Precipitation Influences Pre- and Post-Emergence Herbicide Efficacy in Corn

Abstract

Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum. Weather conditions before and after herbicide application can further complicate decisions because they influence herbicide efficacy. Eleven field trials were conducted at three locations in Southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST corn herbicides for weed control. The most abundant weed species across all locations were redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemisiifolia L.), common lambsquarters (Chenopodium album L.), and green foxtail (Setaria viridis (L.) Beauv.). Nine PRE herbicide treatments and eleven POST (applied at the 3 -4 leaf stage of corn) herbicide treatments were tested. Results from this study suggest that the timing and amount of precipitation influence herbicide efficacy. For example, precipitation levels 0 -17 mm within seven days after herbicide application (PRE or POST) provided unacceptable weed control in treatments that included atrazine, dimethenamid-p, isoxaflutole/atrazine or S-metolachlor/benoxacor. Cumulative precipitation during the 14 days after PRE application that exceeded the monthly average (by at least 64%) reduced Setaria viridis control with pendimethalin. This study demonstrates that a better understanding of how environmental conditions, especially precipitation affect herbicide efficacy, need to be considered by growers when selecting a corn herbicide program to reduce the possibility of weed control failure.

Influence of late emerging weeds in glyphosate-resistant corn

“…Weeds emerging after the 6th leaf stage of corn were small (low biomass/seedlings) and most likely did not reach reproductive maturity.In other studies, Stewart et al [8] found 91% -100% control of AMARE, 85% -100% of CHEAL and 78% -97% control of SETVI with a single POST application of glyphosate at 3 -4 leaf corn. Another study [20] found that ABUTH, AMARE, AM-BEL, CHEAL, and annual grasses were controlled 38% -93%, 93%, 99% -100%, 71% -100%, 30% -98% at 3 -4 leaf stage and 98% -99%, 100%, 78% -100%, 71% -98%, and 91% -100% at 7 -8 leaf stage in glyphosate resistant corn, respectively.…”

“…Glyphosate-resistant corn is popular in Eastern Canada as it provides many benefits to growers including excellent crop tolerance, a wide window of herbicide application, broad spectrum weed control, more consistent weed control under various environments, lower cost of weed control, greater yield, and higher net returns [5]. Growers often use one application of glyphosate applied early (EPOST) or late postemergence (LPOST) or a sequential application of glyphosate applied EPOST and LPOST as the primary weed management strategy to control troublesome weeds in glyphosate-resistant corn [6][7][8][9].…”

Effect of Pre and Post Emergence Herbicides to Weeds Control in Corn Field

“…Selecting a preemergence (PRE) and postemergence (POST) herbicide program that has the greatest efficacy can be difficult for corn producers and is highly dependent on weed spectrum (Stewart et al, 2012). Management of weedsis considered to be an important factor for achieving higherproductivity.…”

Comparison of Glyphosate Formulations for Weed Control and Tolerance in Maize (<i>Zea mays</i> L.) and Soybean [<i>Glycine max</i> (L.) Merr.]

“…The exceptions to this were control of pigweed species using Clearout or WiseUp and control of green foxtail using WeatherMAX or WiseUp ( Table 1). In the literature, glyphosate has been highly efficacious (e.g., greater than 90% control) on these weed species found in maize, but across years and/or locations this level of control still may not be equivalent to a weed-free control [7] [15] [16]. At 4 WAT, WeatherMAX, Clearout, and WiseUp provided equivalent control of all weed species with two exceptions: WiseUp provided better control of common ragweed than Clearout at 450 g·ae·ha −1 and WiseUp provided better control of common lambsquarters than Clearout at 225 g·ae·ha −1 .…”