Smooth scouringrush has invaded no-till production fields across the US Pacific Northwest. Equisetum species can take up and accumulate silica on the epidermis and in cell walls that may affect herbicide uptake. The objectives of this study were to measure the silica concentration in smooth scouringrush stems over time, and to determine how time of application affects the efficacy of glyphosate for smooth scouringrush control, with and without the addition of an organosilicone surfactant (OSS). Field studies were conducted at three sites in eastern Washington from 2019-2021. Three herbicide treatments (no herbicide, glyphosate, and glyphosate + OSS) were applied at four application times (May, June, July, and August) in 2019 fallow. The silica content of smooth scouringrush stems increased over the course of the 2019 growing season at all three sites. In 2020, smooth scouringrush stem densities were reduced when the 2019 herbicide treatments were applied in late June (12% of no herbicide density) compared to late July (24%) or August (30%). Smooth scouringrush stem densities at all three sites, in both 2020 and 2021, were reduced in the glyphosate + OSS treatment compared to glyphosate alone. In 2021, two years after herbicide application, there was no effect of application timing for the glyphosate treatment without OSS, but stem densities were reduced when glyphosate + OSS was applied in late June (1%) compared with late July (26%) or late August (21%) applications. It is not clear if the cause of reduced glyphosate efficacy with late July and late August applications is the result of increased silica content in smooth scouringrush stems over time. Maximum glyphosate efficacy on smooth scouringrush was achieved with a late-June application and with the addition of an OSS. Control of smooth scouringrush with glyphosate + OSS can be sustained for at least two years after application.

Developing an effective weed management strategy is crucial to sustainable rice production in Nigeria. Rainfed lowland ecology contributes significantly to the volume of rice cultivated in the country in terms of yield and land acreage. Nevertheless, increased weed infestation remains one of its major production constraints. This review highlights the strength and weaknesses of weed management practices in rainfed lowland ecology, potential research gaps, and discusses the potential of a sustainable weed management strategy for lowland rice. In this review, a rainfed lowland situation is described (where water is limited) to engage flooding as a potential weed control option, due to the undulating land terrains. Effective weed management begins with creating a weed-free environment at the critical crop growth stages, such that broadcasted or transplanted rice seedlings can efficiently utilize water, nutrients, and light. Sustainable weed management practices in Nigerian lowland ecology would therefore imply that farmers begin to incorporate crop rotation to suppress problem weed pressure in continuous rice cropping systems, adopt conventional or minimum tillage to enhance herbicide efficacy and early establishment of rice, adopt weed competitive and high yielding cultivars, and practice appropriate spacing, seeding rate, and seeding methods that can support easy adoption of mechanical weeders and optimum plant population to suppress weed pressure at a later growth stage. This is feasible where farmers are supported with infrastructural facilities, farm machinery, and necessary inputs. Future research should engage lowland rice farmers in specific agroecological zones.

Field experiments were conducted in 2020 and 2021 to determine the effectiveness of electrocution on several weeds commonly encountered in Missouri soybean production using an implement known as The Weed Zapper™. In the first study, the effectiveness of electrocution on waterhemp, cocklebur, giant and common ragweed, horseweed, giant and yellow foxtail, and barnyardgrass was determined. Electrocution was applied when plants reached average heights and/or growth stages of 30 cm, 60 cm, flowering, pollination, and seed set. Electrocution was applied once or twice, at two different tractor speeds. Electrocution was more effective at the later plant growth stages. Pearson correlation coefficients indicated that control of weed species was most related to plant height and amount of plant moisture at the time of electrocution. When plants contained seed at the time of electrocution, viability was reduced from 54 to 80% among the species evaluated. A second study determined the effect of electrocution on late-season waterhemp plants, and also soybean injury and yield. Electrocution timings took place throughout reproductive soybean growth stages. The control of waterhemp escapes within the soybean trial ranged from 51 to 97%. Yield of soybean electrocuted at the R4 and R6 growth stages were similar to the non-treated control, but soybean yield was reduced by 11 to 26% following electrocution at all other timings. However, the visual injury and yield loss observed in these experiments likely represents a worst-case scenario as growers that have a clear height differential between waterhemp and the soybean canopy would not need to maintain contact with the soybean canopy. Overall, results from these experiments indicate that electrocution as part of an integrated program could eliminate late-season herbicide-resistant weed escapes in soybean, and reduce the number and viability of weed seed that return to the soil seedbank.

Hair fescue is a perennial grass weed in lowbush blueberry fields that forms dense sods and reduces yield. Growers rely on preemergence (PRE) pronamide applications and postemergence (POST) applications of the group 2 herbicides foramsulfuron and nicosulfuron + rimsulfuron for hair fescue management due to natural tolerance or resistance of this grass to other currently registered herbicides. This causes repeated application of group 2 herbicides, which is compounded by the recent registration of flazasulfuron for POST hair fescue suppression in lowbush blueberry. Mixtures of group 2 herbicides with the amino acid-inhibiting herbicides glyphosate (Group 9) and glufosinate (Group 10), however, can improve weed control and may provide mixtures to delay herbicide resistance development. This research utilized a factorial arrangement of group 2 herbicide (none, foramsulfuron [35 g ai ha-1], nicosulfuron + rimsulfuron [13 + 13 g ai ha-1], flazasulfuron [50 g ai ha-1]) and mixture (none, glyphosate [902 g ae ha-1], and glufosinate [750 g ai ha-1]) to identify possible mixtures that improve weed control and delay resistance development. Herbicides were applied in spring non-bearing year, fall bearing year, and fall non-bearing year, with each application timing conducted as a separate experiment. Foramsulfuron and nicosulfuron + rimsulfuron were not effective as fall applications and spring applications of these herbicides with glyphosate or glufosinate improved hair fescue suppression. Glyphosate and glufosinate were more effective as fall rather than spring applications. Flazasulfuron was effective across all application timings, though mixture with glufosinate generally improved hair fescue suppression. Flazasulfuron + glufosinate is tentatively recommended as an effective mixture for spring non-bearing and fall bearing year hair fescue management in lowbush blueberry.

Control of southern pine species that easily establish from seed, such as loblolly pine and slash pine (wilding pines), has historically been achieved economically through the use of prescribed fire or application of glyphosate or glyphosate and saflufenacil during site preparation. Currently, alternatives to glyphosate are being investigated for wilding pine control due to health and safety concerns over glyphosate reported by some organizations. Two exploratory studies in the Coastal Plain Region of Georgia, USA investigated the potential of several herbicides for wilding pine control with 0.56 to 0.70 kg ha-1 of 0.9 kg ae imazapyr included in all herbicide treatments. Application timings for study one were July and September (n=8 treatments per timing) while study two was July and early November (n=4 treatments per timing). In study one, various rates of choline triclopyr, ester triclopyr, fluroxypyr, aminopyralid + florpyrauxifen-benzyl, and aminopyralid + triclopyr were tested while two treatments contained glyphosate. Study two investigated mixtures containing flumioxazin, glufosinate, and triclopyr. Results for study one revealed that the two treatments containing glyphosate had the greatest percent loblolly pine control after 120 days (87.5% and 88.6% control), while the next best control was offered by a treatment containing imazapyr plus 3.36 kg ha-1 choline triclopyr (52.6% control). July treatments offered better control than September treatments, but efficacy of September treatments may have been impacted by a severe drought. In study two, treatments applied during early November that contained imazapyr and glufosinate or imazapyr, glufosinate, and flumioxazin resulted in 100% control of mixed loblolly and slash pine seedlings and saplings. All November treatments offered better control than July treatments in study two. Promising results from study two suggest that glufosinate may warrant additional study for use in forestry site preparation as an alternative for glyphosate to control wilding pines.

A two-year field experiment was conducted to explore the effects of intercropping sweet corn with summer savory on weed growth and crop productivity. Five cropping patterns were set up: sweet corn alone (16 seeds m-2: in rows, 75cm apart), summer savory alone (40 seeds m-2; broadcasted), and three intercropping ratios of 75% sweet corn, 25% summer savory (75%C: 25%S), 50%C: 50%S and 25%C: 75%S, of plant densities used in respective monocultures. When intercropping, weed biomass decreased as the proportion of summer savory increased with a reduction of 48%, 61% and 70 % in 75%C: 25%S, 50%C: 50%S and 25%C: 75%S, respectively, compared to sweet corn alone. In parallel, sweet corn yield was higher under intercropping compared to its monoculture, and increased as the proportion of summer savory decreased with yield increases compared to corn monoculture of 38%, 32% and 15% in the first year and 48%, 23% and 14 % in the second year in 75%C: 25%S, 50%C: 50%S and 25%C: 75%S, respectively. However, the intercropping pattern had the opposite effect on summer savory yield with a significant reduction in yield with an increasing ratio of sweet corn. Our results indicate that intercropping sweet corn with summer savory can increase both weed suppression and yield of sweet corn compared to crop monoculture.

Three dose-response trials were performed in 2020 and 2021 at two Indiana locations: the Southwest Purdue Agricultural Center (SWPAC) and the Pinney Purdue Agricultural Center (PPAC), to determine the tolerance of two Jack O’Lantern pumpkin cultivars to fomesafen applied preemergence. The experiment was a split-plot arrangement in which the main plot was the fomesafen rate (0, 280, 560, 840, and 1,220 g ai ha−1), and the subplot was the pumpkin cultivar ('Bayhorse Gold’ and 'Carbonado Gold'). As the fomesafen rate increased from 280 to 1,120 g ha−1, the predicted pumpkin emergence decreased from 85 to 25% of the non-treated control at SWPAC-2020, but only from 99 to 74% at both locations in 2021. The severe impact on emergence at SWPAC-2020 was attributed to rainfall. Visible injury included bleaching and chlorosis due to the herbicide splashing from the soil surface onto the leaves and included stunting, but injury was transient. As the fomesafen rate increased from 280 to 1,120 g ha−1, the predicted marketable orange pumpkin yield decreased from 95 to 24% of the non-treated control at SWPAC-2020 and 98 to 74% at PPAC-2021. Similarly, the predicted marketable orange pumpkin fruit number decreased from 94 to 21% at SWPAC-2020 and 98 to 74% at PPAC-2021. Fomesafen rate did not affect marketable orange pumpkin yield and fruit number at SWPAC-2021 and marketable orange pumpkin fruit weight at any location year. Overall, the fomesafen rate of 280 g ha−1 was safe for use preemergence in the pumpkin cultivars 'Bayhorse Gold’ and 'Carbonado Gold’ within one day after planting, but there is a risk of increased crop injury with increasing rainfall.

False-green kyllinga is a problematic C4 perennial Cyperaceae species. Previous research examined herbicide efficacy but has not integrated non-chemical practices with herbicides. Replicate field experiments were conducted to evaluate late summer postemergence applications of herbicides in combination with turf-type tall fescue interseeding for false-green kyllinga control. Seven herbicide treatments and a non-treated control formed a complete factorial with tall fescue interseeding or no seeding (eight-by-two factorial). Six herbicide treatments consisted of single postemergence applications of halosulfuron-methyl (70 g ha−1), imazosulfuron (420 g ha−1), and sulfentrazone + carfentrazone (280 + 30 g ha−1) applied 4 wk before tall fescue interseeding (WBS) and the day of interseeding. Glyphosate (220 g ae ha−1) applied the day of interseeding was the seventh herbicide treatment. Tall fescue was interseeded in September and false-green kyllinga control was evaluated the following summer. In combination with tall fescue interseeding, imazosulfuron and halosulfuron applied 4 WBS as well as glyphosate applied the day of interseeding controlled false-green kyllinga more than all other treatments. In July, imazosulfuron and halosulfuron treatments applied 4 WBS and combined with interseeding had 1 to 6% false-green kyllinga cover, respectively, compared to 28% and 62% cover, respectively, without interseeding. Interseeding alone controlled false-green kyllinga < 50%. Imazosulfuron, halosulfuron, and sulfentrazone + carfentrazone applied the day of seeding severely injured emerging tall fescue seedlings and reduced turfgrass quality the following spring. Applying imazosulfuron or halosulfuron in late summer and interseeding turf-type tall fescue 4 wk later or applying glyphosate the day of seeding are effective strategies for postemergence false-green kyllinga control. Integrating herbicides and the cultural practice of tall fescue interseeding provided more false-green kyllinga control than either practice alone.

Gowan Company recently registered benzobicyclon, a WSSA Group 27 herbicide, as a postflood option in rice. It is the first 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide commercially available in mid-southern U.S. rice production. In 2018 and 2019, field experiments were conducted across multiple sites in Arkansas to determine if the addition of benzobicyclon to quizalofop- or imidazolinone-resistant rice herbicide programs would improve weedy rice control. Across site years, one application of quizalofop, either at the 1- or 3-leaf rice stage, followed by benzobicyclon applied postflood, provided comparable weedy rice control to two sequential applications of quizalofop, which is a standard herbicide program in quizalofop-resistant rice. Additionally, treatments containing quizalofop or quizalofop followed by benzobicyclon injured rice ≤5% at 28 d after the postflood application. Across site years, at 28 d after the postflood application of benzobicyclon, all treatments containing a full-season herbicide program followed by benzobicyclon postflood provided comparable or improved weedy rice control when compared to two sequential early postemergence applications of imazethapyr. In both experiments, rice treated with benzobicyclon yielded comparably or better than treatments containing the standard herbicide program for each system. Findings from this research suggest that the use of benzobicyclon in quizalofop- and imidazolinone-resistant rice systems could be an additional and viable weedy rice control option for rice producers.

The tolerance of cereal rye to eight herbicides registered for use in wheat, at two rates, was evaluated for potential labeling in cereal rye to expand limited chemical weed control options. Across five site-years, halauxifen-methyl plus florasulam, pyroxsulam, and thifensulfuron-methyl plus tribenuron-methyl applied at a 2X rate to cereal rye at Zadoks (Z) 13 caused less than 15% injury, and had no impact on cereal rye density. These herbicides at the 2X rate reduced cereal rye heights 11% at 10 DAT with rye recovering by 31 DAT; cereal rye heights were not reduced with these herbicides at their 1X rate. In contrast, significant injury was observed with the 1X rate of mesosulfuron-methyl (45%), pinoxaden (27%), and pinoxaden plus fenoxaprop-p-ethyl (30%) applied postemergence (POST); early-season height was reduced 19 to 26%. Residual herbicides pyroxasulfone applied as a delayed preemergence (PRE) at Z 10, or flumioxazin plus pyroxasulfone applied at Z 11, caused 27 to 28% and 16 to 47% injury, respectively, when the 1X rate was activated by rainfall within 2 d of application. These residual herbicides reduced cereal rye height and density up to 35 and 40%, respectively. Cereal rye grain yield was not influenced by herbicide or rate applied.

The impacts of training image sizes and optimizers on deep convolutional neural networks for weed detection in alfalfa have not been well explored. In this research, AlexNet, GoogLeNet, VGGNet, and ResNet were trained with various sizes of input images, including 200 × 200, 400 × 400, 600 × 600, and 800 × 800 pixels, and deep learning optimizers including Adagrad, AdaDelta, Adaptive Moment Estimation (Adam) and Stochastic Gradient Descent (SGD). Increasing input image sizes reduced the classification accuracy of all neural networks. The neural networks trained with the input images of 200 × 200 pixels resulted in better classification accuracy than the other image sizes investigated here. The optimizers affected the performance of the neural networks for weed detection. AlexNet and GoogLeNet trained with AdaDelta and SGD outperformed Adagrad and Adam; VGGNet trained with AdaDelta outperformed Adagrad, Adam, and SGD; and ResNet trained with AdaDelta and Adagrad outperformed the Adam and SGD. When the neural networks were trained with the best-performed input image size (200 × 200 pixels) and the deep learning optimizer, VGGNet was the most effective neural network with high precision and recall values (≥0.99) in the validation and testing datasets. At the same time, ResNet was the least effective neural network for classifying images containing weeds. However, the detection accuracy did not differ between broadleaf and grass weeds for the different neural networks studied here. The developed neural networks can be used for scouting weed infestations in alfalfa and further integrated into the machine vision subsystem of smart sprayers for site-specific weed control.

A field experiment was conducted in 2019 and 2020 including a total of six site-years and four locations in Arkansas to determine the optimal sequence and timing of dicamba and glufosinate applications when applied alone, sequentially, or in combination to control Palmer amaranth by size: labeled (<10-cm height) and non-labeled (13- to 25-cm height). Single applications of dicamba, glufosinate, and dicamba plus glufosinate (not labeled) resulted in less than 80% Palmer amaranth control, regardless of weed size. The mixture of dicamba plus glufosinate was antagonistic for Palmer amaranth control and percent mortality. Sequential applications, averaged over all time intervals and herbicides, improved the percentage of Palmer amaranth control 11 to 17 percentage points over a single application, regardless of weed size at application 28 d after final application (DAFA). Palmer amaranth control with glufosinate followed by (fb) glufosinate and dicamba fb dicamba, pending weed size, were optimized at 7-, and 14- to 21-day intervals, respectively. Since single site of action (SOA) postemergence systems increase the likelihood of resistant biotypes and are not a best management practice (BMP) in that regard, sequential applications involving both dicamba and glufosinate were more effective. Further the sequence of application mattered with a preference for applying dicamba first. Dicamba fb glufosinate at a 14-day interval was profit-maximizing and the only herbicide treatment that resulted in 100% weed control when size was <10-cm. For larger weed sizes, economic analysis revealed dicamba fb dicamba to perform better than dicamba fb glufosinate when no penalty was assigned for using a single SOA. This resulted in greater yield loss risk and soil weed seed bank in comparison to timelier weed control with the smaller weed size. Hence timely weed control and two SOA to control Palmer amaranth are recommended as BMPs that reduce producer risk.

Tolpyralate is a herbicide that is usually mixed with atrazine for broad-spectrum weed control in corn. Previous research has provided information on the effective dose (ED) of tolpyralate applied alone and in a 1:33.3 mixture with atrazine; however, tolpyralate is commercially applied at a dose of 30-40 g ai ha-1 with a minimum of 560 g ai ha-1 of atrazine. Therefore, five field trials were conducted over three years (2019-2021) to determine the ED of atrazine to complement 30 g ai ha-1 of tolpyralate for 80, 90, and 95% control of seven weed species 2, 4, and 8 weeks after application (WAA). Tolpyralate was applied alone and in a mixture with atrazine doses ranging from 50-2,000 g ai ha-1. At 8 WAA, the ED of atrazine for 95% control of velvetleaf, common ragweed, common lambsquarters, and wild mustard was below the minimum label dose of atrazine on the commercial tolpyralate label, ranging from 430-520 g ai ha-1, which supports the use of the minimum label dose of atrazine. In contrast, redroot pigweed required 1,231 g ai ha-1 of atrazine to complement tolpyralate for 95% control 8 WAA. At 8 WAA, barnyardgrass and a mixture of green foxtail and giant foxtail (Setaria spp.) were not controlled 80, 90, or 95% with tolpyralate applied alone or co-applied with any dose of atrazine evaluated in this study. The results of this study conclude that tolpyralate + atrazine is highly efficacious on several weed species at atrazine doses of 40-130 g ai ha-1 below the label dose of 560 g ai ha-1, but the use of the higher dose of tolpyralate or another herbicide may be required to improve control of redroot pigweed and grass weed species.