Christiane Augusta Diniz Melo

Danos visuais e anatômicos causados pelo glyphosate em folhas de Eucalyptus grandis

Symptomatology is one of the most important criteria used to determine the damages caused by biotic and abiotic factors in plants. However, microscopic aspects are needed to elucidate intoxication mechanisms and early injury diagnosis. This work aimed to evaluate the effects of four commercial glyphosate formulations under simulated spray drift (Scout®, Roundup NA®, Roundup transorb® and Zapp QI®) on the morphoanatomy of six Eucalyptus grandis clones (UFV01, UFV02, UFV03, UFV04, UFV05 and UFV06). Following glyphosate application (129.6 g ha-1), symptoms were monitored daily and, at 14 days, leaf samples from the regions without visible symptoms were collected for microscopic analysis. All clones presented chlorosis and necrosis at the fourth day of glyphosate exposure, regardless of the formulation used. The UFV04 clone did not show any anatomical damage. The other clones suffered plasmolysis, cellular collapse, hypertrophy and formation of cicatrisation tissue. However, changes in leaf blade thickness were not observed. Plants exposed to Roundup transorb® presented the greatest visible intoxication percentage. Anatomically, plants exposed to Roundup NA® showed a higher number of damages. Analysis considering both anatomic and visible damages showed that UFV06 clone was the most susceptible to the formulations tested. The results confirmed the diagnostic and prognostic value of visual and anatomical analysis, respectively, and showed that these parameters are essential to evaluate clone susceptibility and the the phytotoxic potential of herbicides.

Residual effect of sulfentrazone, isoxaflutole and oxyfluorfen in three soils

The physical and chemical properties of soils, as well as climatic conditions, influence the behavior of herbicides applied in pre-emergence. This work aimed to evaluate the residual effect of sulfentrazone, isoxaflutole and oxyfluorfen in three soils. The trial was conducted in a protected environment in a randomized block experimental design, with four replications. The treatments for each soil were arranged in a 3 x 5 factorial, being three herbicides and five sowing periods after herbicide application. Sulfentrazone, isoxaflutole and oxyfluorfen were applied at 0.5 kg ha-1, 0.72 kg ha-1 and 0.113 kg ha-1, respectively, on plastic pots with 250 mL volume, previously filled with the two clay texture soils and the sandy loam texture soil. Subsequently, the bioindicator species Sorghum bicolor was sown at 0, 15, 30, 45 and 60 days after application (DAA). A control with no herbicide treatment was sown at different times for each soil and used as a comparison in the evaluations. At 21 days after sowing in each season, intoxication and plant growth were evaluated by means of shoot dry mass. Sorghum plants in the clay soil with 9.0 dag kg-1 of organic matter (O.M.), submitted to the application of isoxaflutole, sulfentrazone and oxyfluorfen, produced shoot dry mass over the control to 34, 20 and 40%, respectively, at 60 DAA. In the sandy loam soil, it was observed a high residual effect of sulfentrazone and oxyfluorfen, and a decrease in the residual effect of isoxaflutole over time, with 80, 90 and 40% control at 60 DAA, respectively. In the clay soil with 4.4 dag kg-1 of O.M., the herbicide isoxaflutole was found to lose control efficacy over time, unlike oxyfluorfen, which showed practically constant control in all the evaluated periods, and sulfentrazone, which showed high residual effect during the study period. The inherent characteristics of each herbicide, as well as the differences in organic matter content and texture between the soils influence the persistence of sulfentrazone, isoxaflutole and oxyfluorfen in the soil. Greater residual effect of oxyfluorfen was observed in sandy loam soil, and isoxaflutole in clay soil with high content of organic matter, while sulfentrazone presented high residual effect in the three soils.The physical and chemical properties of soils, as well as climatic conditions, influence the behavior of herbicides applied in pre-emergence. This work aimed to evaluate the residual effect of sulfentrazone, isoxaflutole and oxyfluorfen in three soils. The trial was conducted in a protected environment in a randomized block experimental design, with four replications. The treatments for each soil were arranged in a 3 x 5 factorial, being three herbicides and five sowing periods after herbicide application. Sulfentrazone, isoxaflutole and oxyfluorfen were applied at 0.5 kg ha-1, 0.72 kg ha-1 and 0.113 kg ha-1, respectively, on plastic pots with 250 mL volume, previously filled with the two clay texture soils and the sandy loam texture soil. Subsequently, the bioindicator species Sorghum bicolor was sown at 0, 15, 30, 45 and 60 days after application (DAA). A control with no herbicide treatment was sown at different times for each soil and used as a comparison in the evaluations. At 21 days after sowing in each season, intoxication and plant growth were evaluated by means of shoot dry mass. Sorghum plants in the clay soil with 9.0 dag kg-1 of organic matter (O.M.), submitted to the application of isoxaflutole, sulfentrazone and oxyfluorfen, produced shoot dry mass over the control to 34, 20 and 40%, respectively, at 60 DAA. In the sandy loam soil, it was observed a high residual effect of sulfentrazone and oxyfluorfen, and a decrease in the residual effect of isoxaflutole over time, with 80, 90 and 40% control at 60 DAA, respectively. In the clay soil with 4.4 dag kg-1 of O.M., the herbicide isoxaflutole was found to lose control efficacy over time, unlike oxyfluorfen, which showed practically constant control in all the evaluated periods, and sulfentrazone, which showed high residual effect during the study period. The inherent characteristics of each herbicide, as well as the differences in organic matter content and texture between the soils influence the persistence of sulfentrazone, isoxaflutole and oxyfluorfen in the soil. Greater residual effect of oxyfluorfen was observed in sandy loam soil, and isoxaflutole in clay soil with high content of organic matter, while sulfentrazone presented high residual effect in the three soils.

Soil microorganisms and their role in the interactions between weeds and crops

A competicao entre plantas daninhas e culturas e um topico de grande interesse, uma vez que essa interacao pode causar grandes perdas na agricultura. Apesar de alguns estudos nesse tema, pouco se sabe sobre a importância dos microrganismos do solo na modulacao dessa interacao. As plantas competem por agua e nutrientes presentes no solo e a capacidade das especies em absorver esses recursos pode ser diretamente afetada pela presenca de alguns grupos microbianos comumente encontrados no solo. Os fungos micorrizicos arbusculares (FMA) sao capazes de se associar com as raizes das plantas, o que afeta a capacidade das diferentes especies em absorver agua e nutrientes do solo, promovendo alteracoes no crescimento. Outros grupos podem promover alteracoes positivas ou negativas no crescimento das especies vegetais, a depender da identidade das especies microbianas e vegetais envolvidas nas diferentes interacoes, alterando a capacidade competitiva de cada uma delas. Estudos recentes tem demonstrado que as plantas daninhas sao capazes de se associar com fungos micorrizicos arbusculares nos ambientes agricolas, e que a colonizacao das raizes por esses fungos e afetada pela presenca de outras plantas daninhas ou de culturas. Alem disso, as plantas daninhas tendem a apresentar interacoes positivas com a microbiota do solo, ao passo que as culturas apresentam interacoes neutras ou negativas. A competicao entre plantas daninhas e culturas promove alteracoes na comunidade microbiana do solo, que se torna diferente daquelas observadas nas monoculturas, afetando a capacidade competitiva das especies vegetais. Quando colocadas em competicao, plantas daninhas e culturas apresentam diferentes comportamentos relacionados a microbiota do solo, sendo que as plantas daninhas apresentam maior dependencia de associacoes com microorganismos do solo, em relacao as culturas, para aumentar seu crescimento. Esses dados demonstram a importância dos microorganismos do solo na modulacao das interacoes entre plantas daninhas e culturas nos ambientes agricolas. Novas perspectivas e hipoteses sao apresentadas para guiar as futuras pesquisas nessa area.

Crescimento de mudas de clones de eucalipto submetidos à deriva simulada de diferentes herbicidas

Among the possibilities of weed management, the chemical method is the most used one. However, a potential problem presented by this method is the accidental drift. Thus, knowledge on the risk and on how to quantify it and its effect on the crop is essential for a correct use of these products in weed management. The objective of this work was to study the effect of simulated herbicide drift through underdosing in the growth of two eucalyptus clones seedlings, considering the possible extension of their use. The herbicides used were atrazine, nicosulfuron and tembotrione, and formulated mixtures were foramsulfurom + iodosulfurom-methyl and fluazifop-p-butyl + fomesafen, applied at doses corresponding to 3, 6 and 12% of the recommended dose. It was evaluated percentage of intoxication, height, stem diameter and shoot dry mass. Herbicides affected the growth of eucalyptus plants, mainly by limiting increase in shoot dry mass. The risk of productivity loss in case of intoxication if drift occurs is reduced with the use of atrazine, foramsulfurom + iodosulfurom-methyl and tembotrione and it was higher with the use of fluazifop-p-butyl + fomesafen and nicosulfuron. Among the tested products, tembotrione is the one that shows the greatest potential to be used in eucalyptus areas.

Competition of weeds with coffee plants, in two times of infestation.

The aimed of this work was to evaluate the weed interference installed at 60 and 180 days after coffee seedlings transplanted in pots contend 25 dm3 of substrate. The experiment was arranged in a randomized blocs, with four replications, in factorial design (2 x 4 x 2), with two weed species (Brachiaria decumbens and Brachiaria plantaginea), cultured per 90 days, in four densities (zero, two, four and six plants per pot), together with coffee seedlings of different ages: 60 and 180 days after transplanted. In the moment of the experiment harvest was evaluated the increment in plant height, in leaf area and in girth diameter of the coffee, dry matter of weeds and coffee, and coffee root density. It also estimated the leaf mass ratio, stem mass ratio, root mass ratio, root system/shoot ratio of coffee plants. The weeds provided negative interference in the characteristics evaluated. Verified was smaller increase of height, leaf area and total dry matter of coffee plants with the increase of weed density. The effects of plants interference were bigger when the interference was installed sooner. In this case smaller occurred accumulation of growth variables; however both grasses behaved of similar way not differing for the most variables. When the competition was installed later the coffee plants were more sensible to competition the B. plantaginea in relation to B. decumbens. The increase of weed densities promoted bigger allocation of photoassimilates for the shoot part in detriment to coffee root system.

The Allelopathic Effect of Eucalyptus Leaf Extract on Grass Forage Seed

This study aimed to evaluate the allelopathic effect of various concentrations of an aqueous extract of eucalyptus leaves on Urochloa decumbens and Panicum maximum seeds. The extract was prepared from Eucalyptus urograndis leaves that were milled and mixed with distilled water in a 1:9 milled leaves: water ratio to obtain an extract with a defined concentration of 100%. In addition, dilutions of 50%, 25% and 12.5% were prepared, and a 0% dilution was used as a control. The experiment followed a completely randomized design, with four replicates, each of 50 seeds of U. decumbens and 50 seeds of P. maximum, arranged on filter paper moistened with each concentration of extract in a Gerbox plastic box. The results demonstrated the allelopathic potential of E. urograndis aqueous extracts applied to the seeds of U. decumbens and P. maximum. The 50% and 100% concentrations of leaf extract most strongly inhibited the germination, vigor and seedling growth of U. decumbens and P. maximum. The germination speed index and the root length were the characteristics that were most affected by the potentially allelopathic substances contained in the eucalyptus extracts at all concentrations.

CRESCIMENTO INICIAL E CONCENTRAÇÃO DE NUTRIENTES EM CLONES DE Eucalyptus urophylla x Eucalyptus grandis SOB INTERFERÊNCIA DE PLANTAS DANINHAS

The presence of weeds in eucalypt plantations, especially in the first two years, can result in losses of productivity because it reduces the efficiency of growth resource use by the crop. The objective of this study was to evaluate the effects of weed interference in two Eucalyptus urophylla x Eucalyptus grandis clones on initial growth and nutrient foliar concentration in the crop and weeds. The experiment was conducted in a factorial 2 x 5 +7 in which it used two clones of Eucalyptus urophylla x Eucalyptus grandis, identified as CNB001 and CNB016, competing with five weeds Urochloa decumbens, Ipomoea nil, Commelina diffusa, Spermacoce latifolia and Panicum maximum. Also the two eucalypt clones and the five weeds were grown in monoculture as a standard for comparison. It was used a completely randomized design with four replications. The eucalypt initial growth was evaluated by plant height, stem diameter, branches number, leaf area, dry matter and nutrient content in the leaves of eucalyptus. Nutrient concentration in leaves weed also was evaluated. The CNB001 clone showed initial growth upper at the clone CNB016. Free of weed interference both clones presented similar foliar contents for most nutrients. Clone CNB016 was more sensitive to competition with weeds than clone CNB001, being its initial growth most harmed by Ipomoea nil and concentration of nutrients reduced by Panicum maximum, Urochloa decumbens and Commelina diffusa. Panicum maximum showed greater interference with clone CNB001 while Ipomoea nil showed low negative influence in growth and nutrient concentration of crop. The weeds have high ability to extract nutrients from the soil in competition with Eucalyptus urophylla x Eucalyptus grandis clones. The interference imposed on the culture is dependent on weed species and eucalypt genotype.

Impacto de sulfentrazona, isoxaflutol e oxyfluorfem sobre a microbiota de dois solos florestais

Questions regarding the application of pre-emergence herbicides for control weeds in eucalyptus are noteworthy due to the impact of this practice on the environment, particularly on soil microbial activity and beneficial micro-organisms such as mycorrhizal fungi and phosphate solubilizers. The aim of this research was to study the impact of applying herbicides sulfentrazone isoxaflutole and oxyfluorfen on mycorrhizal colonization, microbial biomass and microbial activity of two forest soils cultivated with eucalyptus. The trial was conducted in a greenhouse using two soils, one clay and sandy loam distributed in 12 dm3 pots. The 4x3 factorial design was used , with three herbicides (sulfentrazone, oxyfluorfen, isoxaflutole) over the untreated control and three assessments (5, 20 and 70 days after application (DAA)), in a completely randomized design with four replications . After herbicide application seedlings of the hybrid Eucalyptus grandis x Eucalyptus urophylla. We evaluated the microbial biomass of the soil respiration rate, the quotient and the metabolic potential of solubilization of inorganic phosphate at 5, 20 and 70 DAA. At 70 DAA verified the percentage of roots colonized by mycorrhizal fungi and spore viability in the soil. The sulfentrazone, isoxaflutole and oxyfluorfen as well as the time of application affected the microbiological indicators differently. In the sandy loam soil sulfentrazone was more harmful to microbial biomass, mycorrhizal colonization and microorganisms solubilizing inorganic phosphate. In clay soil, however, the application of the three herbicides did not affect microbial biomass, but reduced root colonization of eucalyptus by mycorrhizal fungi and the potential solubilization of inorganic phosphate. The sulfentrazone stood for caused an increase in the number of non-viable spores of mycorrhizal fungi in the soil.

Efeito do herbicida tembotrione sobre o desenvolvimento da batata

Os residuos do herbicida tembotrione no solo, proveniente de cultivos de milho, podem afetar o crescimento de culturas sensiveis, como a batata, em sucessao. Neste sentido, objetivou-se avaliar o efeito do herbicida tembotrione sobre o crescimento e o desenvolvimento da batateira. Realizou-se um experimento de campo em delineamento em blocos casualizados, com quatro repeticoes. Os tratamentos foram incorporados ao solo um dia antes do plantio da batata cultivar Atlantic e constituidos de quatro doses de tembotrione: 8,4; 16,8; 33,6 e 50,4 g ha -1 , representando 8,4; 16,8; 33,6 e 50% da dose recomendada para a cultura do milho, e um tratamento controle (sem herbicida e capinada). Aos 60 e 90 dias apos o plantio foram avaliadas a massa de materia fresca de tuberculo (MMFT), o numero de hastes (NH), o numero de tuberculos (NT) por planta e a massa de materia seca total (parte aerea + haste) (MMST). A MMFT, NT e MMST decresceram com o aumento das doses do tembotrione, sendo que as maiores reducoes encontradas, nas duas epocas avaliadas, foram na dose de 50,4 g ha -1 i.a. O numero de hastes nao foi influenciado pelas doses do herbicida tembotrione independente da epoca avaliada. Os resultados obtidos indicaram que a presenca de tembotrione no solo reduziu o crescimento e a quantidade de tuberculos produzidos pela batateira.

Seletividade inicial de herbicidas aplicados em pós-emergência da crotalária

Among the practices that aim to confer sustainability of the agricultural soil, the use of green manure and/or cover crops such as crotalaria are advocated. The management of weeds is one of the practices for the success of crotalaria. However, the information about the selectivity of herbicide are scarce and these are of paramount importance. The objective of this study was to evaluate the selectivity of different herbicides applied in post-emergence of showy crotalaria ( Crotalaria spectabilis ). Two experiments were conducted in a greenhouse in a randomized completely randomized design with four replications. In the first one the following herbicides were tested. The first experiment involved the following herbicides (g. i.a.ha -1 ): atrazine (500 and 1000), bentazon (720), carfentrazone-ethyl (3.75), clomazone (400), diclosulam (20), diuron (800), ethoxysulfuron (18), flumioxazin (10), mesotrione (60), oxadiazon (500), tembotrione (40), atrazine + flumioxazin + carfentrazone-ethyl (300 + 5 + 2), and a control without application. In the second were used, bentazon (400), clomazone (400), diclosulam (10 and 15), diuron (400), ethoxysulfuron (15), bentazon + diclosulam (200 + 7.5), diclosulam + diuron (7.5 + 200), bentazon + diuron (200 + 200) and a control without application. Phytotoxicity was evaluated at 7, 14, 21 and 28 days after application (DAA) and aerial dry matter (ADM) at 28 DAA. In both experiments the herbicides bentazon, clomazone, diclosulam and ethoxysulfuron caused low injuries to the crop and low reduction in ADM. The herbicides atrazine, mesotrione, oxadiazon and atrazine + flumioxazin + carfentrazone-ethyl provided high levels of injuries and high reduction in ADM. The herbicides bentazon, clomazone, diclosulam and ethoxysulfuron were selectivity for post-emergence application of the crop.