Environment and Soil Conditions Influence Pre- and Postemergence Herbicide Efficacy in Soybean

Abstract

Deciding on the most efficacious PRE and POST herbicide options and their ideal application timing can be challenging for soybean producers. Climatic events during the 14 d before and after herbicide application can further complicate decisions because of their influence on herbicide effectiveness. Nine field trials were conducted at three locations in southwestern Ontario from 2003 to 2006, to determine the most effective PRE and POST soybean herbicides for control of common lambsquarters, common ragweed, green foxtail, and redroot pigweed. When precipitation was low at least 7 d before and after herbicide application weed control was reduced in treatments that included imazethapyr (PRE or POST) or flumetsulam/S-metolachlor (a premix formulation) (PRE). Cumulative precipitation during the 12 d after PRE application that exceeded the monthly average by at least 60% reduced common lambsquarters control when metribuzin was applied and green foxtail control when imazethapyr was applied. Delaying application of imazethapyr + bentazon to a later soybean growth stage decreased control of common lambsquarters and green foxtail; however, environmental conditions appeared to influence these results. Precipitation on the day of application decreased control of common ragweed and redroot pigweed more with quizalofop-p-ethyl + thifensulfuron-methyl + bentazon compared with imazethapyr + bentazon. Soybean yield varied among POST herbicide treatments because of reduced weed control. This research confirms that environmental conditions pre- and postapplication, as well as application timing, influence herbicide efficacy and should be considered by growers when selecting an herbicide program.

Influence of late emerging weeds in glyphosate-resistant corn

“…This wide range of time to control weeds to avoid yield losses necessitate glyphosate applications timings that are specific to weed populations and environmental conditions where glyphosate resistant cropping systems are being used [12]. Research has shown that a single-pass herbicide program with no residual activity can result in late emerging weeds and result in yield losses [13][14][15][16][17][18]. Other research has shown that it is possible to eliminate any yield loss due to weed interference with a single properly timed glyphosate application in glyphosate-resistant corn [19].…”

Effects of application terms of three soil active herbicides on herbicide efficacy and reproductive ability for weeds in maize

“…During 2011, the difference between PRE and EPOST application terms for this herbicide was significant (77% and 100%, respectively, probably due to low total precipitation at the time of sowing (Table 1). According to Stewart et al (2010), cumulative precipitation during the 12 days after PRE application of metribuzin that exceeded the monthly average by at least 60%, reduced C. album control. Mercurialis annua was the most tolerant weed tested; it was significantly better controlled after EPOST herbicide application (73%) compared to PRE application (32%).…”

Differences in sensitivity of F1 and F2 generations of herbicide tolerant sunflower volunteers to selected acetolactate synthase inhibiting herbicides

“…Also florasulam controlled all tested sunflower cultivars (efficacy above 85%), except for 2011 when efficacy on ExpressSun was 75% (Tables 4 and 5). Lower herbicide efficacy under dry conditions is usually caused by strongly developed protection structure (such as wax and trichomes) on leaves surface (Stewart et al 2010, Jursík et al 2011.…”