option for land recently used with aminopyralid [15].…”

Timing Aminopyralid to Prevent Seed Production Controls Medusahead (Taeniatherum caput-medusae) and Increases Forage Grasses

“…Compared with the current approach of applying aminopyralid in fall (Kyser et al 2012b;Miller et al 2014), applying it in spring provided better control of T. caput-medusae. The data indicate this in two ways.…”

“…However, glyphosate provided only 61% control in one experiment (Kyser et al 2013b), and it is not clear that glyphosate applications could be timed to control T. caput-medusae without damaging annual forage grasses in our study system. Like glyphosate, imazapic can provide excellent control of T. caput-medusae (Davies and Sheley 2011;Jeffries et al 2016;Kyser et al 2007;Sheley et al 2007Sheley et al , 2012aSheley et al , 2012b; but see Kyser et al 2012b;Monaco et al 2005), but this herbicide poses serious risks to annual forage grasses (Jeffries et al 2016;Kyser et al 2007). Two other herbicides, rimsulfuron and sulfometuron methyl, have provided inconsistent control of T. caput-medusae (Kyser et al 2012b(Kyser et al , 2013bMiller et al 2014;Monaco et al 2005).…”

Magnetic molecularly imprinted polymers for the detection of aminopyralid in milk using dispersive solid-phase extraction

“…1 Aminopyralid exerts highly efficient and selective weed removal since it can be quickly absorbed by the stems and leaves of plants and interrupt plant growth, causing rapid death. 2,3 Despite its low toxicity and high herbicidal activity, concerns have been raised 4 because its improper use may cause negative impacts on human health. Research has shown that aminopyralid taken up by livestock through animal feed causes irreversible damage to human kidneys, because it exists as an exogenous anti-nutritional factor in the animal-derived foods.…”