Problem Weed Control in Glyphosate-Resistant Soybean with Glyphosate Tank Mixes and Soil-Applied Herbicides

Abstract

Although glyphosate controls many plant species, certain broadleaf weeds in Nebraska's cropping systems exhibit various levels of tolerance to the labeled rates of this herbicide, including ivyleaf morningglory, Venice mallow, yellow sweetclover, common lambsquarters, velvetleaf, kochia, Russian thistle, and field bindweed. Therefore, two field studies were conducted in 2004 and 2005 at Concord and North Platte, NE, to evaluate performance of (1) seven preemergence (PRE) herbicides and (2) glyphosate tank mixes applied postemergence (POST) at three application times for control of eight weed species that are perceived as problem weeds in glyphosate-resistant soybean in Nebraska. The PRE herbicides, including sulfentrazone plus chlorimuron, pendimethalin plus imazethapyr, imazaquin, and pendimethalin plus imazethapyr plus imazaquin provided more than 85% control of most weed species tested in this study 28 d after treatment (DAT). However, sulfentrazone plus chlorimuron and pendimethalin plus imazethapyr plus imazaquin were the only PRE treatments that provided more than 80% control of most weed species 60 DAT. In the POST glyphosate tank-mix study, the level of weed control was significantly affected by the timing of herbicide application; control generally decreased as weed height increased. In general, glyphosate tank mixes applied at the first two application times (early or mid-POST) with half label rates of lactofen, imazamox, imazethapyr, fomesafen, imazaquin, or acifluorfen, provided more than 80% control of all species that were 20 to 30 cm tall except ivyleaf morningglory, Venice mallow, yellow sweetclover, and field bindweed. Glyphosate tank mixes applied late POST with lactofen, imazethapyr, or imazaquin provided more than 70% control of common lambsquarters, velvetleaf, kochia, and Russian thistle that were 30 to 50 cm tall. Overall, glyphosate tank mixes with half label rates of chlorimuron or acifluorfen were the best treatments; they provided more than 80% control of all the studied weed species when applied at early growth stages. Results of this study suggested that mixing glyphosate with other POST broadleaf herbicides, or utilizing soil-applied herbicides after crop planting helped effectively control most problematic weeds in glyphosate-resistant soybean in Nebraska.

Delay in the critical time for weed removal in imidazolinone-resistant sunflower (Helianthus annuus) caused by application of pre-emergence herbicide

“…Although the regression lines appear similar at some locations (e.g. at Surduk in 2008and 2009, Zemun Polje in 2008and Radmilovac in 2009, the lines are different from each other based on the regression parameters (Figure 1a, b; Table 2). In general, sunflower yields varied between years and among locations.…”

“…Even though the use of HRCs may have advantages over conventional herbicide programmes, there are risks associated with their use which include herbicide drift, misapplication, weed resistance, weed population shifts and HRC volunteer plants in subsequent crops (Sikkema et al 1999;Knezevic et al 2003Knezevic et al , 2009). The cropping systems utilizing HRCs need to include the fundamental components of integrated weed management (IWM) systems such as knowledge of the critical period for weed control (CPWC) (Van Acker et al 1993;Knezevic et al 2002Knezevic et al , 2003, which can provide guidelines for a well-timed use of low-or non-residual POST herbicides (Knezevic et al 2002(Knezevic et al , 2003.…”

Weed Control in Soybean with Preemergence‐ and Postemergence‐applied Herbicides

“…Results showed the effective broad‐spectrum weed control when premixes from Group 2 (ALS‐inhibitors), Group 5 (Photosystem II [PSII]‐inhibitors), Group 14 (protoporphyrinogen oxidase [PPO]‐inhibitors), and Group 15 (long‐chain fatty acid‐inhibitors) herbicides. Similarly, others reported that PRE application of PPO herbicides tank‐mixed with ALS‐inhibiting herbicides provided an effective control of broadleaf species (Belfry et al, 2015; Walsh et al, 2015); including kochia, Russian thistle ( Salsola tragus ), field bindweed ( Convolvulus arvensis ), velvetleaf, common lambsquarters, and yellow sweetclover ( Melilotus officinalis ) in Nebraska (Knezevic et al, 2009). Hausman et al (2013) also reported that PRE‐applied metribuzin and flumioxazin alone provided 92% waterhemp control at 60 DAPRE in soybean.…”

Comparisons of Genetically Modified and Non‐Genetically Modified Soybean Cultivars and Weed Management Systems

“…Weed management decisions must address the primary premise of herbicide use, which is to protect the crop from losses attributable to weed interference, and include decisions refl ecting choices of tillage, herbicide application timing, types of herbicides, time of weed removal, herbicide rate, row spacing, plant population density, and other factors (Beyers et al, 2002;Cox et al, 2006;Culpepper et al, 2000;Dalley et al, 2004a, b;Knezevic et al, 2002Knezevic et al, , 2003Knezevic et al, , 2009Wait et al, 1999). Weed management decisions must address the primary premise of herbicide use, which is to protect the crop from losses attributable to weed interference, and include decisions refl ecting choices of tillage, herbicide application timing, types of herbicides, time of weed removal, herbicide rate, row spacing, plant population density, and other factors (Beyers et al, 2002;Cox et al, 2006;Culpepper et al, 2000;Dalley et al, 2004a, b;Knezevic et al, 2002Knezevic et al, , 2003Knezevic et al, , 2009Wait et al, 1999).…”