The critical timing of weed removal (CTWR) is the point in crop development when weed control must be initiated to prevent crop yield loss due to weed competition. A field study was conducted in 2018 and 2020 near Scottsbluff, NE, to determine how the use of preemergence herbicides affects the CTWR in dry bean. The experiment was arranged as a split plot, with herbicide treatment and weed removal timing as main and sub-plot factors, respectively. Herbicide treatments consisted of no-preemergence application, or pendimethalin (1,070 g ai ha–1) + dimethenamid-P (790 g ai ha–1) applied preemergence. Sub-plot treatments included season-long weed-free, weed removal at: V1, V3, V6, R2, and R5 dry bean growth stages, and a season-long weedy control. A four-parameter logistic model was used to estimate the impact of time of weed removal, for all response variables including dry bean yield, dry bean plants m–1 row, number of pods per plant, number of seeds per pod, and seed weight. The CTWR based on 5% yield reduction was estimated to range from the V1 growth stage [(16 d after emergence (DAE)] to the R1 growth stage (39 DAE) in the no-preemergence herbicide treatment. In the preemergence-applied treatment, the CTWR began at the R2 growth stage (47 DAE). Number of dry bean plants m–1 row was reduced in the no-preemergence treatment when weed removal was delayed beyond the R2 growth stage in the 2020 field season. The use of preemergence herbicides prevented a reduction in the number of pods per plant in 2020, and the number of seeds per pod in 2018 and 2020. In 2018, the number of pods per plant was reduced by 73% when no preemergence herbicide was applied, compared to 26% in the preemergence-applied treatment. The use of preemergence-applied soil-active herbicides in dry bean delayed the CTWR and preserved yield potential.

Late-emerging summer annual weeds are difficult to control in dry bean production fields. Dry bean is a poor competitor with weeds, due to its slow rate of growth and delayed canopy formation. Palmer amaranth is particularly difficult to control due to season-long emergence and resistance to acetolactate synthase (ALS)-inhibiting herbicides. Dry bean growers rely on PPI and preemergence residual herbicides for the foundation of their weed control programs; however, postemergence herbicides are often needed for season-long weed control. The objective of this experiment was to evaluate effect of planting date and herbicide program on late-season weed control in dry bean in western Nebraska. Field experiments were conducted in 2017 and 2018 near Scottsbluff, NE. The experiment was arranged in a split-plot design, with planting date and herbicide program as main-plot and subplot factors, respectively. Delayed planting was represented by a delay of 15 d after standard planting time. The treatments EPTC + ethalfluralin, EPTC + ethalfluralin followed by (fb) imazamox + bentazon, and pendimethalin + dimethenamid-P fb imazamox + bentazon, resulted in the lowest Palmer amaranth density at 3 wk after treatment and the highest dry bean yield. The imazamox + bentazon treatment provided poor Palmer amaranth control and did not consistently result in Palmer amaranth density and biomass reduction compared with the nontreated control. In 2018, the delayed planting treatment had reduced Palmer amaranth biomass with the pendimethalin + dimethenamid-P treatment, as compared with standard planting. Delaying planting did not reduce dry bean yield and had limited benefit in improving weed control in dry bean.

Field studies were conducted from 2009 through 2011 at the Sustainable Agriculture Research and Extension Center near Lingle, Wyoming, to evaluate great northern bean response to PRE flumioxazin mixed with either trifluralin, pendimethalin, or ethalfluralin. Seven treatments were arranged in a randomized complete block with three or four replicates y−1. The soil texture of the study site was loam in 2009 and 2011, and sandy loam in 2010. Soil organic matter ranged from 1.4% to 1.8%. Treatments included flumioxazin plus trifluralin, flumioxazin plus pendimethalin, flumioxazin plus ethalfluralin, ethalfluralin plus EPTC, imazamox plus bentazon (POST), hand-weeded control, and nontreated control. Dry bean density 4 wk after planting differed among herbicide treatments (P < 0.001). Treatments that included flumioxazin reduced dry bean density 54% compared with treatments without flumioxazin. Dry bean yield was influenced by dry bean density; on average, yield in flumioxazin-containing herbicide treatments was 30% less than treatments not containing flumioxazin, even though weed control was generally greater in flumioxazin treatments.

The occurrence of herbicide tank contamination with dicamba or 2,4-D will likely increase with the recent commercialization of dicamba- and 2,4-D-resistant soybean. High-value sensitive crops, including dry bean, will be at higher risks for exposure. In 2017 and 2018, two separate field experiments were conducted in Michigan to understand how multiple factors may influence dry bean response to dicamba and 2,4-D herbicides, including 1) the interaction between herbicides applied POST to dry bean and dicamba or 2,4-D, and 2) the impact of low rates of glyphosate with dicamba or 2,4-D. Dry bean injury was 20% and 2% from POST applications of dicamba (5.6 h ae ha−1) and 2,4-D (11.2 g ae ha−1), respectively, 14 days after treatment (DAT). The addition of glyphosate (8.4 g ae ha−1) did not increase dry bean injury from dicamba or 2,4-D. Over 2 site-years the addition of dry bean herbicides to dicamba or dicamba + glyphosate (8.4 g ae ha−1) increased dry bean injury and reduced yield by 6% to 10% more than when dicamba or dicamba + glyphosate was applied alone. The interaction between 2,4-D (11.2 g ae ha−1) and dry bean herbicides was determined to be synergistic. However, 2,4-D (11.2 g ae ha−1) had little effect on dry bean with or without the addition of a dry bean herbicide program. These studies document that synergy also occurs between dicamba and dicamba + glyphosate and both common dry bean herbicide programs tested: 1) imazamox (35 g ha−1) + bentazon (560 g ha−1), and 2) fomesafen (280 g ha−1). The synergy between dry bean herbicide and dicamba and dicamba + glyphosate can increase plant injury, delay maturity, and reduce yield to a greater extent than dicamba or dicamba + glyphosate alone. This work emphasizes the need to properly clean out sprayers after applications of dicamba to reduce the risk of exposure to other crops.

Dicamba and 2,4-D exposure to sensitive crops, such as dry bean, is of great concern with the recent registrations of dicamba- and 2,4-D–resistant soybean. In 2017 and 2018, field experiments were conducted at two Michigan locations to understand how multiple factors, including dry bean market class, herbicide rate, and application timing, influence dry bean response to dicamba and 2,4-D. Dicamba and 2,4-D at rates of 0.1%, 1%, and 10% of the field use rate for dicamba and 2,4-D choline were applied to V2 and V8 black and navy bean. Field-use rates for dicamba and 2,4-D choline were 560 and 1,120 g ae ha−1, respectively. There were few differences between market classes or application timings when dry bean was exposed to dicamba or 2,4-D. Estimated rates to cause 20% dry bean injury 14 d after treatment were 4.5 and 107.5 g ae ha−1 for dicamba and 2,4-D, respectively. When dicamba was applied at 56 g ae ha−1, light interception was reduced up to 51% and maturity was delayed up to 16 d. Although both herbicides caused high levels of injury to dry bean, yield reductions were not consistently observed. At four site-years, 2,4-D did not reduce dry bean yield or seed weight with any rate tested. However, when averaged over site-years, dicamba rates of 3.7, 9.8 and 17.9 g ae ha−1 were estimated to cause 5%, 10%, and 15% yield loss, respectively. Dicamba also reduced seed weight by 10% when 56 g ae ha−1 was applied. However, the germination of harvested seed was not affected by dicamba or 2,4-D. Long delays in dry bean maturity from dicamba injury can also indirectly increase losses in yield and quality due to harvestability issues. This work further stresses the need for caution when using dicamba or 2,4-D herbicides near sensitive crops.

White mold caused by the fungus, Sclerotinia sclerotiorum is a devastating disease of soybean (Glycine max) and other leguminous crops, including dry bean (Phaseolus vulgaris). Previous research has demonstrated that no-till planting soybean into rolled–crimped cereal rye residue can enhance weed management, improve soil health and reduce labor requirements in organic production. However, there are limited data on the effects of cereal rye residue on white mold suppression in no-till planted soybean and dry bean. Two field trials were conducted in 2016–2017 (Year 1) and repeated in 2017–2018 (Year 2) to evaluate the potential of cereal rye cover crop residue to suppress white mold in these crops. In each trial (soybean and dry bean), the experimental design was a randomized complete block with two treatments: (1) rolled–crimped cereal rye residue and (2) no cover crop control. Treatment effects on plant population, biomass and yield components varied between the main crops. Compared with the control treatment, cereal rye residue reduced the incidence of white mold in soybean in both years and in dry bean in Year 2. The reduction in white mold in cereal rye residue plots was due to a combination of (1) decreased sclerotial germination (no stipes formed) and (2) increased nonfunctional sclerotial germination defined here as sclerotia that germinated but produced stipes without the expanded cup where asci containing ascospores are formed. Weed density and biomass were lower in cereal rye residue plots in soybean and dry bean, except in Year 1 in soybean when weed biomass was low in both treatments. Our findings indicate that cereal rye residue could help organic and conventional farmers manage white mold in no-till planted soybean and dry bean. Germination of sclerotia resulting in nonfunctional apothecia could potentially exhaust soilborne inoculum in the upper soil profile and reduce infections in subsequent crops.

Earlier reports have summarized crop yield losses throughout various North American regions if weeds were left uncontrolled. Offered here is a report from the current WSSA Weed Loss Committee on potential yield losses due to weeds based on data collected from various regions of the United States and Canada. Dry bean yield loss estimates were made by comparing dry bean yield in the weedy control with plots that had >95% weed control from research studies conducted in dry bean growing regions of the United States and Canada over a 10-year period (2007 to 2016). Results from these field studies showed that dry bean growers in Idaho, Michigan, Montana, Nebraska, North Dakota, South Dakota, Wyoming, Ontario, and Manitoba would potentially lose an average of 50%, 31%, 36%, 59%, 94%, 31%, 71%, 56%, and 71% of their dry bean yield, respectively. This equates to a monetary loss of US $36, 40, 6, 56, 421, 2, 18, 44, and 44 million, respectively, if the best agronomic practices are used without any weed management tactics. Based on 2016 census data, at an average yield loss of 71.4% for North America due to uncontrolled weeds, dry bean production in the United States and Canada would be reduced by 941,000,000 and 184,000,000 kg, valued at approximately US $622 and US $100 million, respectively. This study documents the dramatic yield and monetary losses in dry beans due to weed interference and the importance of continued funding for weed management research to minimize dry bean yield losses.

Dry bean (Phaseolus vulgaris) can be grown as a local food source and as an alternative to soybean (Glycine max) to diversify organic crop rotations. To understand the benefits of diversification of organic cropping systems, the effects of preceding alfalfa (Medicago sativa) and corn (Zea mays) crops on yields of five dry bean types and one soybean type, and the effect of bean type on following spring wheat (Triticum aestivum) yields, were tested at four Minnesota locations. Dry bean and soybean yields following alfalfa were 25% greater than yields following corn at two of four locations, though bean yields following corn were greater at one location. A preceding alfalfa crop benefited bean yields at locations where hog manure or no manure was applied to corn, whereas bean yields following corn fertilized with cow manure were similar to or greater than bean yields following alfalfa. Among dry bean types, black bean yielded similarly to soybean at three of four locations, but dark red kidney bean consistently yielded 25–65% lower than soybean. Navy, pinto and heirloom dry bean types yielded similarly to soybean at two of four locations. Across locations, weed biomass was 3–15 times greater in dry bean than in soybean and dry bean yield response to weed competition varied among bean types. However, dry bean, regardless of the preceding crop, demonstrated the potential to produce yields comparable with soybean in organic systems and the substitution of dry bean for soybean did not affect subsequent wheat yields. More studies are needed to identify nitrogen fertility dynamics in organic systems as they relate to dry bean yield.

Five field trials were conducted over a 2-yr period (2007, 2008) at various locations in Ontario to evaluate the tolerance of black, cranberry, kidney, otebo, pink, pinto, small red Mexican (SRM), and white bean to halosulfuron applied PPI, PRE, and POST at 35 and 70 g ai/ha. There was minimal injury (3% or less) with halosulfuron applied PPI or PRE in dry bean. At Exeter and Ridgetown, halosulfuron applied POST at 35 and 70 g/ha caused 3 to 5% and 4 to 8% injury in dry bean, respectively at 1 wk after herbicide application (WAA). The injury was transient with no significant injury at 2 and 4 WAA. At Harrow, halosulfuron POST at 35 and 70 g/ha caused as much as 4% injury at 35 g/ha and 14% injury at 70 g/ha in dry bean. Halosulfuron applied PPI, PRE, and POST at 35 and 70 g/ha caused no decrease in plant height of dry bean except for kidney bean, which was reduced 6% at 70 g/ha, and white bean, which was reduced 3% at both 35 and 70 g/ha. Halosulfuron applied PPI, PRE, and POST at 35 and 70 g/ha caused no decrease in dry bean yield except for kidney bean, which was reduced 9% at 35 g/ha and 10% at 70 g/ha; otebo bean, which was reduced 3% at 70 g/ha; and white bean, which was reduced 7% at both 35 and 70 g/ha. On the basis of these results, there is an adequate margin of crop safety in dry bean to halosulfuron applied PPI or PRE at 35 and 70 g/ha. In addition, there is an adequate margin of crop safety in black, cranberry, pink, pinto, and SRM bean to halosulfuron applied POST at 35 and 70 g/ha. However, further research is required to ascertain the tolerance of kidney, otebo, and white bean to halosulfuron applied POST.

Dry edible bean class and cultivar response to dimethenamid and metolachlor was investigated in the greenhouse and field. Kidney and cranberry cultivars, as well as a small red cultivar, were not injured by dimethenamid applied PRE at 2,100 g ai/ha in the greenhouse, whereas pinto bean tolerance varied and navy and black bean cultivars were injured by this rate. Injury to navy bean was greater in the greenhouse when dimethenamid and metolachlor were placed in the zone above and including the seed, compared with placement in the seed, root, or root plus seed zone. In an application timing field study, dimethenamid at 1,300 g/ha applied at the crook or unifoliate growth stage caused injury to navy bean, delayed maturity, and reduced seed yield. Metolachlor at 1,400 g ai/ha delayed maturity when applied at the unifoliate growth stage but did not reduce seed yield. Dimethenamid or metolachlor PRE, at 1,300 or 2,800 g ai/ha, respectively, injured navy and black bean cultivars, but seed yield was not reduced in a cultivar tolerance field study. In a planting date study, dimethenamid PRE at 2,300 g/ha reduced leaf area and delayed maturity compared with the nontreated control when pooled over five planting dates and cultivars in each of 2 yr. Metolachlor PRE at 2,800 g/ha reduced leaf area in 1 yr and delayed maturity in both years when pooled over planting dates and cultivars. If weed control and herbicide costs are comparable, metolachlor at a standard use rate is a safer choice than dimethenamid for use in navy and black bean production.

Four field trials were conducted over a 2-yr period at Exeter (2005, 2006), Harrow (2006) and Ridgetown (2006), Ontario to evaluate the tolerance of pinto and small red Mexican (SRM) bean to the POST application of bentazon, imazethapyr, or their combination. Bentazon applied once or twice (to simulate a spray overlap in the field) at 840 g ai/ha and imazethapyr applied at 37.5 g/ha caused minimal injury (6% or less) in pinto and SRM bean and had no adverse effect on plant height, shoot dry weight, seed moisture content, and yield. Imazethapyr applied twice at 37.5 and all single and repeat applications containing 75 or 150 g/ha caused 15 to 44% injury to dry bean. These injuries were persistent and reduced plant height by as much as 21% and shoot dry weight by as much as 34%, but caused no adverse effect on maturity and yield, except for imazethapyr applied twice at 150 g/ha, which delayed maturity and reduced yield 16%. The addition of bentazon to imazethapyr applied as a tankmix reduced injury by as much as 23%. Imazethapyr at 37.5 or 75 g/ha combined with bentazon at 840 g/ha applied once or twice caused 3 to 23% injury but had no adverse effect on plant height, shoot dry weight, maturity, or yield. Two applications of imazethapyr at 150 g/ha plus bentazon at 840 g/ha reduced plant height 16% and shoot dry weight 28%.

Guar production in the United States is limited to a relatively small region in the semiarid southern Great Plains of Texas and Oklahoma. The lack of POST broadleaf herbicides is a potential limiting factor to increased production. A greenhouse study was initiated in 2001 at the Texas A&M Research Center near Vernon, TX to evaluate guar tolerance to 10 POST herbicides typically used in soybean or cotton. Guar seedlings were grown in pots, and herbicides with appropriate adjuvants were applied to 3-wk-old seedlings at the registered rate (1×) and twice (2×) the registered rate for soybean or cotton. The study was repeated twice, with six replications in each run. Twenty-eight d after treatment (DAT), visual injury and aboveground dry weight of viable biomass were recorded for each plant. Significant differences (P = 0.05) were noted among herbicides for visual injury and viable biomass. Little or no differences in visual injury and aboveground dry weight were observed between the control (no herbicide applied) and the 1× rate of 4-(2,4-dichlorophenoxy)butanoic acid, bentazon, or imazethapyr 28 DAT. A 1× application rate of acifluorfen, imazamox, thifensulfuron, or bromoxynil caused minor visual injury of 7 to 9% and a reduction in dry weight of 8 to 23%. Pyrithiobac and chlorimuron caused 38 and 47% visible injury and a 35 and 58% reduction in dry weight, respectively. Guar was most sensitive to lactofen, with the 1× rate causing 100% visual injury and no recoverable aboveground biomass. This greenhouse study identified three POST herbicide candidates with potential to control broadleaf weeds in guar without noticeable plant injury, and offers data to support herbicide registrations for this minor crop.

White bean tolerance and weed control were examined by applying halosulfuron alone or in combination with pendimethalin, dimethenamid-P, or S-metolachlor applied PRE. All herbicides applied alone or in combination caused less than 3% visible injury 1 and 4 wk after emergence (WAE). Halosulfuron applied PRE provided greater than 95% control of common lambsquarters, wild mustard, redroot pigweed, and common ragweed and less than 55% control of green foxtail at 4 and 8 WAE. Weed density and dry weight at 8 WAE paralleled the control ratings. Dry bean yields in halosulfuron plus a soil applied grass herbicide did not differ compared to the weed-free control. Green foxtail competition with halosulfuron PRE applied alone resulted in reduced white bean yield compared to the weed-free control.