Locations In Ontario Research Articles

First report ofCotesia vanessae(Hymenoptera: Braconidae) in North America

AbstractWe report for the first time the occurrence of the well-known Eurasian and north African parasitoidCotesia vanessae(Reinhard) (Hymenoptera: Braconidae) in North America. Specimens were reared fromChrysodeixis chalcites(Esper) andTrichoplusia ni(Hübner) (Lepidoptera: Noctuidae) recovered from several locations in southwestern Ontario, Canada, and detected by DNA sequencing from oneAutographa californica(Speyer) (Lepidoptera: Noctuidae) in southern Alberta, Canada.

Response of Underseeded Red Clover (<i>Trifolium pratense</i> L.) to Winter Wheat (<i>Triticum aestivum</i> L.) Herbicides as Affected by Application Timing

Underseeding red clover in winter wheat is a beneficial agronomic practice. Still, many growers tend to forgo this approach. One reason is that herbicides used on winter wheat may injure underseeded red clover, reducing its biomass and the subsequent benefits it provides. Therefore, the effect of winter wheat herbicides on underseeded red clover needs to be evaluated. The objectives of this research were to assess the crop tolerance of underseeded red clover to ten winter wheat herbicides used in Ontario, Canada and determine if red clover tolerance differed when the herbicides were applied at various winter wheat growth stages. Experiments were conducted in 2009 and 2010 at four different Ontario locations. Each herbicide treatment was either applied at an early, normal or late timing. Overall, red clover was not affected by herbicides applied at the early timing. The likelihood of herbicides causing injury and reducing biomass of underseeded red clover increased when they were applied at the more advanced winter wheat growth stages. If timing is a constraint, the three herbicides bromoxynil/MCPA, tralkoxydim, and fenoxaprop-pethyl are the safest to use on red clover underseeded to winter wheat. The remaining herbicides 2,4-D, dicamba/MCPA/mecoprop, dichlorprop/2,4-D, thifensulfuron/ tribenuron + MCPA, fluroxypyr + MCPA, pyrasulfotole/bromoxynil, and prosulfuron + bromoxynil are more injurious, with the last two being the most harmful. By having identified the least damaging herbicides on underseeded red clover in winter wheat and the optimal timing for herbicide application, growers are more likely to adopt this beneficial agronomic practice, save on fertilizer costs and improve soil quality.

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

Twenty-two field experiments (six maize (Zea mays L.) and five soybean [Glycine max (L.) Merr.] using low glyphosate doses to assess weed control and six maize and five soybean using high glyphosate doses to assess tolerance) were conducted from 2010 to 2012 at two locations in southern Ontario, Canada to compare the commercially available glyphosate formulations of Roundup Weather MAX?, Clearout?41 Plus, and Wise Up? (WeatherMAX, Clearout, and WiseUp, respectively). Inmaize and soybean, control of velvetleaf, pigweed species, common lambs quarters, and green foxtail 4 weeks after treatment (WAT) using 900 g·ae·ha-1 ranged from at least 85% to 99%, regardless of formulation. By 8 WAT with 900 g·ae·ha-1, control of these weeds generally declined, but still ranged from 82% to 97% across all formulations. At harvest, maize yields were similar to the weed-free control for 900 g·ae·ha-1 of glyphosate as WeatherMAX and Clearout; however, reduced weed control with WiseUp resulted in an 8.8% yield loss. For soybean, yields were similar to the weed-free control, regardless of formulation or dose. In the tolerance experiments, 2.1% and 2.8% injury was observed 4 WAT for maize treated with 3600 g·ae·ha-1 of glyphosate as WeatherMAX and WiseUp, respectively. However, maize yields were unaffected by glyphosate formulation or dose. In soybean, visible injury of 8.5%, 4.5%, and 3.7% was observed 1 WAT with 5400 g·ae·ha-1 of glyphosate as WeatherMAX, WiseUp, and Clearout, respectively; by 8 WAT, visible injury was similar to the untreated control, regardless of formulation or dose. The early injury from 5400 g·ae·ha-1 of glyphosate resulted in 8.5%, 4.6%, and 5.5% yield loss for the WeatherMAX, WiseUp, and Clearout formulations, respectively.

Tolerance of Maize (<i>Zea mays</i> L.) and Soybean [<i>Glycine max</i> (L.) Merr.] to Late Applications of Postemergence Herbicides

Seven maize (Zea mays L.) and three soybean (Glycine max (L.) Merr.) field experiments were con- ducted from 2006 to 2009 at various locations in southern Ontario, Canada to determine the to- lerance of these crops to late applications of the maximum labeled herbicide dose. Single and se- quential (simulating a spray overlap) applications were evaluated for visible injury, plant height, and crop yield in the absence of weed competition. Maize exhibited excellent tolerance to herbi- cides applied at the 9- to 10-leaf growth stage as visible injury levels for almost all tested herbi- cides was similar to the untreated control 7 days after treatment (DAT). However, the sequential application of dicamba/diflufenzopyr or foramsulfuron caused 6 and 8% injury 7 DAT and 8 and 14% reduction in maize height 28 DAT, respectively. The observed injury and stunting were tran- sient as there were no differences in yield at harvest. Soybean displayed good tolerance to most herbicides applied at the 7th trifoliate leaf growth stage as visible injury levels were similar to the untreated control. However, thifensulfuron-methyl was injurious regardless of application and imazethapyr was injurious with sequential applications. For example, single thifensulfuron-me- thyl, sequential thifensulfuron-methyl, and sequential imazethapyr application treatments caused 35, 48, and 25% injury 7 DAT, respectively. Sequential thifensulfuron-methyl treatments also caused a 28 and 17% reduction in soybean height 14 and 28 DAT, respectively. Visual injury con- tinued to be detected up to 56 DAT for single thifensulfuron-methyl, sequential thifensulfuron- methyl, and sequential imazethapyr treatments. But, soybean yields were reduced by 10% for on- ly sequential thifensulfuron-methyl application treatments. For all other herbicides tested, the yields at harvest were similar to the untreated control. This research demonstrated that maize had exceptional tolerance to all the herbicides used in this study whereas soybean was tolerant to most of the herbicides used in this study. * Corresponding author.

Tolerance of Soybean (<i>Glycine max</i> L.) to Protoporphyrinogen Oxidase Inhibitors and Very Long Chain Fatty Acid Synthesis Inhibitors Applied Preemergence

Nine field experiments were conducted in 2011 and 2012 at various locations in southern Ontario, Canada to determine the tolerance of soybean (Glycine max (L.) Merr.) to herbicides inhibiting protoporphyrinogen oxidase (Protox) and very long chain fatty acid (VLCFA) synthesis applied alone and in combination. Preemergence applications were evaluated for soybean injury, plant height, shoot dry weight, and yield in the absence of weed competition. Early-season soybean injury from the Protox inhibitors persisted 4 weeks after soybean emergence (WAE) with 3%, 5%, and 18% injury for flumioxazin, saflufenacil, and sulfentrazone, respectively. When Protox inhibitors were tank mixed with VLCFA inhibitors (i.e., dimethenamid-P, S-metolachlor, and pyroxasulfone), additive interactions were observed for injury with saflufenacil and sulfentrazone; whereas synergistic interactions were observed with flumioxazin. However, injury subsided over time decreasing from as much as 34% injury 1 WAE for the flumioxazin + S-metolachlor tank mix down to 9% injury 4 WAE. In general, when saflufenacil or flumioxazin were tank mixed with VLCFA inhibitors, greater than expected reductions in height and dry weight were observed indicating synergistic responses; while no interactive effects were detected with sulfentrazone and VLCFA inhibitor tank mixes. For the flumioxazin tank mixes that contained dimethenamid-P or S-metolachlor, the reduction in yield was greater than expected indicating synergistic interactive effects. Yet, all the demonstrated impacts were transient as the yield for soybean treated with any of the Protox inhibitor and VLCFA inhibitor tank mixes tested were similar to the untreated control. Therefore, usage restriction on these mixtures, based on perceived negative yield impact, should be lifted so the herbicides could be combined to expand weed control options.

The Effect of Time of Day on the Activity of Postemergence Soybean Herbicides

The effect of time of day (TOD) on the activity of six common POST herbicides was investigated in field trials from 2007 to 2009 at two locations in southwestern Ontario. Percentage weed control was assessed following application of bentazon, chlorimuron-ethyl, fomesafen, glyphosate, imazethapyr, or quizalofop-p-ethyl applied at 3-h intervals from 6:00 A.M. to midnight, when weeds averaged 15 cm tall. The effect of time of day varied with weed species, but weed control was generally reduced when herbicides were applied at 6:00 A.M., 9:00 P.M., and midnight. Herbicide activity on velvetleaf was most frequently reduced, especially for chlorimuron-ethyl, glyphosate, and imazethapyr. Control of common ragweed with glyphosate and imazethapyr was also affected by the timing of application, and pigweed species only showed an effect with glyphosate. Variation in temperature, relative humidity, and dew presence/absence at different times of the day, as well as morphological/physiological characteristics such as weed size at time of application and diurnal leaf movement in response to light intensity, may account for the variation in weed control at different times of the day. Significant soybean yield loss was not observed in this study, but may occur if herbicide efficacy is severely reduced by application at inappropriate times of day. These results provide valuable information for growers, and suggest that POST herbicides are most effective when applied midday, rather than in the early morning or late evening.

A spatial analysis of private well water Escherichia coli contamination in southern Ontario

Research to date has provided limited insight into the complexity of water-borne pathogen transmission. Private well water supplies have been identified as a significant pathway in infectious disease transmission in both the industrialised and the developing world. Using over 90,000 private well water submission records representing approximately 30,000 unique well locations in south-eastern Ontario, Canada, a spatial analysis was performed in order to delineate clusters with elevated risk of E. coli contamination using 5 years of data (2008-2012). Analyses were performed for all years independently and subsequently compared to each other. Numerous statistically significant clusters were identified and both geographic stability and variation over time were examined. Through the identification of spatial and temporal patterns, this study provides the basis for future investigations into the underlying causes of bacterial groundwater contamination, while identifying geographic regions that merit particular attention to public health interventions and improvement of water quality.

Weed Control, Environmental Impact and Profitability of Two-Pass Weed Management Strategies in Glyphosate-Resistant Corn

Twelve field trials were conducted over a three-year period (2010, 2011, 2012) at different locations in southwestern Ontario, Canada to compare various two-pass weed management strategies in glyphosate-resistant corn for crop injury, weed control, environmental impact, corn yield and profit margin. No visible injury resulted from the herbicide treatments evaluated. One early postemergence (EPOST) application of glyphosate provided good full season control of pigweed species and lady's thumb and fair control of velvetleaf, common ragweed, lamb's-quarters, barnyard grass and green foxtail. One late postemergence (LPOST) application of glyphosate provided excellent control of all weed species evaluated but corn yield was reduced due to early weed interference. The sequential application of glyphosate (EPOST fb LPOST) provided excellent control of all weed species evaluated with no adverse effect on corn yield. The sequential application of a preemergence residual herbicide followed by an application of glyphosate LPOST provided excellent full season control of all weed species evaluated and corn yield was equal to the weed free control. Among the sequential herbicide programs the lowest environmental impact was glyphosate EPOST fb LPOST and saflufenacil/dimethenamid-p, isoxaflutole + atrazine or rimsulfuron + s-metolachlor + dicamba applied PRE fb glyphosate LPOST. Based on this study, the most efficacious and profitable weed management programs in glyphosate-resistant corn are a sequential application of glyphosate or a two-pass program of a preemergence residual herbicide followed by glyphosate LPOST. The two-pass programs have glyphosate stewardship benefits.

Weed management in white beans with postemergence herbicide tankmixes

Soltani, N., Nurse, R. E. and Sikkema, P. H. 2013. Weed management in white beans with postemergence herbicide tankmixes. Can. J. Plant Sci. 93: 669–674. Weed control efficacy of cloransulam-methyl, halosulfuron, bentazon, fomesafen and their tankmixes applied post-emergence (POST) for weed management in white bean was evaluated in field studies conducted in four Ontario locations during 2008–2011. Cloransulam-methyl, halosulfuron, bentazon, fomesafen, bentazon plus fomesafen, cloransulam-methyl plus bentazon, cloransulam-methyl plus fomesafen, cloransulam-methyl plus bentazon plus fomesafen, halosulfuron plus bentazon, halosulfuron plus fomesafen, and halosulfuron plus bentazon plus fomesafen caused white bean injury ranging from 1 to 18%. Control for AMARE, AMBEL and CHEAL ranged from 47 to 92%, 66 to 98% and 36 to 91%, respectively, among herbicide treatments. Similar results were observed for weed density and biomass of AMARE, AMBEL, and CHEAL. Cloransulam-methyl, halosulfuron, and cloransulam-methyl plus fomesafen reduced the yield of white bean by 34, 21, and 17%, respectively, compared with the weed-free control. However, bentazon, fomesafen, bentazon plus fomesafen, cloransulam-methyl plus bentazon, cloransulam-methyl plus bentazon plus fomesafen, halosulfuron plus bentazon, halosulfuron plus fomesafen, and halosulfuron plus bentazon plus fomesafen had no adverse effect on yield of white bean. Based on these results, tankmixes of cloransulam-methyl and halosulfuron with bentazon and fomesafen can reduce crop injury and provide control of broadleaf weeds in white bean.

Winter wheat (Triticum aestivum L.) tolerance to mixtures of herbicides and fungicides applied at different timings

Robinson, M. A., Cowbrough, M. J., Sikkema, P. H. and Tardif, F. J. 2013. Winter wheat (Triticum aestivum L.) tolerance to mixtures of herbicides and fungicides applied at different timings. Can. J. Plant Sci. 93: 491–501. Farmers commonly tank-mix herbicides and fungicides to reduce application costs. In the spring of 2008, there were reports of winter wheat injury with the application of herbicide–fungicide tank-mixes early in the growing season. This study was established to determine the tolerance of winter wheat to herbicide–fungicide mixtures as influenced by time of application. Field studies were conducted at four Ontario locations in 2009 and 2010 with three herbicides and four fungicides. Herbicide–fungicide tank-mixes were applied early, under cold conditions, and late at growth stage Zadoks 37–39. Dichlorprop/2,4-D mixed with tebuconazole caused up to 15% injury when applied early and up to 29% injury when applied late. Bromoxynil/MPCA mixed with tebuconazole injured wheat up to 15% when applied early but only 10% when applied late. Other herbicide and fungicide mixes caused a lower level of injury. Visible injury was transient and did not reduce winter wheat yields. The likelihood of tank-mixes causing injury was greater when they were applied late. The fungicide tebuconazole caused the highest level of injury when mixed with herbicides and injury was particularly high with dichlorprop/2,4-D.

Effect of harvest date on barley grain contamination with Fusarium spp. and deoxynivalenol in northeastern Ontario

The effect of harvest date on the incidence of seed-borne Fusarium spp. and deoxynivalenol (DON) concentration in barley (Hordeum vulgare L.) was studied using three cultivars at three locations in Ontario in both 2004 and 2005. The profile of seed-borne Fusarium spp. was dominated by F. equiseti (Corda) Sacc., F. sporotrichioides Sherb., and F. poae (Peck) Wollenw., isolated from 4.4%, 3.3%, and 1.6% of the kernels, representing 39.3%, 29.4%, and 14.2% of the Fusarium pathogen population, respectively. Fusarium graminearum Schwabe and F. avenaceum (Fr.) Sacc. were each recovered from <1% of the kernels and represented 8.3% and 6.6% of the pathogen population, respectively. Other species, including F. acuminatum Ellis & Everh., F. culmorum (W.G. Sm.) Sacc., and F. semitectum Berk. & Rav., collectively occurred only on 0.2% of all kernels and represented <2% of the population. The incidence level of all Fusarium spp. increased from 6.9 to 13.9% when harvest was delayed. Of the commonly recovered species, only F. avenaceum and F. sporotrichioides levels increased with the delayed harvest, while other species did not follow a clear pattern. DON concentration in the harvested grain ranged from 0.20 to 0.28 mg kg‑1 with the five harvest dates, and was not statistically different. Significant differences in the incidence of all Fusarium spp. and in DON concentration were observed among cultivars, locations, and between the 2 yr of the study. The highest DON concentration observed in this study was 0.5 mg kg‑1, which is below the Canadian tolerance level of 1.0 mg kg‑1.

Genetic basis of soybean adaptation to North American vs. Asian mega-environments in two independent populations from Canadian × Chinese crosses

One of the goals of plant breeding is to increase yield with improved quality characters. Plant introductions (PI) are a rich source of favorable alleles that could improve different characters in modern soybean [Glycine max (L.) Merril] including yield. The objectives of this study were to identify yield QTL underlying the genetic basis for differential adaptation of soybeans to the Canadian, United States or Chinese mega-environments (ME) and to evaluate the relationship and colocalization between yield and agronomic traits QTL. Two crosses between high-yielding Canadian cultivars and elite Chinese cultivars, OAC Millennium×Heinong 38 and Pioneer 9071×#8902, were used to develop two recombinant inbred line (RIL) populations. Both populations were evaluated at different locations in Ontario, Canada; Minnesota, United States (US), Heilongjiang and Jilin, China, in 2009 and 2010. Significant variation for yield was observed among the RILs of both populations across the three hypothetical ME. Two yield QTL (linked to the interval Satt364-Satt591 and Satt277) and one yield QTL (linked to marker Sat_341) were identified by single-factor ANOVA and interval mapping across all ME in populations 1 and 2, respectively. The most frequent top ten high-yielding lines across all ME carried most of the high-yielding alleles of the QTL that were identified in two and three ME. Both parents contributed favorable alleles, which suggests that not only the adapted parent but also the PI parents are potential sources of beneficial alleles in reciprocal environments. Other QTL were detected also at two and one ME. Most of the yield QTL were co-localized with a QTL associated with an agronomic trait in one, two, or three ME in just one or in both populations. Results suggested that most of the variation observed in seed yield can be explained by the variation of different agronomic traits such a maturity, lodging and height. Novel alleles coming from PI can favorably contribute, directly or indirectly, to seed yield and the utilization of QTL detected across one, two or three ME would facilitate the new allele introgression into breeding populations in both North America and China.

Using the candidate gene approach for detecting genes underlying seed oil concentration and yield in soybean

Increasing the oil concentration in soybean seeds has been given more attention in recent years because of demand for both edible oil and biodiesel production. Oil concentration in soybean is a complex quantitative trait regulated by many genes as well as environmental conditions. To identify genes governing seed oil concentration in soybean, 16 putative candidate genes of three important gene families (GPAT: acyl-CoA:sn-glycerol-3-phosphate acyltransferase, DGAT: acyl-CoA:diacylglycerol acyltransferase, and PDAT: phospholipid:diacylglycerol acyltransferase) involved in triacylglycerol (TAG) biosynthesis pathways were selected and their sequences retrieved from the soybean database ( http://www.phytozome.net/soybean ). Three sequence mutations were discovered in either coding or noncoding regions of three DGAT soybean isoforms when comparing the parents of a 203 recombinant inbreed line (RIL) population; OAC Wallace and OAC Glencoe. The RIL population was used to study the effects of these mutations on seed oil concentration and other important agronomic and seed composition traits, including seed yield and protein concentration across three field locations in Ontario, Canada, in 2009 and 2010. An insertion/deletion (indel) mutation in the GmDGAT2B gene in OAC Wallace was significantly associated with reduced seed oil concentration across three environments and reduced seed yield at Woodstock in 2010. A mutation in the 3' untranslated (3'UTR) region of GmDGAT2C was associated with seed yield at Woodstock in 2009. A mutation in the intronic region of GmDGAR1B was associated with seed yield and protein concentration at Ottawa in 2010. The genes identified in this study had minor effects on either seed yield or oil concentration, which was in agreement with the quantitative nature of the traits. However, the novel gene-specific markers designed in the present study can be used in soybean breeding for marker-assisted selection aimed at increasing seed yield and oil concentration with no significant impact on seed protein concentration.

Effects of region and cultivar on alkylresorcinols content and composition in wheat bran and their antioxidant activity

This study evaluated the effects of cultivar and region on the composition of alkylresorcinols (ARs) of 24 wheat bran samples from 6 cultivars grown in four locations (Bath, Nairn, Palmerstone and Ridgetown) in Ontario (ON), Canada, using gas chromatography/mass spectrometry (GC/MS). Total phenolic content (TPC) of wheat bran extracts was determined by the Folin–Ciocalteau method and the antioxidant activity of wheat bran extracts was measured by 2, 2-Dipheny-1-picryhydrazyl radical (DPPH) scavenging activity and oxygen radical absorbance capacity (ORAC). The highest ARs content (μg/g) was found in cultivars Emmit (1522), Harvard (1305), Warthog (1170), and Superior (853), grown in Ridgetown. The relative saturated and unsaturated ARs (%) were 89 and 11, respectively. Total ARs content, their composition, TPC and antioxidant activity of wheat bran extracts were significantly (P < 0.05) affected by location and cultivar and their interaction. TPC, %DPPHdis, and ORAC values for different wheat bran sample extracts ranged from 3 to 58 (mg FAE/g), 5 to 68 (%), and 6 to 94 (μmol TE/g), respectively. Our work provides a detailed examination of region and cultivar effects on potential of ARs in wheat bran and the results can be used for screening and breeding purposes.

Pheromone-Based Action Thresholds for Control of the Swede Midge, &lt;I&gt;Contarinia nasturtii&lt;/I&gt; (Diptera: Cecidomyiidae), and Residual Insecticide Efficacy in Cole Crops

The swede midge, Contarinia nasturtii (Kieffer), is an invasive gall midge causing economic damage to cole crops (Brassica oleracea L.) and other crucifers in eastern Canada and United States. An effective decision-making tool for timing insecticide applications is a critical part of an integrated pest management program against C. nasturtii. Experiments were undertaken over 2 yr and at three locations in southern Ontario to develop pheromone-based action thresholds for C. nasturtii in cabbage and broccoli. An economic comparison between action threshold and calendar insecticide regimes was undertaken. The threshold approach was both economically viable and successful at minimizing swede midge damage for cabbage, and an action threshold of five males per trap per day with a minimum 7 d retreatment interval successfully reduced damage to acceptable levels. However, this approach was not successful with broccoli, which, unlike cabbage, is susceptible to damage by C. nasturtii through all plant stages, including heading. Acetamiprid and lambda-cyhalothrin both demonstrated approximately 7 d residual activity against C. nasturtii. Registration labels for both insecticides specify a minimum 7 d retreatment interval, which is supported by residual efficacy results. More effective insecticidal products may have longer residual efficacy and improve efficacy of the action threshold approach for broccoli and cabbage.

Effect of imazethapyr application timing in kidney and white bean

A total of twelve field trials (6 with kidney bean and 6 with white bean) were conducted over a three-year period (2010 to 2012) at various locations in Ontario to evaluate the tolerance of kidney and white bean to imazethapyr applied preplant incorporated (PPI), preemergence (PRE), and postemergence (POST) at 37.5, 75 and 150 g·ai·ha-1. Imazethapyr applied PPI or PRE in kidney or white bean caused 0%-1%, 0%-4%, and 0%-9% injury at 1, 2, and 4 weeks after application (WAA), respectively. However, the injury was transient and had no adverse effect on shoot dry weight, height, seed moisture content, and yield of kidney or white bean except for shoot dry weight which was reduced 32% with imazethapyr applied PPI compared to the weed free control in white bean. Imazethapyr applied POST in kidney or white bean caused as much as 17%, 18%, and 11% injury at 1, 2, and 4 WAA, respectively. There was no adverse effect on shoot dry weight, height, seed moisture content, and yield of kidney or white bean except for imazethapyr applied POST which increased seed moisture content 1.9% compared to the weed free control in white bean. Based on these results, there is an adequate margin of crop safety in dry bean to imazethapyr applied PPI or PRE at 37.5 or 75 g·ai·ha-1 in kidney and white beans. However, there is not an adequate margin of crop safety for imazethapyr applied POST at rates higher than 37.5 g·ai·ha-1 in kidney and white bean.

Soybean (Glycine max) cultivar tolerance to saflufenacil

Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Soybean (Glycine max) cultivar tolerance to saflufenacil. Can. J. Plant Sci. 92: 1319–1328. Six field studies were conducted over a 2-yr period (2009 and 2010) at three Ontario locations to determine the sensitivity of 12 glyphosate-resistant soybean cultivars to saflufenacil applied preemergence (PRE). The level of crop injury was dependent on environmental conditions shortly after application. When soybean emergence was delayed due to cool, wet conditions following planting, 52 and 59 g a.i. ha−1 of saflufenacil resulted in 10% injury 1 wk after emergence (WAE) in cultivars OAC Hanover and RCAT Matrix, respectively. In the other environments, greater than 200 g a.i. ha−1 of saflufenacil was required to induce the same level of injury at 1 WAE. Injury decreased with time; however, the more sensitive soybean cultivars were unable to recover from early-season injury sustained under adverse environmental conditions. A hydroponic bioassay was developed to screen differences in soybean tolerance to saflufenacil. OAC Hanover was more sensitive than all the other cultivars in both field and hydroponic testing (P&lt;0.05). OAC Hanover yield was reduced regardless of environmental conditions. Under cool, wet conditions, 22 g a.i. ha−1 of saflufenacil resulted in a 10% yield reduction, while 46 g a.i. ha−1 was needed under warm dry conditions. All other cultivars required between 82 and 146 g a.i. ha−1 to obtain the same level of yield reduction. This research demonstrates that there is a difference in soybean cultivar sensitivity to saflufenacil applied PRE.

Cold temperature and emerald ash borer: Modelling the minimum under-bark temperature of ash trees in Canada

The potential range of forest pest species can depend on climate conditions. Predicting the effects of climate on insect species may be complicated, however, by the need to translate routinely collected meteorological data into microclimate measurements. For example, tree-boring beetles which spend the winter months in the under-bark microclimate (e.g., emerald ash borer (Agrilus planipennis Fairmaire), mountain pine beetle (Dendroctonus ponderosae Hopkins)) may experience minimum temperatures that tend to be warmer than air temperature minima. Moreover, the magnitude of the difference between under-bark and air temperature minima is variable, meaning that models of under-bark temperature cannot assume a constant level of thermal buffering.We used a Newtonian cooling model to predict the winter under-bark temperature minima of ash trees (Fraxinus spp.) in woodlots and urban centers in Canada. In order to capture a wide range of temperature extremes and patterns experienced by emerald ash borer or other deciduous-feeding tree-boring beetles, the model was parameterized and tested using hourly temperature data from two winters for 24 different ash trees in urban and woodlot sites across 6 different Ontario locations. The model was tested using a subset of the Ontario data and data from Alberta and Saskatchewan. Average model prediction errors (e.g., 1.31°C root mean squared error for Ontario) were much smaller than errors associated with assuming a constant level of buffering of 1°C (2.61°C). Modifications of the model to account for elevation and solar radiation did not offer any improvement in model fit, although accounting for urban heat island effects offered some improvement.An attempt was made to model daily temperature maxima, but even when the model was modified to include solar radiation, it was not accurate at predicting daily temperature maxima, possibly because of complex shading and heating patterns that can occur during warmer parts of the day in urban and woodlot environments. We conclude that this model is suitable for modelling minimum under-bark temperature across a range of latitudes and longitudes for both deciduous and coniferous trees in urban and woodlot settings.

Biologically effective rate of saflufenacil/dimethenamid-p in soybean (Glycine max)

Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Biologically effective rate of saflufenacil/dimethenamid- in soybean (Glycine max). Can. J. Plant Sci. 92: 517–531. A total of five field studies were conducted over a 2-yr period (2009, 2010) at three Ontario locations to determine the biologically effective rate of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. The rate of saflufenacil/dimethenamid-p required for the control of annual weeds was influenced by environmental conditions. With adequate moisture and above-average temperatures in 2010, between 224 and 374 g a.i. ha-1 of saflufenacil/dimethenamid-p was required for 80% control of common ragweed, common lamb's quarters, and green foxtail 4 wk after treatment (WAT). In contrast, below-average temperatures and excessive moisture in 2009 resulted in higher rates of saflufenacil/dimethenamid-p being necessary for the same level of weed control. Pigweed species were l...

Biologically effective rate of saflufenacil/dimethenamid-p in soybean (Glycine max)

Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Biologically effective rate of saflufenacil/dimethenamid- in soybean ( Glycine max ). Can. J. Plant Sci. 92: 517–531. A total of five field studies were conducted over a 2-yr period (2009, 2010) at three Ontario locations to determine the biologically effective rate of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. The rate of saflufenacil/dimethenamid-p required for the control of annual weeds was influenced by environmental conditions. With adequate moisture and above-average temperatures in 2010, between 224 and 374 g a.i. ha−1 of saflufenacil/dimethenamid-p was required for 80% control of common ragweed, common lamb's quarters, and green foxtail 4 wk after treatment (WAT). In contrast, below-average temperatures and excessive moisture in 2009 resulted in higher rates of saflufenacil/dimethenamid-p being necessary for the same level of weed control. Pigweed species were least affected by environmental conditions after application at 4 WAT with only 245 g a.i. ha−1 required for 80% control in both years. By 11 WAT, 320 g a.i. ha−1 or less of saflufenacil/dimethenamid-p was required to achieve 80% control of these species in 2010, while 845 g a.i. ha−1 or more was needed in 2009 for equivalent control. The potential of saflufenacil/dimethenamid-p as a set-up treatment prior to a postemergence (POST) glyphosate application was also examined. Excellent full season control of all weed species was achieved with saflufenacil/dimethenamid-p applied PRE followed by glyphosate POST. However, there was no difference in yield when saflufenacil/dimethenamid-p was followed by glyphosate POST compared with a single glyphosate POST application.