Giliardi Dalazen

A mistura de atrazina + mesotriona exibe sinergismo variável dependendo da dose e da espécie. Este estudo avaliou a eficácia e o potencial sinérgico desta mistura comercial para o controle de buva. Um experimento de dose-resposta em casa de vegetação foi conduzido utilizando um delineamento inteiramente casualizado com quatorze tratamentos e quatro repetições. Atrazina foi aplicada nas doses de 62,5-2000 g i.a. ha-1 isolada e em formulação com mesotriona, além de mesotriona aplicada isoladamente (100 g i.a. ha-1) e uma testemunha sem tratamento. Níveis de controle e redução de biomassa foram avaliados até 35 dias após o tratamento, juntamente com a massa fresca da parte aérea e a massa seca da parte aérea. Posteriormente, foi realizada uma análise de variância (P < 0,05) e regressões logísticas foram ajustadas. O efeito da mistura foi calculado utilizando o método de Colby. Os resultados mostraram que a atrazina isolada exigiu a dose mais elevada para um controle satisfatório (>80%). Por outro lado, a mistura proporcionou controle eficaz e redução de biomassa em 500 g de atrazina + 50 g de mesotriona ha-1. Os valores de C50 da atrazina foram de 897,72 g i.a. ha-1 na aplicação isolada e 130,88 g i.a. ha-1 na mistura com mesotriona aos 35 DAT. O método de Colby confirmou interação sinérgica entre os ingredientes ativos (91% observado vs. 67,9% esperado aos 35 DAT). Consequentemente, a mistura atrazina + mesotriona é recomendada como opção para manejo de buva em pós-emergência.

A resistência de plantas daninhas a herbicidas, especialmente ao glifosato, tem dificultado seu manejo em lavouras de soja. Uma alternativa é o uso de herbicidas pré-emergentes. No entanto, mesmo quando recomendados para a cultura, a seletividade depende de diversos fatores, incluindo a cultivar de soja. Nesse sentido, o objetivo deste trabalho foi avaliar a sensibilidade de diferentes cultivares de soja ao herbicida metribuzin. O experimento foi conduzido em casa de vegetação, em delineamento inteiramente casualizado com quatro repetições, em esquema fatorial 19 x 3. O fator A consistiu em 19 cultivares de soja. O fator B consistiu em três doses de metribuzin: zero, 480 g i.a. ha⁻¹ e 960 g i.a. ha⁻¹. As variáveis avaliadas foram: fitotoxicidade, eficiência quântica do FSII (Fv/Fm), eficiência efetiva do FSII (YII), taxa relativa de transporte de elétrons (rETR), altura da planta e massa seca da parte aérea (MSPA). Os dados foram submetidos à análise de variância (ANOVA) (p < 0,05) e as médias foram comparadas pelo teste de Scott-Knott (p < 0,05). Observou-se interação significativa entre os fatores cultivar de soja e dose de metribuzin. O herbicida metribuzin causou alterações negativas nas características fisiológicas e de crescimento das plantas, demonstrando a fitotoxicidade do herbicida em algumas cultivares de soja, especialmente na maior dose avaliada. As cultivares M 5917, M 6130 I2X, M 6301 I2X e NS 5252 I2X apresentaram maior tolerância ao metribuzin.

O glifosato, herbicida mais utilizado no mundo, é comercializado sob diferentes formulações e sais, que podem alterar o desempenho do herbicida no campo. O objetivo do presente estudo foi verificar a eficiência de cinco diferentes formulações de glifosato na dessecação de Urochloa brizantha BRS "Piatã". Dois experimentos foram conduzidos em dois locais a campo, Alvorada do Sul-PR (Experimento 1) e Londrina-PR (Experimento 2). Cinco formulações de glifosato (sal de isoprapilamina-IPA, sal de di-amônio - Di-NH4+, sal de potássio - K+, sal de NH4+, sal de IPA + K+) foram testadas em duas doses, 900 e 1800 g e.a. ha-1. No experimento 1, a formulação de sal de K+ resultou em efeito mais rápido que as demais. As formulações NH4+ e IPA se mostraram mais lentas, aos 28 dias após a aplicação dos tratamentos. No experimento 2, não houve diferença entre as formulações, somente para as doses. De modo geral, os experimentos demonstraram que a dose de 1800 g e.a. ha-1 foi superior no controle das plantas do que a dose de 900 g e.a. ha-1, o que ressalta a importância do uso da dose correta para dessecação, além da escolha da formulação mais adequada para cada ambiente, visto que a formulação de sal de K+ acelerou a cinética de mortalidade para o capim Urochloa.

New herbicides for soybean cultivation, mainly mixtures, have been launched on the market. However, little is known about the actual effects of these mixtures on the crop, and studies are needed to verify the sensitivity of cultivars to these herbicides. This work aimed to evaluate the sensitivity of soybean cultivars to the commercial mixture of pre-emergent herbicides sulfentrazone + diuron. The experiment was conducted in a greenhouse in a completely randomized design, with four replications, in a 20 x 3 factorial. Factor A was composed of 20 soybean cultivars. Factor B comprised two doses of sulfentrazone + diuron, being 175 + 350 g ha-1, and 350 + 700 g ha-1, equivalent to 1 and 2 L commercial product (cp) ha-1, in addition to a control treatment (zero dose). The variables evaluated were phytotoxicity, FSII activity, relative electron transport rate (rETR), shoot length, and shoot dry mass (SDM). The data were subjected to analysis of variance, and the means were grouped using the Skott-Knott test (p < 0.05). The mixture of sulfentrazone + diuron caused negative changes in the physiological and growth characteristics, especially at the highest dose evaluated. However, variability was observed in the sensitivity of the studied cultivars. HO Amambay, HO Iguaçu, HO Paraguaçu, HO Pirapó, Lança IPRO, Lótus IPRO, M6410 IPRO, TMG 2356 IPRO, TMG 2359 IPRO, and TMG 2364 IPRO cultivars were more sensitive. Therefore, it is concluded that the selectivity of the sulfentrazone + diuron mixture depends on the dose applied and the soybean cultivar.

Dois experimentos foram conduzidos para avaliar a importância de aplicação sequencial para o fluroxipir-metílico no controle de buva, bem como definir o melhor intervalo e produto de contato a ser usado em sequencial. O primeiro experimento avaliou o controle de Conyza spp. em aplicação única de fluroxipir-metílico (240 g e.a. ha-1 fluroxipir) + glifosato (1.200 g e.a. ha-1), glufosinato de amônio (400 g i.a. ha-1), glufosinato de amônio + saflufenacil (400 g i.a. ha-1+ 35 g i.a. ha-1), e diquate (400 g i.a. ha-1). O segundo experimento avaliou intervalos e herbicidas em aplicação sequencial, conduzido em esquema fatorial 4X3 + 1, em que os tratamentos fatoriais tiveram uma aplicação de fluroxipir-metílico + glifosato, com primeiro fator referente aos intervalos de três, seis, 10 e 15 dias entre as aplicações, e segundo fator referente à aplicação de glufosinato de amônio, glufosinato de amônio + saflufenacil, e diquate. Os herbicidas foram usados em mesma dose do experimento anterior, e o tratamento adicional corresponde à uma testemunha não aplicada. O controle foi analisado aos 14 e 28 dias após aplicação sequencial (DAA), as médias foram comparadas por Tukey e Dunett (P ≥ 0,05), e os intervalos analisados em regressão. A aplicação única de herbicidas não foi efetiva no controle de buva, em que aos 14 DAA houve relação positiva entre o aumento do período de intervalo e níveis de controle, com controle máximo atingido aos 15 dias. Dentre os produtos utilizados em aplicação sequencial, houve destaque para a mistura de glufosinato + saflufenacil.

Barnyardgrass (Echinochloa crus-galli) is one of the most troublesome weeds in irrigated rice cultivation and has increasingly impacted rainfed crops due to the emergence of herbicide-resistant populations. Understanding its germination dynamics is crucial for developing and implementing effective management strategies. Additionally, since barnyardgrass research relies on growing plants from seeds, its dormancy characteristics are of particular interest. The present study aimed to evaluate the influence of postharvest age on barnyardgrass seed germination and the effectiveness of different dormancy-breaking methods in susceptible and herbicide-resistant populations. Germination rate (G), germination speed index (GSI), and seed viability, assessed using the topographic tetrazolium test, were measured in seed lots with four different postharvest ages: two years, one year, two months, and one day postharvest. The seeds were subjected to 15 dormancy-breaking methods, including temperature variation and the use of solutions containing H2SO4, KNO3, and GA3. Seeds that were one or two years old showed germination rates exceeding 90%, regardless of the method used. In contrast, seeds aged two months or one day postharvest only germinated when exposed to 40°C for seven days, with G values of 25.2% and 5.9%, respectively. Both herbicide-susceptible and resistant barnyardgrass populations exhibited similar dormancy levels and responses to dormancy-breaking methods. The results indicate that newly harvested seeds have high dormancy levels, and specific methods are only partially effective in overcoming barnyardgrass seed dormancy.

The use of herbicides applied at pre-emergence is an important measure for managing Amaranthus hybridus. However, the presence of straw and rainfall regime after application may alter the efficacy of these herbicides. This study was carried out with the objective of evaluating the effect of different straw mass on the soil surface and different rainfall regimes on the efficacy of imazethapyr + flumioxazin in controlling Amaranthus hybridus. Three greenhouse experiments were conducted and replicated for two years. Experiment 1 consisted of five Brachiaria humidicola straw mass (0, 2, 4, 6 and 8 Mg ha-1) with 20 mm rainfall simulation after herbicide application; in experiment 2, six times to the first rainfall (0, 3, 6, 9, 12 and 15 days) after herbicide application were assessed; and experiment 3 involved four rainfall volumes (0, 10, 30 and 50 mm) after herbicide application. The presence of straw did not alter the efficacy of imazethapyr + flumioxazin, even at the highest mass assessed (8 Mg ha-1) and rainfall of 20 mm. In the absence of herbicide, the highest B. humidicola weight reduced emergence of A. hybridus by 63% when compared to the straw-free treatment. The herbicide imazethapyr + flumioxazin demonstrated flexibility in response to rainfall regime, with total control of A. hybridus even after15 days of drought and up to 50 mm of rain after spraying. The herbicide imazethapyr + flumioxazin was effective against A. hybridus in all straw and rainfall situations evaluated.

This study aimed to evaluate the effects of application time and addition of diuron to clethodim and diquat on the control of sourgrass. Two experiments were conducted with sourgrass plants, applying spray solutions comprising the herbicide clethodim (216 g a.i. ha-1), clethodim + diquat (216 + 400 g a.i. ha-1), and clethodim + diquat + diuron (216 + 400 + 400 g a.i. ha-1) three times (08:00, 12:00, and 16:00) in addition to the control. Control and mass evaluations of sourgrass plants were performed in both experiments, and the relative rate of linear electron transport by PSII and leaf accumulation of hydrogen peroxide were evaluated in the greenhouse experiment. The results indicated an increase in sourgrass control with the addition of diuron to the mixture, resulting in 100% control in the application performed at 16:00. Spray solutions containing photosystem inhibitors should be applied at 08:00 and 16:00 to improve plant control. These mixtures applied under lower light intensity showed greater inhibition of the relative electron transfer rate and increased H2O2 concentrations with greater accumulation of this reactive oxygen species (ROS; 17894.17 nmol g-1 FW) after the application of clethodim + diquat + diuron at 16:00. The addition of diuron was necessary for total plant control, resulting in greater inhibition of photosynthetic activity and accumulation of ROS. Objetivou-se avaliar o efeito do horário de aplicação e da adição de diuron ao clethodim e diquat sobre o controle de capim-amargoso. Foram realizados dois experimentos com plantas de capim-amargoso, aplicando-se as caldas de pulverização compostas pelo herbicida clethodim (216 g i.a. ha-1), clethodim + diquat (216 + 400 g i.a. ha-1) e clethodim + diquat + diuron (216 + 400 + 400 g i.a. ha-1) em três horários (8; 12 e 16 h), além da testemunha.

Digitaria insularis (sourgrass) is a monocotyledon weed of difficult control and high invasive behavior. Atrazine is widely applied in the Americas to control weeds in maize culture, but its efficiency against D. insularis is limited. The incorporation of atrazine into poly(epsilon-caprolactone) nanocapsules increased the herbicidal activity against susceptible weeds; however, the potential of this nanoformulation to control atrazine-tolerant weeds including D. insularis has not yet been tested. Here, we evaluated the post-emergent herbicidal activity of nanoatrazine against D. insularis plants during initial developmental stages. The study was carried out in a greenhouse, using pots filled with clay soil. Plants with two or four expanded leaves were treated with conventional or nanoencapsulated atrazine at 50 or 100% of the recommended dosage (1,000 or 2,000 g • ha-1), followed by the evaluation of physiological, growth, and control parameters of the plants. Compared with conventional herbicide, both dosages of nanoatrazine induced greater and faster inhibition of D. insularis photosystem II activity at both developmental stages. Atrazine nanoencapsulation also improved the control of D. insularis plants, especially in the stage with two expanded leaves. In addition, nanoatrazine led to higher decreases of dry weight of fourleaved plants than atrazine. The use of the half-dosage of nanoatrazine was equally or more efficient in affecting most of the evaluated parameters than the conventional formulation at full dosage. Overall, these results suggest that the nanoencapsulation of atrazine potentiated its post-emergent herbicidal activity against D. insularis plants at initial developmental stages, favoring the control of this atrazine-tolerant weed.

Environmental factors and the addition of adjuvants to the spray tank mix may interfere with glyphosate efficiency in hairy fleabane control. The objective of this study was to evaluate the effect of air temperature and the addition of ammonium sulfate (NH 4) 2 SO 4 to glyphosate in the control of glyphosate-resistant (GR) and-susceptible (GS) hairy fleabane. Treatments consisted of air temperatures of 12°C and 25°C, six doses of glyphosate from zero to 2,880 g • ha-1 , the presence or absence of (NH 4) 2 SO 4 in the spray solution, and one GS and another GR biotype. At the lowest tested dose (180 g • ha-1), control of the GR biotype was 91% and 20% when the plants were kept at 12°C and 25°C, respectively, reducing the resistance factor (RF) by 9.30 times and was associated to the reduction of temperature. The addition of (NH 4) 2 SO 4 increased the control by 10-20% at high glyphosate doses and at 25°C. The resistance of hairy fleabane to glyphosate was completely reversed when the plants were maintained at 12°C. At this temperature, resistant plants were controlled even at doses well below that recommended for the control of this species. At 25°C, a dose four times higher than that recommended was required for satisfactory control. At the field level, under situations of low temperatures, it was possible to improve the efficacy of glyphosate applications in hairy fleabane control, if there were no other mechanisms of resistance involved.