ABSTRACT: Herbicide promotes physiological and biochemical changes even in tolerant species. The objective of this study was to evaluate the interference of the herbicides clodinafop-propargyl and 2,4-D in the antioxidant system of wheat, and iodosulfuron-methyl in wheat and ryegrass. Two studies, divided into three experiments, were conducted in an entirely randomized design in a greenhouse and phytotron. The first study tested herbicides iodosulfuron-methyl, clodinafop-propargyl, 2,4-D, and a control without application in wheat. The second, divided into two experiments with wheat and ryegrass, tested iodosulfuron-methyl doses (0, 1.75, 3.5, and 7.0 g a.i. ha-1). The variables analyzed were the concentrations of chlorophylls a, b, carotenoids, hydrogen peroxide (H2O2), lipid peroxidation (TBARS), electrolyte leakage, and antioxidant system activity. The herbicide treatments iodosulfuron-methyl, clodinafop-propargyl, and 2,4-D decreased the concentrations of chlorophylls and carotenoids in wheat plants. The herbicides promoted oxidative stress with increased H2O2 and TBARS concentrations. Increasing the dose of iodosulfuron-methyl provided a reduction in the activity of the enzymatic antioxidant system in wheat and ryegrass. ABSTRACT species clodinafoppropargyl clodinafop propargyl 2,4D 24D D 2,4 2 4 iodosulfuronmethyl iodosulfuron methyl ryegrass studies phytotron iodosulfuronmethyl, methyl, clodinafoppropargyl, propargyl, 2,4D, D, second 0, 0 (0 175 1 75 1.75 35 3 5 3.5 70 7 7. ai i a.i ha1. ha1 ha . ha-1) b H2O2, HO , H O (H2O2) TBARS, (TBARS) leakage plants H2O 4D 24 2, ( 17 1.7 3. ha-1 (H2O2 (TBARS 1. ha- (H2O

RESUMO: A aplicação de herbicidas promove alterações fisiológicas e bioquímicas mesmo nas espécies tolerantes. O objetivo do estudo foi avaliar a interferência dos herbicidas clodinafop-propargyl e 2,4-D no sistema antioxidante do trigo, e iodosulfuron-methyl em trigo e azevém. Dois estudos, divididos em três experimentos, foram conduzidos em delineamento inteiramente casualizado em casa de vegetação e fitotron. O primeiro estudo testou os herbicidas iodosulfuron-methyl, clodinafop-propargyl, 2,4-D, e testemunha sem aplicação em trigo. O segundo, dividido em dois experimentos com trigo e azevém, testou doses de iodosulfuron-methyl doses (0, 1,75, 3,5, and 7,0 g i.a. ha-1). As variáveis analisadas foram as concentrações de clorofilas a, b, carotenoides, peróxido de hidrogênio (H2O2), peroxidação lipídica (TBARS), extravazamento de eletrólitos e atividade do sistema antioxidante. O uso dos herbicidas iodosulfuron-methyl, clodinafop-propagyl e 2,4-D diminuíram o teor de clorofilas e carotenoides nas plantas de trigo. Os herbicidas promovem estresse oxidativo com aumento no teor de H2O2, TBARS e extravasamento de eletrólitos. O aumento da dose do iodosulfuron-methyl proporciona redução da atividade do sistema antioxidante enzimático no trigo e azevém. RESUMO tolerantes clodinafoppropargyl clodinafop propargyl 2,4D 24D D 2,4 2 4 iodosulfuronmethyl iodosulfuron methyl azevém estudos fitotron iodosulfuronmethyl, methyl, clodinafoppropargyl, propargyl, 2,4D, D, segundo 0, 0 (0 175 1 75 1,75 35 3 5 3,5 70 7 7, ia i i.a ha1. ha1 ha . ha-1) b H2O2 HO , H (H2O2) TBARS, (TBARS) clodinafoppropagyl propagyl 4D 24 2, ( 17 1,7 3, ha-1 H2O (H2O2 (TBARS 1, ha- (H2O

RESUMO: A qualidade da água é uma das principais características para uma aplicação eficiente e segura de pesticidas. De maneira geral, a qualidade da água está relacionada aos níveis de pH e dureza. Assim, o objetivo foi avaliar a interação entre o pH da água e tempo de mistura da calda contendo os herbicidas 2,4-D amina, 2,4-D colina e dicamba, na eficácia visível em Ipomoea triloba, Bidens pilosa, Amaranthus viridis; além dos níveis de dureza da água em I. triloba. Três estudos feitos em estufa. Estudo 1 em fatorial 3x5 sendo o fator A pH de 2, 6 e 10 e o fator B 0, 2, 6, 24 e 26 horas da mistura até a aplicação. Estudo 2 em fatorial 3x5 para cada herbicida, sendo o fator A pH de 2, 6 e 10 e o fator B 0, 6, 12, 24 e 48 horas da mistura até a aplicação. Estudo 3 em fatorial 3x7 sendo o fator A os herbicidas e o fator B níveis de dureza da água: 0, 65, 125, 250, 500, 750 e 1000 partes por milhão. O pH manteve-se estável nas 48 horas. Entretanto, não interferiu na eficácia de dicamba em I. triloba. Além disso, maior tempo entre o preparo da calda com as formulações de 2,4-D e a aplicação causou redução da eficácia em I. triloba. Ainda, a dureza da água diminuiu o controle sobre I. triloba. O pH não afetou 2,4-D e dicamba sobre as plantas, entretanto, maior tempo de aplicação reduz a eficácia. RESUMO pesticidas geral Assim 2,4D 24D D 2,4 4 amina triloba pilosa viridis I estufa x 3x 0 herbicida 12 65 125 250 500 75 100 milhão mantevese manteve se Entretanto disso Ainda plantas entretanto 4D 25 50 7 5

ABSTRACT: Carrier water quality is one of the main characteristics for an efficient and safe spraying of pesticides. Overall related to the levels of pH and hardness. The objective was to evaluate the interaction between water pH and storage time of the spray, containing 2,4-D amine, 2,4-D choline and dicamba, on the visible efficacy in Ipomoea triloba, Bidens pilosa, Amaranthus viridis; and water hardness on I. triloba. Three studies were carried out in a greenhouse. Study 1 with a 3x5 factorial, which factor A being pH of 2, 6 and 10 and factor B being 0, 2, 6, 24 and 36 hours of application after the mixture. Study 2 was a 3x5 factorial for each herbicide, whith factor A being the levels of pH (2, 6 and 10) and factor B being 0, 6, 12, 24 and 48 hours of application after the mixture. The study 3 is a 3x7 factorial, with factor A being the herbicides and factor B levels of water hardness: 0, 65, 125, 250, 500, 750 and 1000 parts per million. The pH of all solutions remained stable for 48 hours after preparation. However, did not interfere in efficacy of dicamba in I. triloba. Also, longer time between preparing the spray with 2,4-D formulations and application caused reduction efficacy on I. triloba. Also, the level of water hardness decreased control on I. triloba. The pH of carrier water did not affect efficacy of 2,4-D and dicamba on the weeds; however, longer time of the spray application reduce the visible efficacy. ABSTRACT pesticides 2,4D 24D D 2,4 4 amine triloba pilosa viridis I greenhouse x 3x 0 mixture herbicide (2 12 65 125 250 500 75 100 million preparation However Also weeds however 4D ( 25 50 7 5

ABSTRACT: Italian ryegrass (Lolium multiflorum Lam.) is considered one of the main winter cover crops in southern Brazil; however, it is a weed species with a record of being resistant to several herbicides. The settlement of this species in agricultural areas occurs through the seed bank in the soil, and measures that interfere with seed production can assist in its management. The present study evaluated the phytotoxicity, production, and quality of Italian ryegrass seeds through the application of herbicides 2,4-D and saflufenacil at different stages of development. Three trials were conducted, a completely randomized experimental design for the first two and randomized blocks for the third, all with four replications. The treatments were arranged in a 3x3 factorial scheme, in which factor A was composed of the herbicides saflufenacil (35 g a.i. ha-1), 2,4-D (1005 g a.e. ha-1), plus control without application; and factor B consisted of the booting, anthesis, and maturation Italian ryegrass development stages. The phytotoxicity of the herbicides to Italian ryegrass did not exceed 30%, with saflufenacil causing the greatest injury at anthesis. There was a reduction in Italian ryegrass seed yield when herbicides 2,4-D and saflufenacil were applied, and the application of 2,4-D and saflufenacil at anthesis reduced the percentage of full seeds. The number of empty Italian ryegrass seeds was higher when saflufenacil was applied at anthesis. The application of 2,4-D at maturity reduced Italian ryegrass germination and radicle length. From this perspective, these herbicides can help reduce the production and quality of Italian ryegrass seeds. ABSTRACT Lolium Lam. Lam Brazil however soil management 2,4D 24D D 2,4 2 4 conducted third replications x 3x scheme 35 (3 ai i a.i ha1, ha1 ha 1 , ha-1) 1005 (100 ae e a.e booting 30 30% length perspective 4D 24 2, 3 ( ha-1 100 (10 ha- 10 (1

RESUMO: O azevém (Lolium multiflorum Lam.) é considerado uma das principais plantas de cobertura hibernais do sul do Brasil, porém é uma espécie daninha com registro de resistência a diversos herbicidas. O estabelecimento dessa espécie nas áreas agrícolas ocorre através do banco de sementes no solo, sendo que medidas que interfiram na produção de sementes podem auxiliar no seu manejo. O objetivo do presente trabalho foi avaliar a fitotoxicidade, produção e qualidade de sementes de azevém mediante aplicação dos herbicidas 2,4-D e saflufenacil em diferentes estádios de desenvolvimento. Foram realizados três estudos, em delineamento experimental inteiramente casualizado para os dois primeiros, e blocos casualizados para o terceiro, todos com quatro repetições. Os tratamentos foram arranjados em esquema fatorial 3x3, em que o fator A foi composto pelos herbicidas saflufenacil (35 g i.a. ha-1), 2,4-D (1005 g e.a. ha-1), mais testemunha sem aplicação; e o fator B constituiu-se dos estádios de desenvolvimento do azevém emborrachamento, antese e maturação. A fitotoxicidade dos herbicidas ao azevém não superou 30%, sendo que o saflufenacil promoveu maior injúria e no estádio de antese. Ocorreu redução na produtividade de sementes de azevém quando recebeu aplicação dos herbicidas 2,4-D e saflufenacil, sendo que a aplicação em antese de 2,4-D e de saflufenacil reduz o percentual de sementes cheias. O número de sementes vazias de azevém foi maior quando foi aplicado saflufenacil no estádio de antese. A aplicação de 2,4-D em maturação reduziu a germinação e comprimento da radícula de azevém. Nessa perspectiva, estes herbicidas podem auxiliar na redução da produção e qualidade de sementes de azevém. RESUMO Lolium Lam. Lam Brasil solo manejo 2,4D 24D D 2,4 2 4 estudos primeiros terceiro repetições 3x3 x 35 (3 ia i i.a ha1, ha1 ha 1 , ha-1) 1005 (100 ea e.a constituiuse constituiu se emborrachamento 30 30% cheias perspectiva 4D 24 2, 3x 3 ( ha-1 100 (10 ha- 10 (1

Abstract The objective of this work was to evaluate the influence of herbicides 2,4-D and dicamba on the physiological response of chlorophyll a in olive (Olea europaea) seedlings. The following eight rates of the 2,4 D (670 g a.e. ha-1) and dicamba (720 g a.e. ha-1) herbicides were applied: 0, 1.56, 3.13, 6.25, 12, 25, 50, and 100% of the recommended for burndown. The herbicides were applied at 80 cm above the seedlings using a CO2 pressurized back sprayer with a 150 L ha-1 spray volume. Plant gas exchange was measured using a portable infrared gas analyzer. Chlorophyll a fluorescence was evaluated using a portable modulated light fluorometer. The application of both herbicides caused a decrease in the process of CO2 assimilation in the plants, reducing net photosynthesis and stomatal conductance. The 2,4-D herbicide caused the most severe effects on the variables related to chlorophyll a fluorescence. Low values of maximum quantic yield were observed after the application of the herbicides, of which dicamba was the most harmful. Both herbicides damage the photosynthetic apparatus of olive seedlings. 2,4D 24D 2 4 Olea europaea 24 2, 670 (67 ae e a.e ha1 ha 1 720 (72 0 156 56 1.56 313 3 13 3.13 625 6 25 6.25 12 50 100 burndown 8 CO 15 ha- volume analyzer fluorometer plants conductance harmful 4D 67 (6 72 (7 5 1.5 31 3.1 62 6.2 10 ( 7 1. 3. 6.

Resumo O objetivo deste trabalho foi avaliar a influência dos herbicidas 2,4-D e dicamba sobre a resposta fisiológica da clorofila a em mudas de oliveira (Olea europaea). As seguintes oito doses dos herbicidas 2,4-D (670 g a.e. ha-1) e dicamba (720 g a.e. ha-1) foram aplicadas: 0, 1,56, 3,13, 6,25, 12, 25, 50 e 100% das recomendadas para dessecação. Os herbicidas foram aplicados a 80 cm acima das mudas, por meio de um pulverizador costal pressurizado a CO2, com 150 L ha-1 de volume de calda. A troca gasosa das plantas foi medida por meio de um medidor portátil analisador de gases por infravermelho. A fluorescência da clorofila a foi avaliada por meio de um fluorômetro portátil de luz modulada. A aplicação de ambos os herbicidas causou diminuição no processo de assimilação de CO2 pelas plantas, o que reduziu a fotossíntese líquida e a condutância estomática. O herbicida 2,4 D causou os efeitos mais severos nas variáveis relacionadas à fluorescência da clorofila a. Baixos valores de rendimento quântico máximo foram observados após a aplicação dos herbicidas, dos quais o dicamba foi o mais prejudicial. Ambos os herbicidas danificam o aparelho fotossintético das mudas de oliveira. 2,4D 24D 2 4 Olea europaea. europaea . europaea) 670 (67 ae a.e ha1 ha 1 720 (72 aplicadas 0 156 56 1,56 313 3 13 3,13 625 6 25 6,25 12 5 100 dessecação 8 CO 15 ha- calda infravermelho modulada estomática 24 2, prejudicial 4D 67 (6 72 (7 1,5 31 3,1 62 6,2 10 ( 7 1, 3, 6,

ABSTRACT The cultivation of pecan (Carya illinoinensis K. Koch) and olive trees (Olea europaea L.) near pasture and grain cultivation areas in southern Brazil has caused herbicide drift problems. Therefore, the objective of this study was to evaluate the phytotoxic effects of herbicides 2,4-D and dicamba on the growth of pecan and olive tree seedlings. A total of 8 underdoses were used, as follows: 0, 1.56, 3.125, 6.25, 12.0, 25.0, 50.0, and 100% of the recommended doses of herbicides 2,4-D (670 g a.e ha-1) and dicamba (720 g a.e ha-1) for burndown. The applications were carried out in 80 cm-high seedlings with the aid of a CO2 pressurized sprayer with a spray solution volume of 150 L. ha-1. The analyzed variables were phytotoxicity at 7, 14, 21, 30 and 60 days after spray (DAA) and plant height and stem diameter at 30 and 60 DAA. The drift of hormonal herbicides caused damage to the growth of pecan and olive trees, decreasing their stem diameter and height, with the herbicide dicamba showing the greatest damage. In addition, doses above 12.5% of both herbicides resulted in phytotoxicity levels greater than 60%, and doses of 50 and 100% were responsible for leaf senescence. Carya K Koch Olea L problems Therefore 2,4D 24D D 2,4 2 4 used follows 0 156 1 56 1.56 3125 3 125 3.125 625 6 25 6.25 120 12 12.0 250 25.0 500 50.0 100 670 (67 ae e ha1 ha ha-1 720 (72 burndown cmhigh cm high CO 15 ha1. 1. 7 14 21 DAA (DAA addition 5 12.5 60% senescence 4D 24 2, 1.5 312 3.12 62 6.2 12. 25. 50. 10 67 (6 ha- 72 (7 31 3.1 6. ( 3.

RESUMO O cultivo de nogueira-pecã (Carya illinoinensis K. Koch) e oliveira (Olea europaea L.) no Sul do Brasil próximo a áreas de pastagens e de cultivo de grãos tem registrado problemas de deriva de herbicidas. Diante disso, o objetivo do trabalho foi avaliar os efeitos fitotóxicos dos herbicidas 2,4-D e dicamba sob o crescimento de mudas de nogueira-pecã e oliveira. Para isso, utilizaram-se 8 subdoses, sendo elas 0; 1,56; 3,125; 6,25; 12,0; 25,0%; 50,0; e 100% das doses recomendadas para dessecação dos herbicidas 2,4-D (670 g e.a ha-1) e dicamba (720 g i.a ha-1). As aplicações foram realizadas em mudas com 80 cm de altura com auxílio de um pulverizador costal pressurizado a CO2 com volume de calda de 150 L ha-1. As variáveis analisadas foram a fitotoxicidade aos 7, 14, 21, 30 e 60 dias após a aplicação (DAA), estatura de plantas e diâmetro de caule aos 30 e 60 DAA. A deriva de herbicidas hormonais causou danos ao crescimento das plantas de nogueira e oliveira, diminuindo o diâmetro de caule e a estatura das mesmas, sendo o herbicida dicamba o responsável pelos maiores danos. Além disso, doses acima de 12,5% de ambos os herbicidas resultaram em fitotoxicidade superior a 60%, sendo as doses de 50 e 100% responsáveis pela senescência de folhas. nogueirapecã pecã Carya K Koch Olea L. disso 2,4D 24D D 2,4 2 4 isso utilizaramse utilizaram se subdoses 0 1,56 156 1 56 3,125 3125 3 125 6,25 625 6 25 12,0 120 12 25,0% 250 50,0 500 100 670 (67 ea ha1 ha ha-1 720 (72 ia i ha1. . CO 15 1. 7 14 21 DAA, DAA , (DAA) mesmas 5 12,5 60% folhas 4D 24 2, 1,5 3,12 312 6,2 62 12, 25,0 50, 10 67 (6 ha- 72 (7 (DAA 1, 3,1 31 6, 25, ( 3,

RESUMO: O arroz daninho (Oryza sativa L.) é a principal planta daninha do arroz cultivado e, devido à similaridade genética com a cultura, são poucas as alternativas de controle. Uma possibilidade são os sistemas de cultivo, em razão da influência na emergência e sobrevivência da espécie no banco de sementes do solo. Diante disso, o trabalho objetivou avaliar a longevidade e a distribuição das sementes de arroz daninho no perfil do solo, após 22 anos de cultivo, sob diferentes sistemas. Os tratamentos foram arranjados em esquema fatorial, em que o fator A foi composto por três sistemas de cultivo, realizados consecutivamente durante 22 anos, sendo esses: semeadura direta (SD), sistema convencional (SC) e pré-germinado (PG); e, o fator B composto por quatro profundidades de amostragem: 0-2, 2-5, 5-10 e 10-20 cm. As variáveis avaliadas foram: o número de sementes íntegras e deterioradas m-2; e, a porcentagem de viabilidade. Não foi verificado efeito dos sistemas até 5 cm, mas a 5-10 cm SC e PG mostraram maior quantidade de sementes, e PG a 10-20 cm. A SD proporcionou diminuição de sementes íntegras conforme aumentou a profundidade de amostragem, enquanto o sistema PG elimina menos sementes do banco de sementes do solo. Os sistemas SC e PG distribuem sementes viáveis no perfil do solo de 0 a 20 cm de profundidade. Após 22 anos, nos três sistemas de cultivo há sementes de arroz daninho viáveis até 10 cm de profundidade, sendo igual a quantidade de sementes viáveis até cinco centímetros de profundidade.

ABSTRACT: Weedy rice (Oryza sativa L.) is the most problematic weed in rice fields due to the few control management alternatives to control it, because of the genetic similarity with the crop. Different cropping systems (regarding soil preparation before sowing) have been used as options to control the persistence and emergence of the weed seedbank. Therefore, the objective of this study was to evaluate the longevity and vertical distribution of weedy rice seeds in the soil seedbank after 22 years of different rice cropping systems. Data was analyzed as a two-way factorial, with cropping systems carried out for 22 years [no-tillage (NT), conventional tillage (CT), wet direct-seeded (WDS)] as one factor and sampling depth (0-2, 2-5, 5-10 and 10-20 cm) as the other factor. The number of whole and deteriorated seeds per m-2 were assessed, as well as the viability (%). No effect between the systems were detected up to 5 cm, however at 5-10 cm CT and WDS showed higher amount of seeds, and WDS at 10-20 cm. As the sampling depth increased, NT showed fewer amount of seeds, while less reduction of the soil seedbank was observed in WDS. CT and WDS spread viable seeds in the soil profile from 0 to 20 cm depth. After 22 years there are viable weedy rice seeds up to 10 cm of depth in the three cropping systems and there is no difference among them up to 5 cm of depth, demonstrating the serious problem of the seedbank for this species.

Resumo O objetivo deste trabalho foi avaliar a seletividade de herbicidas pré e pós-emergentes e a sua eficiência no controle de plantas daninhas, bem como o crescimento e a qualidade de hastes florais, na cultura do gladíolo (Gladiolus x grandiflorus), em duas épocas de cultivo. Os experimentos foram conduzidos a campo, onde os gladíolos plantados receberam a aplicação de herbicidas pré e pós-emergentes, com e sem controle mecânico das plantas daninhas. Aos 7, 14, 21 e 28 dias após a emergência (DAE), avaliaram-se o controle de monocotiledôneas e eudicotiledôneas, além da fitotoxicidade no gladíolo. Aos 28 DAE, também foi avaliada a massa seca da parte aérea das plantas daninhas e dos gladíolos. Os herbicidas pré-emergentes s-metolacloro e diuron e o pós-emergente haloxifope-p-metílico são seletivos ao gladíolo, em ambas as épocas de cultivo, o que possibilita a produção de hastes florais com qualidade comercial. Os herbicidas s-metolacloro e haloxifope-p-metílico também promovem controle eficiente de monocotiledôneas independentemente da época de cultivo. Embora, quando aplicados, saflufenacil e 2,4-D causem fitotoxicidade na fase vegetativa do gladíolo, não afetam a produção de hastes florais e controlam satisfatoriamente as eudicotiledôneas no segundo cultivo. pósemergentes pós emergentes Gladiolus grandiflorus, grandiflorus , grandiflorus) cultivo campo pósemergentes, emergentes, 7 14 2 DAE (DAE) avaliaramse avaliaram se préemergentes smetolacloro s metolacloro pósemergente emergente haloxifopepmetílico haloxifope p metílico comercial Embora aplicados 2,4D 24D D 2,4 4 1 (DAE 4D 24 2,

Abstract The objective of this work was to evaluate the selectivity of pre- and post-emergent herbicides and their efficiency in weed control, as well as the growth and quality of floral stems, in a gladiolus (Gladiolus x grandiflorus) crop in two growing seasons. The experiments were carried out in the field, where the planted gladiolus received the application of pre- and post-emergent herbicides, with and without mechanical weed control. At 7, 14, 21, and 28 days after emergence (DAE), monocotyledon and eudicotyledon control and phytotoxicity to gladiolus plants were evaluated. At 28 DAE, the shoot dry matter of weeds and gladiolus plants was also evaluated. The s-metolachlor and diuron pre-emergent herbicides and the haloxyfop-p-methyl post-emergent herbicide are selective to gladiolus plants in both seasons, which allows of the production of floral stems with commercial quality. The s-metolachlor and haloxyfop-p-methyl herbicides also promote an efficient control of monocotyledons regardless of the growing season. Although, when applied, saflufenacil and 2,4-D cause phytotoxicity in the vegetative phase of gladiolus, they do not affect the production of floral stems and control satisfactorily eudicotyledons in the second season. pre postemergent post emergent Gladiolus grandiflorus seasons field 7 14 21 2 DAE , (DAE) evaluated smetolachlor s metolachlor preemergent haloxyfoppmethyl haloxyfop p methyl season Although applied 2,4D 24D D 2,4 4 1 (DAE 4D 24 2,

ABSTRACT The use of auxin mimics herbicides in agriculture is widespread in a great diversity of crops. The indiscriminate use of herbicides can cause adverse effects in the plants. Among the plant species that stand out for being highly competitive and resistant to biotic and abiotic stresses, it is the brazilian peppertree (Schinus terebinthifolius Raddi.). The objective of this work was to evaluate the phytotoxic and photosynthetic alteration effects of different rates simulating the drift of the herbicides 2,4-D and Dicamba in brazilian peppertree seedlings. The experiment was carried out in a completely randomized design with four replications. The treatments were arranged in 2 x 8 factorial design (herbicide x doses). The factor herbicide consisted the herbicides 2,4-D and Dicamba, and, the factor doses eight percentages of the herbicide applied. Phytotoxicity and alteration of photosynthetic and fluorescence of chlorophyll a parameters were evaluated. Increased rate of the 2,4-D and Dicamba cause phytotoxicity to the plants, whose Dicamba promotes greater injuries. Dicamba was the herbicide that caused the greatest damage to the photosynthetic apparatus on brazilian peppertree plants, while for 2,4-D the plants showed higher recovery potential after herbicidal exposure.

Abstract Background The presence of weeds in Roundup Ready® (RR) soybean and corn crops compromises yield. Management practices recommended by the consultants and adopted by producers directly interfere in the occurrence of these species. Objective To survey management practices used in RR soybean and corn fields in the Rio Grande do Sul. Methods Data were gathered via the application of questionnaires during the 2018/19 growing season to consultants working with RR soybean and corn cropping in Rio Grande do Sul state. There were 112 responses, covering about 72 municipalities in the state. Results Technical consultants highlighted Conyza spp. and Lolium multiflorum as the most common weed species and classified resistance to herbicides and advanced stages of weeds at the time of herbicide application as the primary causes of low weed control efficacy. They observed an increase in resistance evolution and a two to three-fold increase in the use of herbicides in glyphosate-tolerant crops. Using a mixture of herbicides was the main recommendation for the management of weeds that escape control, while in areas with proven resistance, crop rotation was the main recommendation. Conclusions Crop rotation and herbicide mixtures are the most recommended management practices, with herbicide resistance and advanced stage of development listed as the main reasons for the difficulties of weed control.

RESUMEN La eficiencia de absorción, translocación y control satisfactorio de malezas pueden ser afectados por el lugar de aplicación del herbicida. Sin embargo, durante la recolección de cultivos previos a la soya, el corte realizado por la cosechadora en la yerba carnicera dificulta el manejo de cultivos en pre-siembra al limitar el área foliar de absorción. Se realizaron experimentos para evaluar la eficiencia del control y el potencial de translocación de saflufenacil en plantas de yerba carnicera en diferentes condiciones. El primer experimento se organizó en esquema factorial 2x10. El factor A corresponde a la integridad de la hoja y el factor B corresponde a los diferentes niveles de daño y aplicación de saflufenacil. El control de Conyza se evaluó a los 7, 14 y 21 días después del tratamiento herbicida (DAT), y el peso seco a los 21 DAT. El experimento II consistió en aplicar saflufenacil a diferentes estructuras de Conyza, donde se evaluó el porcentaje de área necrótica a 1, 3, 5 y 7 DAT. El control de Conyza obtenido fue superior al 75% en todos tratamientos usando saflufenacil, con mayor control en plantas previamente defoliadas. La aplicación de saflufenacil en plantas de 10 y 20 cm fue eficaz en todos los tratamientos. Además, saflufenacil aplicado en el tallo viejo mostró un área necrótica mayor, mientras la aplicación en el sitio del corte generó como resultado un área menos necrótica. La translocación de saflufenacil se da através del xilema y el tallo demostrando ser el elemento a través del cual se da la absorción del herbicida.

ABSTRACT Efficient herbicide absorption and translocation, and satisfactory weed control can be affected by the site of herbicide application. However, during harvesting of crops of previous soybean sowing, the cutting process made by harvesters on the fleabane may generate a difficult management in pre-sowing of the crop by limiting the leaf area of the absorption of the herbicide. Experiments were conducted to evaluate the control efficiency and translocation potential of saflufenacil in fleabane plants with different leaf and stem conditions. Experiment I was arranged in a 2x10 factorial scheme, with factor A corresponding to leaf integrity, and factor B corresponding to different levels of injury and saflufenacil application. Weed control was evaluated at 7, 14, and 21 days after herbicide treatment (DAT), and dry matter was evaluated at 21 DAT. Experiment II consisted of applying saflufenacil to different fleabane structures, where the percentage of necrotic area was evaluated at 1, 3, 5, and 7 DAT. Fleabane control was higher than 75% in all treatments with saflufenacil application, with greater control in plants previously defoliated. Saflufenacil application on 10 and 20 cm hairy fleabane plants was also efficient in all treatments. Saflufenacil application in old stem showed a larger necrotic area, while application in the site of the cutting resulted in a lower necrotic area. The main pathway for translocation of saflufenacil is via xylem and the stem proved to be the absorption element of the herbicide when leaf area is limited.

Abstract Background: Rice fields in the state of Rio Grande do Sul (RS) are one of the largest areas where the herbicide resistant system is utilized worldwide. Weed management is important to achieve high rice yields, and herbicide resistance is the main limiting factor. Knowledge of practices used by farmers is important to understand the dynamics of weeds in rice fields. Objective: To evaluate the frequency of utilization of weed management practices and the main consequences related to herbicide resistance associated with the utilization of the imidazolinone-herbicide resistant rice in RS. Methods: The study was carried out during the 2017/2018 season based on a survey of 103 consultants about weed management in the Clearfield® flooded rice system. Data were analyzed by non-metric multidimensional scaling (NMDS) and word cloud analysis. Results: The main weeds in Clearfield® rice are weedy rice and barnyardgrass, with Cyperus sp. also mentioned. Currently the main reasons for low weed control efficacy are resistance to herbicides, delay in beginning the flooding and application to plants at advanced developmental stages. The consultants’ perceptions indicate that the number of cases of herbicide resistance and area are increasing to several weed species and herbicide modes of action. The predominant rice establishment system is minimum tillage. Conclusions: Barnyardgrass and weedy rice are still a problem after 15 years of utilization of the imidazolinone-herbicide resistance system, and the adoption of best herbicide practices and integrated weed management is necessary in the rice crop in RS.

Abstract Background Weed competition is one of the main constraints to rice yield. Objective Determine the period prior to interference (PPI) of barnyardgrass ( Echinochloa spp.) on the irrigated rice crop as a function of the application of the herbicide cyhalofop-butyl alone and associated with penoxsulam. Methods A field experiment was carried out in a randomized block design, with four replications. The treatments were arranged in a 2×7 factorial scheme, with factor A consisting of the herbicides cyhalofop-butyl and the mixture penoxsulam + cyhalofop-butyl, while factor B consisted of seven coexistence periods: 0, 7, 14, 21, 28, 35, and 120 days after rice emergence (DAE). The herbicides were applied in each of these periods. The analyzed variables were crop height and shoot dry mass of the rice and barnyardgrass, number of grains per panicle, thousand-grain weight, and yield. Results The presence of barnyardgrass competing for environmental resources negatively affected the analyzed variables and rice yield for all periods with a coexistence longer than 28 DAE. Barnyardgrass competition during the entire rice cycle (120 DAE) reduced the shoot dry mass of the crop. Conclusions The PPI termination was determined at 14 DAE for the mixture cyhalofop-butyl + penoxsulam and 29 DAE for cyhalofop-butyl alone.

Abstract Background Achieving satisfactory weed control levels in black oat (Avena strigosa) fields is often difficult, owing to the limited number of registered herbicide molecules. Objective To determine novel options for selective, post-emergence chemical weed control in this crop. Methods Eight herbicide treatments were sprayed in the field onto black oat plants at the tillering stage to evaluate crop safety and control of Conyza spp. and Gamochaeta americana, two major weeds of Brazilian black oats. A separate trial was conducted to further assess herbicide safety in a controlled-environment setting, and mesotrione selectivity was then re-evaluated separately in the greenhouse during the following growing season. Crop phytotoxicity was determined using biomass production both in the field and in greenhouse trials. Results Mesotrione, bentazon, 2,4-D, and a 2,4-D+bentazon tank-mix produced light symptoms of crop phytotoxicity, from which plants quickly recovered. Conyza spp. control was achieved via applications of mesotrione (192 g a.i. ha-1), metsulfuron-methyl (3.9 g a.i. ha-1), and a 2,4-D + bentazon tank-mix (502.5 g a.e. ha-1 + 720 g a.i. ha-1, respectively), whereas proper G. americana control was only achieved via applications of either mesotrione or metsulfuron-methyl. Biomass accumulation by black oat plants in the greenhouse was similar across mesotrione-treated and untreated plants. Conclusions Mesotrione could become an option for selective, post-emergence weed control in black oat fields, aiding in the fight against multiple herbicide-resistant Conyza spp. populations which are widespread across major black oat-growing areas in Brazil.

Abstract Background: The evaluation of selective herbicides for weed control in winter cereals is extremely important. Simple methods to evaluate alterations caused by herbicides in the growth and development of winter cereals can be performed with vegetation indices. Objective: Evaluate the potential of different vegetation indices by optical sensors to detect phytotoxicity caused by herbicides in winter cereals. Methods: The experiment was conducted under field conditions, in a randomized block design with four replications. Herbicides were sprayed when the plants were at Z24. The phytotoxicity was evaluated at 7, 14 and 21 days after treatment (DAT) and the normalized difference vegetation index (NDVI) and the normalized difference red edge index (NDRE) at 16, 22 and 37 DAT. Results: The herbicide 2,4-D was less phytotoxic to winter cereals, while metribuzin and saflufenacil caused higher percentages (up to 50%) of visible injuries. The NDRE discriminated more precisely than NDVI the variations in winter cereals, showing alteration in the chlorophyll content due to the phytotoxicity caused by the herbicides. The canonical correlation analysis found an inverse relationship between phytotoxicity and vegetation indices. Conclusions: The winter cereals studied were tolerant to herbicides, enabling the recovery of growth and development. The NDRE index was the most sensitive and showed greater potential in identifying injuries caused by herbicides. The canonical correlation analysis confirmed the inverse relationship between phytotoxicity and the reduction of vegetation indices.

Resumo: O objetivo deste trabalho foi caracterizar o crescimento e o desenvolvimento da buva (Conyza bonariensis) em razão do acúmulo térmico e do fotoperíodo, em diferentes épocas de semeadura, e propor uma escala para representar os principais estádios de desenvolvimento das plantas. O experimento foi realizado com dez repetições, no período de cultivo 2011/2012. As datas de semeaduras foram: 31/05/2011, 04/07/2011, 03/08/2011, 09/09/2011 e 07/11/2011. A altura de planta (cm) e a fenologia foram avaliadas semanalmente. A duração dos diferentes estádios (dias) e a soma térmica acumulada (°C dia) foram determinadas. A regressão linear mostrou que a altura de plantas relacionou-se à soma térmica acumulada. Independentemente da data de semeadura, a fase vegetativa teve maior duração (em dias e em ºC dia) do que a fase reprodutiva. A semeadura em 07/11/2011 promoveu o encurtamento da fase vegetativa, e o estádio roseta não ocorreu. Houve indução do florescimento em fotoperíodo entre 12,5 e 13,5 horas de luz, independentemente da época de semeadura. Observou-se crescimento mais lento na condição de menor temperatura, em que as plantas acumularam 30,9 e 16,3 °C dia por centímetro de altura, nas semeaduras em 31/05/2011 e 07/11/2011, respectivamente. A escala fenológica prevê adequadamente as fases de desenvolvimento da buva.

Abstract: The objective of this work was to characterize the growth and development of hairy fleabane (Conyza bonariensis) according to thermal accumulation and photoperiod, at different sowing times, and to propose a scale representing the main plant development stages. The experiment was carried out with ten replicates in the 2011/2012 growing season. The sowing dates were: 05/31/2011, 07/04/2011, 08/03/2011, 09/09/2011, and 11/07/2011. Plant height (cm) and phenology were evaluated weekly. The duration of the different stages (days) and thermal time accumulation (°C day) were determined. The linear regression analysis showed that plant height was related to thermal time accumulation. Regardless of the sowing date, the vegetative stage had a longer duration (in days and in ºC day) than the reproductive stage. Sowing on 11/07/2011 promoted the shortening of the vegetative stage, and the rosette stage did not occur. Flowering was induced in the photoperiod between 12.5 and 13.5 hours of light, regardless of the sowing date. Slow growth was observed at lower temperature conditions, when plants accumulated 30.9 and 16.3°C day per centimeter of height for the 05/31/2011 and 11/07/2011 sowing dates, respectively. The phenology scale adequately predicts the development stages of hairy fleabane.