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Abstract The herbicide mixture diclosulam + halauxifen appears to be an alternative for the control of Conyza spp.; however, the spray volume may result in different spray deposition effects on the target and, therefore, on the control. Therefore, the objective of this study was to evaluate the impact of different spray volumes of diclosulam + halauxifen on the control of and damage to the leaf surface of Conyza spp. The experiment was conducted in the field in a randomized block design with four replications. Diclosulam + halauxifen (23.52 g ai ha-1 + 6.32 g ae ha-1) was applied to Conyza spp. at average heights greater than 10 cm, followed by sequential application of glufosinate ammonium (500 g ai ha-1) after 14 days. Different spray volumes (200, 150, 100, 80 and 50 L ha-1) were used. The percentage of droplet coverage was evaluated using hydrosensitive paper and analyzed using DropScan software. After 24 hours of initial application, the leaves were collected for scanning electron microscopy (SEM). Although the different spray volumes did not affect the control, faster necrosis effects were observed at 150 and 200 L ha-1. Moreover, the trichome and stomatal density decreased at a spray volume of 200 L ha-1, indicating greater initial damage at this spray volume. Thus, increased spray spray volumes result in increased spray spray deposition, damage to leaf structures and consequently increased control speed. Resumo O herbicida diclosulam + halauxifen parece ser uma alternativa para o controle de Conyza spp.; no entanto, o volume de pulverização pode resultar em diferentes efeitos de deposição do spray no alvo e, portanto, no controle. Portanto, o objetivo deste estudo foi avaliar o impacto de diferentes volumes de pulverização de diclosulam + halauxifen no controle e danos à superfície foliar de Conyza spp. O experimento foi conduzido a campo em um delineamento de blocos ao acaso com quatro repetições. Diclosulam + halauxifen (23.52 g ia ha-1 + 6.32 g ea ha-1) foi aplicado em Conyza spp. em alturas médias maiores que 10 cm, seguido de aplicação sequencial de glufosinato de amônio (500 g ia ha-1) após 14 dias. Foram utilizados diferentes volumes de pulverização (200, 150, 100, 80 e 50 L ha-1). A porcentagem de cobertura de gotículas foi avaliada usando papel hidrossensível e analisada usando o software DropScan. Após 24 horas da aplicação inicial, as folhas foram coletadas para microscopia eletrônica de varredura (MEV). Embora os diferentes volumes de pulverização não tenham afetado o controle, foram observados efeitos de necrose mais rápidos em 150 e 200 L ha-1. Além disso, a densidade de tricomas e estômatos diminuiu em um volume de pulverização de 200 L ha-1, indicando maior dano inicial neste volume de pulverização. Assim, o aumento dos volumes de pulverização resulta em aumento da deposição de spray, danos às estruturas foliares e, consequentemente, aumento da velocidade de controle.

Abstract The pre-plant burndown of Conyza spp. is a fundamental practice to mitigate weed competition with soybean. However, in light of reports of biotypes resistant to 2,4-D, the search for new options of post-emergent herbicides becomes essential. The objective of the present study was to evaluate the effect of post-emergent herbicides on the leaf structure and chemical control of Conyza spp. with heights greater than 10 cm in soybean pre-plant desiccation. A field experiment was conducted following a randomized block design, with seven treatments and four replicates. For the control data, only mesotrione + atrazine and chlorimuron resulted in control percentages lower than 80%. Regarding scanning electron microscopy (SEM), trichomes were denser on the adaxial leaf surface, while stomata predominated on the abaxial side, though both were present on both surfaces. Their distribution showed tendencies of clustering and randomness, with no consistent pattern linked to the treatments. Slight, non-significant variations in trichome density occurred, especially with halauxifen + diclosulam. The control and halauxifen + diclosulam treatments exhibited higher trichome intensity and less structural damage, whereas fluroxypyr + clethodim, dicamba, and triclopyr resulted in lower intensity and trichome disruption. Consequently, fluroxypyr + clethodim, triclopyr, dicamba, and halauxifen + diclosulam were effective in desiccating Conyza spp., with the first two causing trichome damage via plasmolysis. Resumo A dessecação pré-plantio de Conyza spp. é uma prática fundamental para mitigar a competição de plantas daninhas com a soja. No entanto, diante de relatos de biótipos resistentes ao 2,4-D, a busca por novas opções de herbicidas pós-emergentes torna-se essencial. O objetivo do presente estudo foi avaliar o efeito de herbicidas pós-emergentes na estrutura foliar e no controle químico de Conyza spp. com altura superior a 10 cm na dessecação pré-plantio da soja. Foi conduzido um experimento em campo com delineamento em blocos casualizados, com sete tratamentos e quatro repetições. Nos dados de controle, apenas mesotriona + atrazina e clorimuron resultaram em percentuais de controle inferiores a 80%. Quanto à microscopia eletrônica de varredura (MEV), os tricomas apresentaram maior densidade na superfície adaxial da folha, enquanto os estômatos predominaram na face abaxial, embora ambos estivessem presentes em ambas as superfícies. A distribuição mostrou tendências de agrupamento e aleatoriedade, sem padrão consistente associado aos tratamentos. Ocorreram variações leves e não significativas na densidade de tricomas, especialmente com halauxifen + diclosulam. Os tratamentos controle e halauxifen + diclosulam exibiram maior intensidade de tricomas e menos danos estruturais, enquanto fluroxipir + clethodim, dicamba e triclopyr resultaram em menor intensidade e interrupção dos tricomas. Consequentemente, fluroxipir + clethodim, triclopyr, dicamba e halauxifen + diclosulam foram eficazes na dessecação de Conyza spp., com os dois primeiros causando danos aos tricomas via plasmólise.

The study was to identify the potential tolerance of Crotalaria juncea to diclosulam uptake and translocation and its effects on the physiological metabolism of plants. Two experiments were carried out; I—Evaluation of uptake and translocation of 14C-diclosulam (35 g a.i. ha−1) in C. juncea, at seven and 14 days after emergence. II—Evaluation of chlorophyll a transient fluorescence of dark-adapted C. juncea leaves when applied diclosulam in pre-emergence. Plants of C. juncea presented an anatomical/metabolic barrier to diclosulam translocation in the stem, which may confer tolerance to this herbicidal, besides reduced translocation due to low accumulation in the cotyledons. In addition, plants can maintain photosynthetic metabolism active when growing in soil with diclosulam by not changing the dynamics of energy dissipation. Thus, when cultivated in soil with residual of diclosulam, C. juncea can tolerate the herbicide to maintain plant growth.

Sicklepod is one of the most difficult to control weeds in peanut production in the southeastern United States due to its extended emergence pattern and limited effective herbicides for control. Growers rely on preemergence herbicides as the foundation of their weed control programs; however, postemergence herbicides are often needed for season-long weed control. The objectives of this study were to evaluate the effect of planting pattern and herbicide combinations for sicklepod control in peanut crops. Due to rapid canopy closure, twin-row planting improved late-season sicklepod control by 13% and peanut yield by 5% compared with a single-row pattern. A preemergence application of fluridone, flumioxazin, or fluridone + flumioxazin provided 76% to 89% control of sicklepod 28 d after preemergence. Regardless of the herbicide applied preemergence, paraquat + bentazon + S-metolachlor applied early postemergence was required to achieve ≥90% sicklepod control 28 d after early postemergence. All preemergence herbicide treatments followed by (fb) S-metolachlor or diclosulam + S-metolachlor applied early postemergence provided <90% control 28 d after early postemergence. A mid-postemergence application of imazapic + dimethenamid-P + 2,4-DB controlled sicklepod by 67% to 79% prior to peanut harvest, and biomass reduction was unacceptable (<80%), resulting in difficulty in peanut digging. The highest peanut yield was observed when paraquat + bentazon + S-metolachlor was applied early postemergence fb imazapic + dimethenamid-P + 2,4-DB applied mid-postemergence. Based on the results of this study, a herbicide combination of paraquat + bentazon + S-metolachlor is an important early-season tool for controlling sicklepod in peanut crops. The results also showed that a twin-row planting pattern improved late-season sicklepod control but did not reduce herbicide input to protect peanut yield. Nomenclature: Bentazon; diclosulam; dimethenamid-P; fluridone; flumioxazin; imazapic; paraquat; S-metolachlor; 2,4-DB; sickelpod; Senna obtusifolia L.; peanut; Arachis hypogaea L.

Benghal dayflower and sicklepod are weeds of economic importance in peanut in the southeastern United States due to their extended emergence pattern and limited effective herbicides for control. Field studies were conducted near Jay, Florida, in 2022 and 2023, to evaluate the effect of planting date and herbicide combinations on Benghal dayflower and sicklepod control in peanut crops. Peanut planted in June was exposed to a higher Benghal dayflower density than peanut planted in May. Sicklepod density was similar between May and June planting dates at 28 d after preemergence and early postemergence herbicide applications, but density was greater in peanut that was planted in June, 28 d after the mid-postemergence application. A preemeergence herbicide application followed by (fb) an early postemergence application of S-metolachlor or diclosulam + S-metolachlor controlled Benghal dayflower 84% to 93% 28 d after early postemergence in peanut that was planted in May, but control was reduced to 58% to 78% in the crop that had been planted in June. Regardless of planting date, a preemeergence application fb S-metolachlor or diclosulam + S-metolachlor applied early postemergence provided <80% sicklepod control 28 d after early postemergence. Imazapic + dimethenamid-P + 2,4-DB applied postemergence improved Benghal dayflower control to at least 94% 28 d after mid-postemergence, but sicklepod control was not >85%. Regardless of the planting date, paraquat + bentazon + S-metolachlor applied early postemergence was required to achieve ≥95% sicklepod control. However, herbicide combinations that included paraquat + bentazon + S-metolachlor reduced peanut yield when planting was delayed to June. In fields that are infested with Benghal dayflower and sicklepod, it is recommended that peanut be planted in early May to minimize the potential impact of these weeds and to increase peanut yield. Late-planted peanut required more intensive herbicide applications to obtain the same peanut yield as the May-planted peanut. Nomenclature: Bentazon; diclosulam; dimethenamid-P; fluridone; flumioxazin; imazapic; paraquat; S-metolachlor; 2; 4-DB; Benghal dayflower; sickelpod; Senna obtusifolia (L.) H.S. Irwin & Barneby; Commelina benghalensis L.; peanut; Arachis hypogaea L.

Trifludimoxazin is a new herbicide that inhibits protoporphyrinogen oxidase and is being evaluated for the control of small-seeded annual broadleaf weeds and grasses in several crops. Currently, no information is available regarding peanut cultivar response to trifludimoxazin and its utility in peanut weed control systems. Three unique field experiments were conducted and replicated in time from 2019 through 2022 to determine the response of seven peanut cultivars (‘AU-NPL 17’, ‘FloRun 331’, ‘GA-06G’, ‘GA-16HO’, ‘GA-18RU’, ‘GA-20VHO’, and ‘TifNV High O/L’) to preemergence applications of trifludimoxazin and to determine the efficacy of trifludimoxazin at multiple rates and tank-mixtures with acetochlor, diclosulam, dimethenamid-P, pendimethalin, and S-metolachlor for weed management. Cultivar sensitivities to trifludimoxazin were not observed. Peanut density was not reduced by any trifludimoxazin rate. Compared with nontreated controls, in 2019 when trifludimoxazin was applied at 75 g ai ha–1, leaf necrosis increased by 18% and peanut stunting increased by 10%, and yield was reduced by 6%. However, this rate increased leaf necrosis by only 4%, stunting by 3% to 5%, and it had no negative effect on yield in 2020–2021. Generally, peanut injury from preemergence-applied trifludimoxazin was similar to or less than that observed from flumioxazin at 2 wk after application (WAA). Peanut yield in the weed control study was reduced by 11% to 12% when treated with trifludimoxazin at 150 g ha–1 (4× the standard rate) when compared to the 75 g ha–1 rate. However, yield was not different from the flumioxazin treatment. Palmer amaranth control with trifludimoxazin combinations was ≥91% at 13 WAA, wild radish control was ≥96% at 5 WAA, and annual grass control was ≥97% at 13 WAA. Peanut is sufficiently tolerant of 38 g ha–1 of trifludimoxazin, and when tank-mixed with other residual herbicides provides weed control similar to flumioxazin-based systems. Nomenclature: Acetochlor; diclosulam; dimethenamid-P; flumioxazin; pendimethalin; S-metolachlor; trifludimoxazin; Palmer amaranth; Amaranthus palmeri S. Watson AMAPA; wild radish; Raphanus raphanistrum L. RAPRA; peanut; Arachis hypogaea L.

Pink purslane is often ranked as one of the most troublesome weeds in vegetable production systems in Georgia. Pink purslane encroachment along field edges and in-field of agronomic crops has recently increased. Postemergence herbicides are an effective component of agronomic crop weed management. However, little research has addressed pink purslane control in agronomic crops. Therefore, greenhouse and field studies were conducted from 2022 to 2023 in Tifton, Georgia, to evaluate the response of pink purslane to postemergence herbicides commonly used in agronomic crops. Greenhouse screening provided preliminary evidence whereby 13 of the 21 postemergence herbicides evaluated provided ≥80% aboveground biomass reductions. These 13 herbicides were then used for field studies. Results from the field studies, pooled across two locations, indicated that only three of the 13 herbicides provided aboveground biomass reductions of ≥70% compared to the nontreated control. Those herbicides included atrazine at 1,682 g ai ha–1, glufosinate at 656 g ai ha–1, and lactofen at 219 g ai ha–1 with 79%, 70%, and 83% biomass reduction, respectively (P < 0.05). This research suggests that many of the postemergence herbicides used on agronomic crops will not effectively control pink purslane. Thus, when trying to manage pink purslane with postemergence herbicides in agronomic crops, growers should plant crops or cultivars that are tolerant of either atrazine, glufosinate, lactofen, or a combination of these. Nomenclature: Acifluorfen; atrazine; bentazon; carfentrazone; chlorimuron; dicamba; diclosulam; diuron; fomesafen; glyphosate; glufosinate; imazapic; lactofen; mesotrione; paraquat; tembotrione; tolpyralate; topramezone; 2,4-D choline; 2,4-DB; pink purslane, Portulaca pilosa L. PORPI

This study aimed to analyze the efficacy of different pre-emergence active ingredients on the suppression of the weed seed bank and the growth of soybeans. The experiments were carried out on a commercial farm located in Brejo (MA, Brazil), during the 2019/2020 harvest. The experiment was designed in randomized blocks with nine treatments and four replicates. The treatments consisted of control (without pre-emergence application), s-metolachlor, flumioxazin + imazethapyr, flumioxazin, imazethapyr, trifluralin, diclosulam, diclosulam + imazethapyr, and clomazone + carfentrazone-ethyl. Phytosociological surveys were carried out in pre- and post-planting (10 and 36 d after application - DAA) to control weed competition. Nineteen species of weeds were identified, distributed in 17 genera and 13 botanical families. The species Scoparia dulcis, Richardia scabra, and Cyperus iria exhibited the highest phytosociological indices (123.77, 28.62, and 28.29, respectively), estimated at 36 DAA. Flumioxazin and diclosulam were the most efficient in suppressing weed competition, with only 15.63 and 16.13 plants m-2. The highest phytotoxicity scores (3.0) were found at 10 DAA with the application of s-metolachlor, flumioxazin + imazethapyr, trifluralin, and diclosulam + imazethapyr. The pre-emergent control using flumioxazin and diclosulam is recommended for the edaphoclimatic conditions in the Eastern mesoregion of the state of Maranhão, Brazil.

Weed management in peanut primarily relies on intensive herbicide programs. Integrating cereal rye as a cover crop may reduce herbicide input without compromising weed control. Field experiments were conducted to evaluate cereal rye termination management and herbicide programs in peanut. Main plot treatments included a winter fallow control and four cereal rye termination scenarios: 1) early termination 28 d before peanut planting (DBP) with residue rolled flat; 2) early termination 28 DBP with residue left standing; 3) late termination 14 DBP with residue rolled flat; or 4) late termination 14 DBP with residue left standing. Subplot treatments consisted of four herbicide programs: 1) preemergence + early postemergence +mid-postemergence herbicides; 2) preemergence + mid-postemergence herbicides; 3) early postemergence + mid-postemergence herbicides; and 4) a nontreated control. Early cereal rye termination (28 DBP), whether rolled or standing, reduced Palmer amaranth density by 36% to 48% without preemergence herbicides and by 36% to 50% when preemergence herbicides (fluridone or flumioxazin) were applied. Sicklepod density was unaffected by early termination. In contrast, late termination reduced sicklepod density by 47% to 50% and Palmer amaranth density by 64% to 86% relative to the winter fallow control at 28 d after preemergence application. Across all treatments, cereal rye reduced Palmer amaranth and sicklepod biomass by 63% to 67% and 63% to 65%, respectively, 28 d after mid-postemergence herbicides were applied. However, standing cereal rye residue reduced peanut yield compared to rolled residue and the winter fallow. Late-terminated, rolled cereal rye residue combined with reduced herbicide programs (preemergence + mid-postemergence or early postemergence + mid-postemergence) provided weed control and yield comparable to the intensive herbicide program (preemergence + early postemergence + mid-postemergence) in winter fallow control. Based on these findings, late-terminated, rolled cereal rye has the potential to reduce herbicide input while maintaining peanut yield and effective weed suppression. Nomenclature: Acifluorfen; bentazon; diclosulam; dimethenamid-P; fluridone; flumioxazin; imazapic; paraquat; premix bentazon-acifluorfen; S-metolachlor; 2,4-DB; Palmer amaranth; Amaranthus palmeri S. Watson.; sicklepod; Senna obtusifolia (L.) H.S. Irwin & Barneby; cereal rye; Secale cereale L.; peanut; Arachis hypogaea L.

Considering the complexity of using these products, the objective of this work was to evaluate their selectivity and residual weed control in soybean crops and their effect on the weeds Amaranthus hybridus, Bidens pilosa, Digitaria insularis, Eleusine indica, and Euphorbia heterophylla. [...]tolerant soybean cultivars may respond differently to stress caused by herbicides due to genotypic differences (Lima et al., 2011). [...]the selectivity and effectiveness of residual herbicides need to be better understood in current production systems, considering mainly the adopted crop system and the new available soybean cultivars. [...]the objective of the present work was to evaluate the selectivity and residual weed control of pre-emergent herbicides applied before and at the sowing of soybean crops. Weed control at post-emergence of the soybean crops was carried out in the whole area at 15 days after emergence, using glyphosate (Roundup DI®, Monsanto, St. Louis, United States) at 6 L of the commercial product per hectare, clethodim (240 g L-1) (Select 240 EC®; UPL Ltd, Mumbai, India) at 0.45 L of the commercial product per hectare), and the adjuvant (Lanzar®; UPL Ltd, Mumbai, India) 0.5% v v', at a flow rate of200 L ha-1.