Farmer training is important to improve weed management practices in tea cultivation. To explore the group characteristics of tea growers, we interviewed 354 growers in Guizhou Province, China. Sixty-one percent of the respondents planted tea for companies or cooperative groups, and 56% managed tea gardens larger than 10 ha. Self-employed tea growers tended to be older and smallholders, and to apply herbicides and conduct weed control less frequently (P < 0.05). Approximately 87% of the respondents conducted weed control two to four times yr−1, 83% spent between $200 and $2,000 ha−1 yr−1 for weed control, and 42% thought weed control costs would decrease by 5 years from this study. Twenty-eight species were mentioned by the respondents as being the most serious. According to canonical correspondence analysis, latitude, altitude, being self-employed or a member of a cooperative, having training experience in tea-garden weed management, and frequency and cost of weed control in tea gardens had significant (P < 0.05) influence on the composition of most troublesome weed species listed by respondents. Among the respondents, 60% had had farmer’s training on weed management in tea gardens. Of these, a significant number (P < 0.05) tended to think weed control costs would decrease, and a nonsignificant number (P > 0.05) tended to conduct weed control more frequently and have lower weed management costs in their tea gardens.

Tomato is injured by low doses of 2,4-D, dicamba, quinclorac, and glyphosate. New crop varieties resistant to 2,4-D and dicamba are likely to increase use of these herbicides and may increase drift problems. There is a diverse germplasm of tomato available that includes wild relatives known to be tolerant to numerous biotic and abiotic stresses. A greenhouse and field study was conducted to investigate auxin tolerance in three wild tomato accessions (TOM199, TOM198, and TOM300) and compare them with two commercial tomato cultivars (‘Money Maker’ and ‘Better Boy’). Auxin herbicides, which included 2,4-D, dicamba, and quinclorac, were applied at doses of 11, 3, and 39 g ae ha−1, respectively. Visible injury ratings of each accession for each herbicide treatment were recorded at 7, 14, 21, and 28 d after treatment (DAT) on a 0% to 100% scale. Results indicate that all three wild tomato accessions exhibited less than 15% injury compared with 100% injury for two commercial cultivars after application of dicamba. The three wild accessions (TOM199, TOM198, and TOM300) did not show any significant reduction in plant height compared with nontreated plants. At 28 DAT, plant heights of TOM199, TOM198, and TOM300 were 25, 25, and 28 cm when treated with dicamba and 31, 30, and 31 cm nontreated, respectively. Based on these results, the identified lines can serve as a genetic resource for developing herbicide-tolerant tomato, thus minimizing or eliminating the negative impacts of drift from nonlabeled herbicides tested in this project.

Field experiments were conducted in 2012 and 2013 across four locations for a total of 6 site-years in the midsouthern United States to determine the effect of growth stage at exposure on soybean sensitivity to sublethal rates of dicamba (8.8 g ae ha−1) and 2,4-D (140 g ae ha−1). Regression analysis revealed that soybean was most susceptible to injury from 2,4-D when exposed between 413 and 1,391 accumulated growing degree days (GDD) from planting, approximately between V1 and R2 growth stages. In terms of terminal plant height, soybean was most susceptible to 2,4-D between 448 and 1,719 GDD, or from V1 to R4. However, maximum susceptibility to 2,4-D was only between 624 and 1,001 GDD or from V3 to V5 for yield loss. As expected, soybean was sensitive to dicamba for longer spans of time, ranging from 0 to 1,162 GDD for visible injury or from emergence to R2. Likewise, soybean height was most affected when dicamba exposure occurred between 847 and 1,276 GDD or from V4 to R2. Regarding grain yield, soybean was most susceptible to dicamba between 820 and 1,339 GDD or from V4 to R2. Consequently, these data indicate that soybean response to 2,4-D and dicamba can be variable within vegetative or reproductive growth stages; therefore, specific growth stage at the time of exposure should be considered when evaluating injury from off-target movement. In addition, application of dicamba near susceptible soybean within the V4 to R2 growth stages should be avoided because this is the time of maximum susceptibility. Research regarding soybean sensitivity to 2,4-D and dicamba should focus on multiple exposure times and also avoid generalizing growth stages to vegetative or reproductive.

Dicamba-resistant (DR) kochia is an increasing concern for growers in the US Great Plains, including Kansas. Greenhouse and field experiments (Garden City and Tribune, KS, in the 2014 to 2015 growing season) were conducted to characterize the dicamba resistance levels in two recently evolved DR kochia accessions collected from fallow fields (wheat–sorghum–fallow rotation) near Hays, KS, and to determine the effectiveness of various PRE herbicide tank mixtures applied in fall or spring prior to the fallow year. Dicamba dose–response studies indicated that the KS-110 and KS-113 accessions had 5- to 8-fold resistance to dicamba, respectively, relative to a dicamba-susceptible (DS) accession. In separate field studies, atrazine-based PRE herbicide tank mixtures, dicamba + pendimethalin + sulfentrazone, and metribuzin + sulfentrazone when applied in the spring had excellent kochia control (85% to 95%) for 3 to 4 mo at the Garden City and Tribune sites. In contrast, kochia control with those PRE herbicide tank mixtures when applied in the fall did not exceed 79% at the later evaluation dates. In conclusion, the tested kochia accessions from western Kansas had evolved moderate to high levels of resistance to dicamba. Growers should utilize these effective PRE herbicide tank mixtures (multiple sites of action) in early spring to manage kochia seed bank during the summer fallow phase of this 3-yr crop rotation (wheat–corn/sorghum–fallow) in the Central Great Plains.

During 2016 and 2017, four field experiments were conducted at Huron Research Station near Exeter, ON, to evaluate the sensitivity of dry bean grown under a strip-tillage cropping system, to potential herbicides for the control of glyphosate-resistant (GR) horseweed. At 8 wk after emergence (WAE), saflufenacil, metribuzin, saflufenacil+metribuzin, 2,4-D ester, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl caused 13% to 32%, 8% to 52%, 32% to 53%, 5% to 7%, 13% to 21%, 16% to 29%, and 23% to 43% visible injury in dry beans, respectively. Saflufenacil decreased aboveground biomass 65% in kidney bean and 80% in white bean. Metribuzin decreased biomass 82% in kidney bean and 50% in white bean. Saflufenacil+metribuzin decreased biomass 88% in kidney bean, 68% in small red bean, and 80% in white bean. Chlorimuron-ethyl decreased biomass 40% in white bean. There was no decrease in dry bean biomass with the other herbicides evaluated. Metribuzin and saflufenacil+metribuzin reduced kidney bean seed yield 72% and 76%, respectively. Saflufenacil+metribuzin, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl reduced small red bean seed yield 39%, 27%, 30%, and 54%, respectively. Saflufenacil, metribuzin, saflufenacil+metribuzin, flumetsulam, cloransulam-methyl, and chlorimuron-ethyl reduced seed yield of white bean 52%, 32%, 62%, 33%, 42%, and 62%, respectively. There was no decrease in dry bean yield with the other herbicides evaluated. Among herbicides evaluated, 2,4-D ester caused the least crop injury with no effect in dry bean seed yield.

Field and greenhouse studies were conducted to evaluate the antagonism potential of glufosinate applied sequentially or mixed with graminicides on barnyardgrass control. Applications of glufosinate alone provided variable control throughout the growing season in both field and greenhouse experiments. In the field, barnyardgrass control was not adversely affected by glufosinate- and clethodim-mix applications or sequential applications of glufosinate before or after clethodim. Soybean yield was not affected by application timing or clethodim rate, with yield ranging from 1,748 to 2,733 kg ha−1. In the greenhouse, glufosinate applied 1 and 3 d before graminicides generally reduced barnyardgrass control compared with the graminicides applied alone. The response with quizalofop-P was not as dramatic as with the other graminicides. Although significant visual barnyardgrass control differences were detected due to application timing of glufosinate, barnyardgrass biomass with fluazifop-P and quizalofop-P did not differ between the application timings of glufosinate. However, glufosinate applied 1 and 3 d before clethodim had significantly greater biomass compared with glufosinate applied 1 and 3 d after clethodim. The differences in environmental conditions and growth stages at the time of application may have contributed to barnyardgrass control response differences between the field and greenhouse experiments. Although barnyardgrass control in the field was not affected by glufosinate application timing, data from the greenhouse indicate potential exists for reduced control if glufosinate is applied 1 or 3 d before graminicides.

Great Plains yucca is a native species that competes with forage plants for space and water and at high densities may warrant control. The objective of this study was to determine the efficacy of seven herbicides applied in the spring or fall for Great Plains yucca control. Six foliar herbicides applied by ground application at 187 L ha−1 spray volume, one herbicide applied to individual plant whorls, and a nontreated check were established in June and September of 2009 and 2011. Percent mortality was determined 12 to 16 mo after herbicide application. Most herbicides gave similar control between the 2 yr, with triclopyr in diesel applied to individual plant whorls at 10 g L−1 providing the greatest control at 83%. Most herbicides applied in June near the blooming stage of Great Plains yucca were more effective than September treatments. June treatments providing the greatest reduction in yucca densities were metsulfuron + dicamba + 2,4-D amine + 2,4-D low volatile ester (LVE) at 21 + 113 + 325 + 431 g ae ha−1, metsulfuron + aminopyralid + triclopyr at 49 + 9 + 227 g ha−1, metsulfuron + chlorsulfuron + 2,4-D LVE at 34 + 11 + 431 g ha−1, and metsulfuron + aminopyralid + 2,4-D LVE at 49 + 9 + 431 g ha−1. A single application of a foliar herbicide provided a maximum of 72% mortality of Great Plains yucca, suggesting that repeat application may be necessary to achieve optimum control.

Sugarbeet, grown for biofuel, is being considered as an alternate cool-season crop in the southeastern United States. Previous research identified ethofumesate PRE and phenmedipham + desmedipham POST as herbicides that controlled troublesome cool-season weeds in the region, specifically cutleaf evening-primrose. Research trials were conducted from 2014 through 2016 to evaluate an integrated system of sweep cultivation and reduced rates of ethofumesate PRE and/or phenmedipham+desmedipham POST for weed control in sugarbeet grown for biofuel. There were no interactions between the main effects of cultivation and herbicides for control of cutleaf evening-primrose and other cool-season species in two out of three years. Cultivation improved control of cool-season weeds, but the effect was largely independent of control provided by herbicides. Of the herbicide combinations evaluated, the best overall cool-season weed control was from systems that included either a 1/2X or 1X rate of phenmedipham+desmedipham POST. Either rate of ethofumesate PRE was less effective than phenmedipham+desmedipham POST. Despite improved cool-season weed control, sugarbeet yield was not affected by cultivation each year of the study. Sugarbeet yields were greater when treated with any herbicide combination that included either a 1/2X or 1X rate of phenmedipham+desmedipham POST compared with either rate of ethofumesate PRE alone or the nontreated control. These results indicate that cultivation has a very limited role in sugarbeet grown for biofuel. The premise of effective weed control based on an integration of cultivation and reduced herbicide rates does not appear to be viable for sugarbeet grown for biofuel.

Across the southeastern United States, pyridine carboxylic acid herbicides are widely used for broadleaf weed control in permanent grass pastures. This family of herbicides has proved very successful for controlling most broadleaf weeds commonly present in southeastern pastures and hayfields. In the southern United States, producers have expressed concern when overseeding legume species into warm-season perennial sods following application of commonly used pyridine carboxylic acid herbicides, as legumes are generally highly sensitive to this herbicide family. Field experiments were established to evaluate two herbicide treatment programs (residual vs nonresidual) on crimson clover overseeded into bermudagrass sod. The residual herbicide program included aminopyralid plus 2,4-D (0.09 + 0.7 kg ae ha–1), and the nonresidual program included triclopyr plus fluroxypyr (0.63 + 0.21 kg ae ha–1) plus 2,4-D (1.12 kg ae ha–1). Herbicide programs were applied at two key timings: in spring (May) and early summer (June). Spring applications were also evaluated when used in single vs repeated annual application. Our results did not indicate soil residual herbicide issues for crimson clover planted in the fall following spring or early-summer application of aminopyralid + 2,4-D at either location. Additionally, there were no cumulative negative impacts on crimson clover following 2 yr of spring herbicide application. Crimson clover cover, however, strongly decreased as grass and weed cover increased––an event that may be related to greater interspecific competition at higher levels of grass and weed cover. Soil fertility, weather, and competition from resident annual grasses and weeds strongly influenced productivity, suggesting that changes in pasture dynamics had a greater influence on clover productivity than did herbicide treatment or timing of application.

Dicamba-resistant crops are being rapidly embraced by growers in the United States to manage glyphosate-resistant and other difficult-to-control broadleaf weeds. However, dicamba resistance in kochia, one of the troublesome weeds of the North American Great Plains, is already widespread. Hence, POST application of dicamba may not adequately control kochia. In recent years in the High Plains Region of Colorado, Kansas, and Nebraska, dicamba has been widely applied, often in combination with atrazine or metribuzin, in early spring for PRE control of kochia. However, there is concern this use pattern may increase the selection for dicamba-resistant (DR) kochia. Hence, there is need to understand the efficacy of dicamba applied PRE versus POST for managing DR kochia. A greenhouse study was conducted to test the efficacy of PRE-applied dicamba compared with POST application using both DR and dicamba-susceptible (DS) kochia. Efficacies of PRE-applied dicamba were compared at seeding densities of 300, 600, 900 and 1200 viable seed m−2. At eight weeks after PRE and four weeks after POST treatment, control of DR kochia seeded at 300 viable seed m−2 was improved from 10% with 560 g ae ha−1 dicamba applied POST to 94 and 97% with 350 and 420 g ha−1 dicamba applied PRE, respectively. However, the efficacy of PRE-applied dicamba was negatively correlated with seed density. When kochia seeding density was increased from 300 to 1200 seed m−2, the ED50 of PRE-applied dicamba increased from 237 to 705 g ae ha−1 for DR kochia, and from 129 to 361 g ae ha−1 for DS kochia, respectively. Thus, PRE-applied dicamba was effective in controlling the population of DR kochia tested, suggesting that PRE-applied dicamba may still provide substantial control of some DR kochia populations. However, it is not advisable to apply dicamba alone for PRE kochia control.

The distinction between count nouns and mass nouns affects thinking and writing about various types of crops and produce. Count nouns are words that indicate discrete, countable objects (e.g., forks, viewpoints), whereas mass nouns are words that indicate some relatively undifferentiated substance (e.g., water, energy). We explain the grammar of these two forms and point out some writing pitfalls to avoid. The word seed is one of the few English nouns that is both a count noun and a mass noun. An argument is presented for using seeds as the plural when several individuals are counted and for using seed as the singular when referring to seeds in the aggregate.

Glyphosate-resistant (GR) kochia is an increasing management concern in major cropping systems of the northwestern US. In 2014, we investigated four putative GR kochia accessions (designated as ALA, VAL, WIL, DB) collected from sugar beet fields in eastern Oregon and southwestern Idaho to characterize the level of evolved glyphosate resistance and determine the relationship between the 5-enol-pyruvylshikimate-3-phospate synthase (EPSPS) gene copy number and level of glyphosate resistance. The EPSPS gene copy number was used as a molecular marker to detect GR kochia in subsequent surveys in 2015 and 2016. Based on LD50 values from a whole-plant dose-response study, the four putative GR kochia populations were 2.0- to 9.6-fold more resistant to glyphosate than the glyphosate-susceptible (GS) accession. In an in vivo leaf-disk shikimate assay, leaf disks of GS kochia plants treated with 100-μM glyphosate accumulated 2.4- to 4.0-fold higher amounts of shikimate than the GR plants. The four GR accessions had 2.7 to 9.1 relative EPSPS gene copies compared with the GS accession (<1 EPSPS gene copies), and there was a linear relationship between EPSPS gene copy number and glyphosate resistance level (LD50 values). The 2015 and 2016 GR kochia survey results indicated that about half of the collected populations from sugar beet fields in eastern Oregon had developed resistance to glyphosate whereas only one population from the Idaho collection was confirmed glyphosate resistant. This is the first confirmation of GR kochia in sugar beet fields in eastern Oregon and southwestern Idaho. Diversified weed control programs will be required to prevent further development and spread of GR kochia in sugar beet-based rotations in this region.