Field experiments (4 in total) were conducted in 2016 and 2017 in southwestern Ontario to compare the sensitivity of dry bean to four Group 15 herbicides applied preemergence (PRE). At 4 weeks after emergence (WAE), pethoxamid, S-metolachlor, dimethenamid- P and pyroxasulfone applied PRE at the 2X rate caused 5%, 9%, 9% and 14% visible injury in adzuki bean, 2%, 2%, 2% and 3% visible injury in kidney bean, 6%, 4%, 5% and 4% visible injury in small red Mexican (SRM) bean, and 9%, 6%, 8% and 9% visible injury in white bean, respectively. Pyroxasulfone reduced adzuki bean shoot biomass (m-1 row) 42% and height 12%. However, the other Group 15 herbicides did not reduce shoot biomass and height of adzuki bean. Kidney bean shoot biomass and height were not adversely affected by the Group 15 herbicides evaluated. S-metolachlor caused no adverse effect on SRM bean dry weight or height, but pethoxamid, dimethenamid- P and pyroxasulfone at the 2X rate reduced dry weight 26%, 28% and 28% and height 7%, 7% and 7% in SRM bean, respectively. Pethoxamid, S-metolachlor, dimethenamid- P, and pyroxasulfone applied PRE at the 2X rate reduced white bean dry weight 50%, 37%, 47% and 43% and height 16%, 10%, 16% and 15% in white bean, respectively. Pyroxasulfone (2X rate), applied PRE, reduced bean stand count and seed yield 12% and 7%, respectively. However, pethoxamid, S-metolachlor, and dimethenamid- P, applied PRE caused no decrease in stand count and seed yield of dry beans evaluated. In general, kidney and SRM bean are most tolerant, white bean is intermediate, and adzuki bean is most sensitive to Group 15 herbicides applied PRE.
Dry bean is a valuable niche market crop grown in Canada. Most of the dry bean produced in Canada is grown in Ontario and Manitoba. During 2007 to 2016, on average growers in Ontario harvested 48,455 hectares and produced 107,000 tonnes of dry bean annually, valued at US$78 million while growers in Manitoba harvested 44,608 hectares and produced 83,000 tonnes of dry bean annually, valued at US$61 million [
Group 15 herbicides include acetamide, chloroacetamide, oxyacetamide, and tetrazolinone chemical families and control susceptible weeds by impairing the formation of fatty acid biosynthesis [
Response of dry bean market classes has not been collectively compared for sensitivity to the Group 15 herbicides including pethoxamid, S-metolachlor, dimethenamid-P, and pyroxasulfone applied preemergence (PRE) under Ontario environmental conditions. Dry beans have been shown to respond differently to soil-applied herbicides [
The objective of this study was to compare the tolerance of four commonly grown market classes of dry bean in Ontario to pethoxamid at 1200 and 2400 g ai ha−1, S-metolachlor at 1600 and 3200 g ai ha−1, dimethenamid-P at 693 and 1386 g ai ha−1, and pyroxasulfone at 100 and 200 g ai ha−1, applied PRE, representing the proposed registered rate (1X) and twice that rate (2X).
Four field experiments were conducted during 2016 and 2017 at Exeter, Ontario, and Ridgetown, Ontario. The experimental design was a split plot with herbicide treatment (HERB) as the whole plot factor and dry bean type (TYPE) as the split-plot factor with four replicates. The layout was a randomized complete block design for the whole plot portion. Herbicide treatments included pethoxamid at 1200 and 2400 g ai ha−1, S-metolachlor at 1600 and 3200 g ai ha−1, dimethenamid-P at 693 and 1386 g ai ha−1, and pyroxasulfone at 100 and 200 g ai ha−1. Each plot consisted of eight rows of dry bean [two rows each of adzuki (“Erimo”), kidney (“Red Hawk”), small red Mexican (“Merlot”) and white (“T9905”) bean] spaced 0.75 m apart in rows that were 10 m long at Exeter and 8 m long at Ridgetown. Beans were planted approximately 5 cm deep at a rate of approximately 250,000 seeds ha−1.
Herbicide treatments were applied to the soil surface (not incorporated) 1 - 2 days after planting using a CO2-pressurized backpack sprayer calibrated to deliver 200 L・ha−1 at 240 kPa. The boom was 1.5 m long with four ultra-low drift ULD120-02 nozzles spaced 0.5 m apart. All experimental plots were maintained weed-free during the growing season.
Dry bean injury was evaluated visually 1, 2, 4 and 8 weeks after crop emergence (WAE) using a scale of 0 to 100%, with 0 representing no visible injury and 100% complete plant death respectively. Plant counts, shoot biomass (1 m row−1 and plant−1) were measured at 3 WAE and plant height (10 fully extended plants within each plot) was determined at 6 WAE. Dry beans were harvested from each plot with a small plot combine at maturity. Seed yields were adjusted to 14% seed moisture content for adzuki bean and 18% seed moisture content for kidney, SRM and white bean.
Data were analyzed using the GLIMMIX procedure in SAS (Ver. 9.4, SAS Institute Inc., Cary, NC) using the Laplace estimation method. The initial model was constructed based on the experimental design, and refined by comparing the most plausible random variable combinations; the final model was selected based on the best fit statistics and studentized residual plots. Fixed effects consisted of herbicide (HERB), dry bean market class (TYPE) and their interaction. Random effects included environment (location-year combinations), the environment by TYPE and environment by HERB by TYPE interactions, replication within environment and its interaction with HERB (whole plot factor). The significance of fixed and random effects was tested using the F-test and likelihood ratio tests, respectively. For each parameter analyzed, different distributions were assessed on the model scale. Once the most appropriate distribution was confirmed, least square means (LSMEANS) were calculated on the data scale using the inverse link function. Tukey’s adjustment was applied to pairwise comparisons to determine differences among treatment means at a significance level of 0.05. Percent visible injury was best described using a Poisson distribution and log link; each data point had a value of one added prior to analysis and the final LSMEANS were adjusted by subtracting a value of one. A negative binomial distribution (log link) was used for dry bean biomass per meter of row, and a gamma distribution (log link) was used for dry bean biomass per plant. Plant stand, average plant height, and dry bean yield were analyzed using a Gaussian distribution, while a lognormal distribution provided the best fit for percent moisture at harvest; the default identity link was used in both cases. Differences for main effects (HERB and TYPE) were determined only if the HERB by TYPE interaction was negligible; when the interaction was non-negligible, differences among simple effects were determined [
Visible Injury (%) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Main effectsb | 1 WAE | 2 WAE | 4 WAE | 8 WAE | Stand (# m−1) | Biomass (g・m−1) (g plant−1) | Height (cm) | Seed moisture content (%) | Yield (T ha−1) | ||
Dry bean cultivar | ** | ** | NS | ** | NS | ** | ** | ** | ** | ** | |
Adzuki | 10 c | 11 b | 6 | 2.5 b | 17.8 | 10 | 0.6 | 41 | 12.7 a | 2.20 b | |
Kidney | 2 a | 3 a | 2 | 0.5 a | 13.2 | 31 | 2.4 | 56 | 16.7 b | 2.06 b | |
Small Red Mexican | 4 ab | 6 ab | 3 | 0.7 a | 16.4 | 32 | 2.0 | 69 | 17.9 b | 3.32 a | |
White | 9 bc | 10 b | 5 | 0.8 a | 16.5 | 20 | 1.3 | 55 | 17.3 b | 3.40 a | |
Herbicide treatment | Rate (g ai ha−1) | ** | ** | ** | ** | ** | ** | ** | ** | ** | ** |
Untreated check | 0 a | 0 a | 0 | 0.0 a | 16.6 a | 26 | 1.7 | 58 | 15.5 a | 2.80 a | |
Pethoxamid | 1200 | 4 b | 5 b | 5 | 0.6 ab | 16.5 a | 23 | 1.4 | 56 | 15.9 ab | 2.81 a |
Pethoxamid | 2400 | 7 c | 9 c | 2 | 1.1 bc | 16.2 a | 19 | 1.2 | 54 | 16.6 c | 2.73 ab |
S-metolachlor | 1600 | 4 b | 5 b | 5 | 0.7 ab | 16.1 a | 24 | 1.5 | 56 | 15.8 ab | 2.72 ab |
S-metolachlor | 3200 | 7 c | 9 c | 2 | 1.0 bc | 15.5 ab | 20 | 1.3 | 55 | 16.2 bc | 2.73 ab |
Dimethenamid-P | 693 | 4 b | 5 b | 5 | 0.4 ab | 15.9 ab | 22 | 1.4 | 57 | 15.9 ab | 2.84 a |
Dimethenamid-P | 1386 | 8 c | 10 c | 2 | 0.9 ab | 15.8 ab | 18 | 1.2 | 53 | 16.4 bc | 2.68 ab |
Pyroxasulfone | 100 | 4 b | 4 b | 6 | 1.1 bc | 16.5 a | 23 | 1.4 | 56 | 15.7 ab | 2.78 ab |
Pyroxasulfone | 200 | 7 c | 9 c | 2 | 2.6 c | 14.6 b | 17 | 1.2 | 53 | 16.2 bc | 2.61 b |
Interaction | |||||||||||
V × H | NS | NS | * | NS | NS | * | ** | ** | NS | NS |
aAbbreviations: H, herbicide treatment; NS, not significant at P = 0.05 level; V, dry bean cultivar; WAE, weeks after crop emergence. bSignificance at P < 0. 05 and P < 0.01 levels denoted by * and **, respectively.
Dry bean injury (%) | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Herbicide treatment | Rate (g ai ha−1) | Adzuki | Kidney | SRM | White | |||||||||
Untreated check | 0 | a | 0 | a | 0 | a | 0 | a | ||||||
Pethoxamid | 1200 | 3 | b | 1 | b | 2 | bc | 4 | b | |||||
Pethoxamid | 2400 | 5 | bc | YZ | 2 | b | Z | 6 | d | YZ | 9 | c | Y | |
S-metolachlor | 1600 | 4 | b | 1 | b | 2 | bc | 2 | b | |||||
S-metolachlor | 3200 | 9 | cd | 2 | b | 4 | cd | 6 | bc | |||||
Dimethenamid-P | 693 | 4 | b | 1 | b | 2 | bc | 3 | b | |||||
Dimethenamid-P | 1386 | 9 | cd | Y | 2 | b | Z | 5 | d | YZ | 8 | c | Y | |
Pyroxasulfone | 100 | 4 | b | 2 | b | 1 | b | 3 | b | |||||
Pyroxasulfone | 200 | 14 | d | Y | 3 | b | Z | 4 | cd | YZ | 9 | c | YZ |
[
Dry bean biomass (g・m−1) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Herbicide treatment | Rate (g ai ha−1) | Adzuki | Kidney | SRM | White | ||||
Untreated check | 12 | a | 33 | a | 39 | a | 30 | a | |
Pethoxamid | 1200 | 12 | a | 31 | a | 33 | ab | 22 | bc |
Pethoxamid | 2400 | 9 | ab | 30 | a | 29 | b | 15 | d |
S-metolachlor | 1600 | 12 | a | 31 | a | 34 | ab | 23 | ab |
S-metolachlor | 3200 | 8 | ab | 33 | a | 31 | ab | 19 | bcd |
Dimethenamid-P | 693 | 10 | a | 31 | a | 31 | ab | 22 | bc |
Dimethenamid-P | 1386 | 9 | ab | 28 | a | 28 | b | 16 | cd |
Pyroxasulfone | 100 | 11 | a | 31 | a | 36 | ab | 22 | bc |
Pyroxasulfone | 200 | 7 | b | 28 | a | 28 | b | 17 | bcd |
aAbbreviations: PRE, preemergence; SRM, Small Red Mexican; WAE, weeks after crop emergence application.
(
Dry bean height (cm) | |||||||||
---|---|---|---|---|---|---|---|---|---|
Herbicide treatment | Rate (g ai ha−1) | Adzuki | Kidney | SRM | White | ||||
Untreated check | 43 | a | 57 | a | 72 | a | 61 | a | |
Pethoxamid | 1200 | 42 | ab | 56 | a | 70 | ab | 56 | abc |
Pethoxamid | 2400 | 40 | ab | 56 | a | 67 | b | 51 | d |
S-metolachlor | 1600 | 41 | ab | 55 | a | 70 | ab | 56 | abc |
S-metolachlor | 3200 | 39 | ab | 56 | a | 69 | ab | 55 | bcd |
Dimethenamid-P | 693 | 42 | ab | 57 | a | 69 | ab | 58 | ab |
Dimethenamid-P | 1386 | 40 | ab | 56 | a | 67 | b | 51 | d |
Pyroxasulfone | 100 | 42 | ab | 56 | a | 68 | ab | 58 | ab |
Pyroxasulfone | 200 | 38 | b | 55 | a | 67 | b | 52 | cd |
aAbbreviations: PRE, preemergence; SRM, Small Red Mexican; WAE, weeks after crop emergence application.
Group 15 herbicides applied PRE caused as much as 10%, 2%, 4% and 9% visible injury at 1 WAE, 11%, 3%, 6% and 10% visible injury at 2 WAE, and 2.5%, 0.5%, 0.7% and 0.8% visible injury at 8 WAE in adzuki, kidney, SRM and white bean, respectively (
At 4 WAE, pethoxamid, S-metolachlor, dimethenamid-P, and pyroxasulfone applied PRE caused 3 to 5, 4 to 9, 4 to 9 and 4% to 14% visible injury in adzuki bean, respectively (
Other studies have reported 2% to 20% injury and no adverse effect on dry weight and seed yield with pethoxamid applied PRE in adzuki bean [
Higher adzuki bean injury seen in this study with pyroxasulfone is similar to other studies. Stewart et al. [
Pethoxamid, S-metolachlor, dimethenamid-P, and pyroxasulfone applied PRE caused 3% or less visible injury at 4 WAE in kidney bean (
At 4 WAE, pethoxamid, S-metolachlor, dimethenamid-P, and pyroxasulfone applied PRE injured SRM bean 6%, 4%, 5% and 4% visible injury, respectively (
At 4 WAE, pethoxamid, S-metolachlor, dimethenamid-P, and pyroxasulfone applied PRE caused 4 to 9, 2 to 6, 3 to 8 and 3% to 9% visible injury in white bean, respectively (
At 1, 2 and 4 WAE, the Group 15 herbicides evaluated caused the greatest injury in adzuki bean, intermediate injury in white bean and least injury in SRM and kidney bean (
The Group 15 herbicides evaluated caused more injury in adzuki bean compared to kidney, SRM, and white beans. This is consistent with other findings that have shown variation in sensitivity of dry bean cultivars to herbicides including Group 15 herbicides [
Soltani, N., Shropshire, C. and Sikkema, P.H. (2018) Dry Bean Sensitivity to Group 15 Herbicides Applied Preemergence. American Journal of Plant Sciences, 9, 1414-1423. https://doi.org/10.4236/ajps.2018.97103