The aim was to evaluate the selectivityand weed control ofherbicides atrazine, nicosulfuron, mesotrione and tembotrione, applied alone and associated, in post-emergence ofmaize. Were carried out two experiments, one in the field in a randomized complete block design with four replications and eleven treatments, the second in greenhouse in a completely randomized design, with four replications and ten treatments. The treatments were composed of isolated and associated herbicides. Treatments were applied V4 stage of plants. For first experiment, crop injury and control evaluations were performed, as well as variables related to agronomic performance (plant height, ear insertion height, prolificacy index, yield and mass of 1,000 grains) and mass of weeds. For second experiment, evaluations of crop injury, height, diameter and dry mass of plants were performed. The lower yield for experiment one was verified in the treatment where only mesotrione was applied, which was attributed to the lower control of monocotyledons weeds. Crop injury were observed at 21 DAA in both experiments, but not exceeding 7.5%. All treatments were considered selective tomaize. The herbicides atrazine, nicosulfuron, mesotrione and tembotrione, at associations, were effective in the weed control, except the association atrazine + mesotrione.
Thus, the application of herbicide combinations may be an excellent integrated management strategy. The association ofglyphosate with other herbicides is effective in weed management. However, associations can affect the full development and even yield ofmaize RR, because due to the different compositions of the products, there may be synergistic relationships that result in crop injury to the crop. The purpose of this work was to evaluate the tolerance ofmaize hybrids 2B810 PW and 30F35 HR subjected to the application ofherbicides alone and in combination.
According to several authors, the uptake amount of foliar-applied herbicides usually varies with the morphological and anatomical traits of leaves, since an increase in the thickness of the cuticle layer may slower herbicide uptake (Wanamarta e Penner, 1989; Chachalis et al., 2001; Ferreira et al., 2002; Hoss et al., 2003; Huangfu et al., 2009), that is, the leaf surface and leaf anatomy may affect the efficacyofglyphosate uptake in weeds . Sher- rick et al. (1986) investigated the effects of adju- vants and the environment during plant develo- pment on the level ofglyphosate absorption and translocation in Convolvulus arvensis L. and con- firmed that the thickness of the cuticle of weed affects the herbicide’s level ofefficacy. Our study clearly illustrates morphological disparities in the epidermal and anatomical features of young and mature leaves of A. donax, but the differences did not explain their susceptibility difference toglyphosate.
The treatments did not influence the HEI, NRE and PMG (Table 7). Studies show that phytotoxic effects may influence crop yield components (FELISBERTO et al., 2017; BASSO et al., 2018; GALON et al., 2018b). However, this behavior may be related to several factors, such as cultivar or hybrid characteristics, formulation, dose and time of herbicide application, crop management, and climatic conditions (VALDERRAMA et al., 2011). The number of grains per row (NFG) and yield (PROD) showed differences only for the infested control. When comparing the mean of herbicide treatments and the infested control, an increase of approximately 43% was observed. The grain yield ofmaize increased by 14%, when comparing the averages of tank mixtures of the products, applied in pre- and postemergence, with glyphosate in isolated use. Thus, it is clear that the associations ofherbicidestoglyphosate applied in pre- or postemergence improve its efficacy in controlling weeds in maize, which reflects in higher grain yield and also facilitates the management ofglyphosate resistant or tolerant weeds. BASSO et al. (2018) reported results similar to these when they found higher maize Table 5. Control (%) of turnip – R. sativus L. weed of Forseed 2A521 PW maize hybrid as a function of herbicide applications
The increase in height of citrus plants 15 DAA was considered low or zero regardless of the chemical treatment analyzed, as well as the control without application ofherbicides (Table 5). These results also indicated that the seedlings were still adapting to the new conditions in the pots. The following evaluations, at 30, 60 and 90 DAA, showed that the directed spraying of saflufenacil, applied singly and in combination with glyphosate, did not had any negative effects on plant growth at the rates studied (Table 5).
impair the biological control, if the products are not selective to Telenomus podisi and Trissolcus basalis, which are important stink bug egg parasitoids. This study aimed to assess the selectivityof 15 pesticides registered for soybean crop on adults of T. podisi and T. basalis. Three laboratory bioassays were performed, totaling 18 treatments, in a completely randomized design, with four replications. The insecticides (g or mL of a.i.) imidacloprid + beta-cyfluthrin (0.25 + 0.03), deltamethrin (0.06), thiamethoxam + lambda-cyhalothrin (0.27 + 0.35), acephate (1.87) and fenitrothion (1.25) are harmful to both parasitoids species. Flubendiamide (1.20), diflubenzuron (2.00), Bacillus thuringiensis (0.08) and lufenuron (0.12) are innocuous to both parasitoids. The fungicides azoxystrobin + flutriafol (0.31 + 0.31), trifloxystrobin + prothioconazole (0.37 + 0.44), pyraclostrobin + metconazole (0.33 + 0.12) and trifloxystrobin + cyproconazole (0.94 + 0.40) are innocuous to T. podisi, but slightly harmful to T. basalis. The herbicides glufosinate ammonium salt (0.50) andglyphosate isopropylamine salt (1.20) are innocuous to both parasitoids.
The expansion of agricultural areas in south central Brazil with glyphosate-resistant (GR) crops (also referred to as Roundup Ready (RR) crops), mainly soybean and corn, has contributed to the strong selection of resistant weed biotypes. High selection pressure exerted by glyphosate, use during post- emergence in GR crops, promotes the growth of resistant weeds (Yanniccari, Vila-Aiub, Istilart, Acciaresi, & Castro, 2016). Herbicide resistance occurs when the weeds survive, complete their life cycles and reproduce by seed after herbicide application, at doses normally lethal to wild weed biotypes (Vencil et al., 2012). Biologically, herbicide-resistant populations of weeds are naturally present but occur at low densities (Alcántara-de la Cruz et al., 2016). The emergence of resistant biotypes is due to different mechanisms of resistance, which may be related to the target site of the herbicide (Powles & Yu, 2010; Heap & Duke, 2017). The most important factors influencing the selection of herbicide-resistant biotypes are the intensity of its use, the efficacyof resistance mechanisms, herbicide specificity with respect to mechanism of action, weed emergency patterns and efficiency ofalternative control methods (Rubim, 1991).
The glyphosate [N-(phosphonomethyl) glycine] is a non-selective systemic herbicide used during the past 35 years. It is the most important herbicide worldwide due to its versatility of using in agricultural and forest areas. The glyphosate is one of the main herbicides used for weed control in eucalypt plantations (COSTA et al., 2012a) due to a few products are officially registered and due in addition to some favorable characteristics of the glyphosate (TUFFI SANTOS et al., 2007), such as the high efficacyand the large spectrum of control, the low toxicity to mammals, birds, and fishes, the fast degradation by microorganisms, and the very short soil persistence (PRESTON; WAKELIN, 2008). Showing a large spectrum and being a non-selective herbicide, the glyphosate drift may cause deleterious effects on the growth, development, and production, or even kill plants of the crops of interest (CARVALHO et al., 2012a). However, a different behavior may be observed among distinct plants of the same species when they are exposed to the glyphosate drift. Thus, the objective of this research was to evaluate the growth pattern of four clones of Eucalyptus grandis x Eucaliptus urophylla (Eucalyptus urograndis), known as C219 (commonly cultivated), GG100, I144, and I224 (of recent
Owing to the crops seasonality and subsequent periodic/seasonal application ofherbicides, their input to the aquatic systems is typically intermittent. Consequently, fish exposure to this type of contaminants can be short and followed by a period of permanence in non-contaminated areas. Bearing this in mind, the assessment of genotoxic endpoints in fish after removal of the contamination source appears as a crucial step to improve the knowledge on the dynamics of herbicide induced genotoxicity, as well as to determine the actual magnitude of risk posed by these agrochemicals to fish. Therefore, the present study intended to shed light on fish ability to recover from the DNA damage induced by short-term exposures to the herbicide formulations Roundup ® (glyphosate-based) and Garlon ® ( triclopyr-based) upon the exposure cessation. European eel (Anguilla anguilla) was exposed to the previous commercial formulations, for 3 days, and allowed to recover for 1, 7 and 14 days (post-exposure period). The comet assay was used to identify the DNA damage in blood cells during both exposure and post-exposure periods. As an attempt to clarify the DNA damaging mechanisms involved, an extra-step including the incubation of the nucleotides with DNA lesion-specific repair enzyme was added to the standard comet. The genotoxic potential of both herbicides was confirmed, concerning the exposure period. In addition, the involvement of oxidative DNA damage on the action of Roundup ® (pointed out as pyrimidine bases oxidation) was demonstrated, while for Garlon ® this damaging mechanism was less evident. Fish exposed to Garlon ® , though presenting some evidences towards a recovery tendency, didn’t achieve a complete restoration of DNA integrity. In what concerns to Roundup ® , a recovery was evident when considering non-specific DNA damage, on day 14 post-exposure. In addition, this herbicide was able to induce a late oxidative DNA damage (day 14). It was also recognized that blood cells of A. anguilla exposed to Roundup ® were more successful in repairing damage with a non-specific cause, than that associated to bases oxidation. Overall, the present findings highlighted the genetic hazard to fish associated to the addressed agrochemicals, reinforcing the hypothesis of long-lasting damage.
Martins et al. (2012) observed that tank mixtures with Carfentrazone + Glyphosate or 2,4- D + Glyphosateand 2,4-D isolated application presented the best control percentagens of Commelina benghalensis. The same authors also evidenced the synergism in the mixture between Carfentrazone + Glyphosato when observed that these products applied alone did not provide satisfactory effects in the control of C. benghalensis.
Plants grown in soils at 280 DAA, evaluated at 20 DAS, a mild intoxication and lower chlorophyll content was observed for the 2,4-D + picloram residual, however, without affecting the plants height; while the other treatments did not affect the analyzed variables. In the evaluations at 40 DAS, a moderate intoxication, lower chlorophyll content, lower plant height, and lower shoot dry mass was observed for the 2,4-D + picloram residual compared to the others treatments, without affecting the roots dry mass. At the same evaluation date, the others treatments did not affect the analyzed variables. Among all the legumes evaluated, the lablab bean was the only one that, despite the injuries observed, were able to develop in soil with 2,4-D + picloram residual. Possibly, this occurs due to the tolerance mechanism of this species to picloram. According to Carmo et al. (2008) and Madalão et al. (2012), the plants that grow on soils
These values were higher than those analyzed in the greenhouse. One hypothesis to explain these different results may be in the different plants stages at the time of collection of plant material for the analyses, a fact also confirmed by Fukushima et al. (2000). This demonstrates that apparently a temporary effect on the change of plant lignin contents occurs, but these changes do not persist until the final stages of the cycle, which does not contribute to significant changes in the composition ofmaize stover.
results obtained in this paper appear to be related to the degree of competition experienced by the components, mainly for water and light. Maize intercropped had higher values of leaf water potential, stomatal conductance, transpiration and photosynthesis than as sole crop. Intercropped cowpea had higher values of leaf water potential but lower stomatal conductance, transpiration and photosynthesis than sole cowpea. Maize productivity increased 18% in relation to sole crop whereas a 5% decrease was observed with cowpea. Despite these facts the Land Equivalent Ratio obtained was 1.13 indicating intercropping advantage over the sole system. The higher partial Land Equivalent Ratio observed for maize suggests that this specie was the main component influencing the final productivity of the intercropping system studied.
Abstract – Evaluation was carried out for the interrelation between maizeand Urochloa brizantha cv. Marandu and Urochloa ruziziensis, with and without application ofglyphosate underdoses, and the effects of this management on weeds. For each forage species, an experiment was conducted in randomized block design, with subdivided plots. The main factor consisted of four cropping systems: intercropping ofmaizeand U. brizantha, treated with 0, 50 and 100 g a.e. ha -1 ofglyphosate, andmaize monoculture; and for the intercropping ofmaizeand U. ruziziensis, the doses ofglyphosate applied were 25 and 50 g a.e. ha -1 . The secondary factor consisted of five evaluation periods, with dry mass ofmaizeand forage plants being measured on the day when the herbicide was applied, 15 days after the application, at full tasseling ofmaize, in hard farinaceous grain stage, and at maize harvest. Weed density and dry mass were also evaluated. The intercropping system reduced the density and dry mass production of the weed community, without affecting the maize yield components. Glyphosate suppressed the initial growth of U. brizantha and U. ruziziensis intercropped with maize, at the dose of 100 and 50 g a.e. ha -1 , respectively, without compromising straw (residues) formation.
Fresh corms of Colocasia esculenta were purchased from the local market of Hyderabad. The fresh corms are subjected to peel off their skins. The resultant corms were cut in to pieces dried and made in to flour. The flour was steeped in water at 35ºC for 12 h. The slurry obtained was homogenized for 30 min using commercial blender. The suspension obtained was screened using 150 µm sieve and kept for sedimentation for 24 h. The crude starch was then collected and washed several times with purified water to yield pure starch by centrifugation at 3000 rpm. The purified starch was dried in a hot air oven at 50ºC for 24 h. The yield was~2.07% (w/w). The electron photograph of purified Colocasia esculenta starch is illustrated in Fig. 1. Evaluation of Colocasia esculenta as per monograph
Considering the results obtained in the pre- sent research work, the adaptation of AA test by re- ducing the aging duration from 96h to 48h, and the replacement of the germination test by seedling root length measurement using image analysis could be considered a potential method for maize seed vigor analysis. In general, it reduces the test total duration from eight days, or 192h, to four days, or 96h, which represents approximately 50% of time reduction. Additionally it brings to test the benefits of image analysis, with reproducible results, practical proce- dures and does not involving human error in count evaluations, estimates and measurements (SAKO et al., 2001; HOFFMASTER et al., 2003; HOFFAM- STER et al., 2005 ).According to Barros and Marcos - Filho (1997), Pinto et al. (2007) and Santorum et al. (2013), there is an increasing need for efficient meth- ods to assess the physiological quality of seeds, which enable decision making regarding the collec- tion, processing, storage and marketing of the crop, and the association of AA and SRL tests could be a great alternativeto meet those demands.
EKSF process has been studied for the remediation of soils polluted with different contaminants ( Trellu et al., 2016 ) such as pesticides ( Ribeiro et al., 2011; Gomes et al., 2012; Guedes et al., 2014; Ribeiro et al., 2005 ), hydrocarbons ( Gomez et al., 2009; Alcantara et al., 2010, 2012; Mendez et al., 2012; Lopez-Vizcaino et al., 2014a,b; Mousset et al., 2014; Bocos et al., 2015 ) and heavy metals ( Maturi and Reddy, 2006, 2008 ). In fact, the removal of pesticides using EKSR has become a hot topic ( Jackman et al., 2001; Ribeiro et al., 2005, 2011; Harbottle et al., 2009; Gomes et al., 2012; Rodrigo et al., 2014 ), and even recent works were focussed not only on the ef ﬁciency of EKSF but also on the integration of this tech- nique with other remediation technologies such as bioremediation and permeable reactive barriers ( Trellu et al., 2016 ). In general, removal ef ﬁciencies reported with spiked kaolinite (as model of low permeable soil) show the in ﬂuence of electrode arrangements, ﬂushing ﬂuid and electric ﬁeld. However, the loss of the pollutants by ﬁltration, dragging of superﬁcial water or evaporation have not been clearly stated and these are important points to be capable to control the diffusion of pesticides into the soil ( Jackman et al., 2001; Ribeiro et al., 2005, 2011; Harbottle et al., 2009 ).
of 30 ml/1000 vaccine doses. To evaluate the serum titers of antibodies against Newcastle, samples were collected at 14 days (before the vaccination) of two chicks per experimental unit, totalizing 14 birds per treatment that were individually identified, allowing the subsequent collection at 28 and 35 days by puncturing the ulnar vein. The samples were placed in eppendorf tubes without anticoagulant and centrifuged to obtain serum that was later submitted to immune enzymatic assay with ELISA (Enzyme-Linked Immune sorbent Assay) kit (Purchase et al., 1989).