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The repeated use of herbicides can lead to the selection of multiple resistance weeds. Some populations of Conyza bonariensis occurring in olive groves from southern Spain have developed resistance to various herbicides. This study determined the resistance levels to 2,4-D, glyphosate, diflufenican, paraquat, and tribenuron-methyl in a putative resistant (R) C. bonariensis population, and the possible non-target-site resistance (NTSR) mechanisms involved were characterized. Resistance factors varied as follows: glyphosate (8.9), 2,4-D (4.8), diflufenican (5.0), tribenuron-methyl (19.6), and paraquat (85.5). Absorption of 14C-glyphosate was up to 25% higher in the susceptible (S) population compared to the R one, but 14C-paraquat absorption was similar (up to 70%) in both populations. S plants translocated more than 60% of both 14C-glyphosate and 14C-paraquat toward shoots and roots, while R plants translocated less than 10%. The R population was able to metabolize 57% of the 2,4-D into nontoxic metabolites and 68% of the tribenuron-methyl into metsulfuron-methyl (10%), metsulfuron-methyl-hydroxylate (18%), and conjugate-metsulfuron-methyl (40%). Among the NTSR mechanisms investigated, absorption and translocation could be involved in glyphosate resistance, but only translocation for paraquat. Proofs of the presence of enhanced metabolism as a resistance mechanism were found for tribenuron-methyl and 2,4-D, but not for diflufenican. This research informs the first occurrence of multiple resistance to five herbicide classes (acetolactate synthase inhibitors, 5-enolpyruvylshikimate-3-phosphate synthase inhibitors, photosystem I electron diverters, photosystem II inhibitors, and synthetic auxin herbicides) in C. bonariensis.

Herbicides have become one of the most widespread weed-control tools in the world since their advent in the mid-20th century [1]. Nowadays, they are still being used in most conventional cropping systems in modern agriculture [2]. Unfortunately, the persistent use of herbicides is being threatened by the spread of herbicide resistance, a fast evolutionary process that took place a few years after their arrival into modern agriculture [2,3]. To safeguard their future use in agriculture, there is great interest in understanding the molecular mechanisms conferring resistance or predisposing weeds toward evolving herbicide resistance. Herbicide resistance is governed by target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms [4]. TSR-based resistance is caused by any gene alteration able to change the interaction with the encoded target protein/enzyme so that the herbicide is not able to sufficiently interfere with it to cause plant death. TSR mechanisms are usually better understood because there is a single well-known target gene, and therefore, they are monogenic [5]. On the other hand, NTSR mechanisms are those not involving the target protein and can decrease the herbicide arriving at the site of action (SoA) into an insufficient amount, so plants can survive; more rarely, any mechanism protecting plants from herbicide damage is also referred as NTSR [5]. NTSR mechanisms are rarely fully understood since they can be quantitative in nature and controlled by several genes (with each gene providing some level of resistance); in other words, NTSR-based resistance can be polygenic [4]. The increase in multiple herbicide resistance to different SoAs, mainly through enhanced metabolism, is of great concern [2]. Multiple herbicide resistance reflects an evolutionary process by which populations or plants can accumulate different resistance mechanisms (TSR and/or NTSR), conferring resistance to several SoAs [6]. Sadly, this process usually occurs because resistance to one SoA provokes switching to another SoA rather than reducing herbicide-selection pressure [7]. Among NTSR mechanisms, enhanced metabolism is the most threatening because, as a generalist mechanism, it can confer cross-resistance to dissimilar herbicide chemistries, even to those never used before [4]. Conversely, TSR is governed by specialist mechanisms, always specific to a single SoA [5]. This Special Issue was focused on the new well-characterized cases of herbicide resistance, both for TSR and/or NTSR (if a molecular basis is reported), as well as studies that identify new gene alterations conferring TSR or the genetic basis involved in NTSR. Both TSR and NTSR can also be divided into different mechanisms depending on their nature. Point mutations, altered expression, or codon deletion of the target-site gene are among the most reported types of TSR mechanisms [5]. NTSR mechanisms usually involve altered patterns of herbicide absorption, translocation, or metabolism. Herbicide-metabolism-based resistances are complex and often involve genes that are members of large gene families, including cytochromes P450 (P450) and Glutathione-S-transferases (GST) [4]. Therefore, this editorial focuses on the nature of the resistance mechanisms of the two major types, TSR and NTSR, described in each of the contributions to this Special Issue. Joel Torra acknowledges support from the Spanish Ministry of Science, Innovation, and Universities (grant Ramon y Cajal RYC2018-023866-I).

Herbicide-resistant weeds have been identified and recorded on every continent where croplands are available. Despite the diversity of weed communities, it is of interest how selection has led to the same consequences in distant regions. Brassica rapa is a widespread naturalized weed that is found throughout temperate North and South America, and it is a frequent weed among winter cereal crops in Argentina and in Mexico. Broadleaf weed control is based on glyphosate that is used prior to sowing and sulfonylureas or mimic auxin herbicides that are used once the weeds have already emerged. This study was aimed at determining whether a convergent phenotypic adaptation to multiple herbicides had occurred in B. rapa populations from Mexico and Argentina by comparing the herbicide sensitivity to inhibitors of the acetolactate synthase (ALS), 5-enolpyruvylshikimate-3-phosphate (EPSPS), and auxin mimics. Five B. rapa populations were analyzed from seeds collected in wheat fields in Argentina (Ar1 and Ar2) and barley fields in Mexico (Mx1, Mx2 and MxS). Mx1, Mx2, and Ar1 populations presented multiple resistance to ALS- and EPSPS-inhibitors and to auxin mimics (2,4-D, MCPA, and fluroxypyr), while the Ar2 population showed resistance only to ALS-inhibitors and glyphosate. Resistance factors ranged from 947 to 4069 for tribenuron-methyl, from 1.5 to 9.4 for 2,4-D, and from 2.7 to 42 for glyphosate. These were consistent with ALS activity, ethylene production, and shikimate accumulation analyses in response to tribenuron-methyl, 2,4-D, and glyphosate, respectively. These results fully support the evolution of the multiple- and cross-herbicide resistance to glyphosate, ALS-inhibitors, and auxinic herbicides in B. rapa populations from Mexico and Argentina.

Weeds that usually grow in non-agricultural areas have become increasingly common invading perennial crops. Species of the genus Filago, in addition to invading Spanish olive groves, have developed certain levels of natural tolerance to the acetolactate synthase (ALS) inhibiting herbicide flazasulfuron. The objective of this study was to determine the level and the mechanism involved in the tolerance to flazasulfuron in Filago pyramidata L., which occurs in olive groves of southern Spain, as well as to identify possible cross- or multiple-tolerances by evaluating alternative herbicides for its control. A population resistant (R) to flazasulfuron and a susceptible (S) one of Conyza canadensis were used as references. The accessions of F. pyramidata presented LD50 values (from 72 to 81 g active ingredient (ai) ha−1) higher than the field dose of flazasulfuron (50 g ai ha−1), being 11–12.5 times more tolerant than the S population of C. canadensis, but less than half the R population (170 g ai ha−1). Enzymatically, F. pyramidata was as sensitive to flazasulfuron (I50 = 17.3 μM) as the S population of C. canadensis. Filagopyramidata plants treated with flazasulfuron, combined with 4-chloro-7-nitro-2,1,3-benzoxadiazole, had a growth reduction of up to 85%, revealing the participation of glutathione-S-transferases in herbicide metabolism. Filagopyramidata presented cross-tolerance to the different chemical groups of ALS inhibitors, except triazolinones (florasulam). Synthetic auxins (2,4-D and fluroxypyr) presented good control, but some individuals survived (low multiple resistance). Cellulose synthesis, 5-enolpyruvylshikimate-3-phosphate, 4-hydroxyphenylpyruvate dioxygenase, protoporphyrinogen oxidase, photosystem I, and photosystem II inhibitor herbicides, applied in PRE or POST-emergence, presented excellent levels of control of F. pyramidata. These results confirmed the natural tolerance of F. pyramidata to flazasulfuron and cross-tolerance to most ALS-inhibiting herbicides. The mechanism involved was enhanced metabolism mediated by glutathione-S-transferases, which also conferred low multiple tolerance to synthetic auxins. Even so, herbicides with other mechanisms of action still offer excellent levels of control of F. pyramidata.

Bioactivity of nine essential oils (EOs) was studied on Anagasta kuehniella eggs in relation to the longevity of females, parasitism and emergence rates and sex ratio in the generations parental, F1 and F2 of Trichogramma galloi in comparison to a trade formulation of Azadirachta indica. There was no F1 and F2 progeny with Zingiber officinale being the most harmful. The greatest reductions in the parasitism rates (57, 43 and 28%) in the parental generation was caused by Allium sativum, Carapa guianensis and A. indica, respectively. In addition, A. sativum reduced the longevity (4.7 days) in the parental generation and emergence (33%) of F1. Tested EOs did not affect the sex ratio in the generations F1 and F2 and emergence in the F2. Allium sativum and Z. officinale were non-selective to T. galloi; while A. indica, C. guianensis and P. nigrum oils may compromise the progeny; therefore, their use must be avoided. Citrus sinensis, Mentha piperita, Origanum vulgare, Syzygium aromaticum and Thymus vulgare were selective to T. galloi, and these EOs are promising for IPM programs.

Glyphosate excessive use is reported in Brazilian citrus orchards, whereas there is speculation about its consequences and the published studies are contradictory and inconclusive. This study aimed to describe the possible harmful effects by simulating glyphosate drift directly to the leaves of ∼4-yr-old citrus plants. As major results, glyphosate doses360 g ae ha

The occurrence of multiple herbicide resistant weeds has increased considerably in glyphosate-resistant soybean fields in Brazil; however, the mechanisms governing this resistance have not been studied. In its study, the target-site and nontarget-site mechanisms were characterized in an Eleusine indica population (R-15) with multiple resistance to the acetyl-CoA carboxylase (ACCase) inhibitors, glyphosate, imazamox, and paraquat. Absorption and translocation rates of 14C-diclofop-methyl14C-imazamox and 14C-glyphosate of the R-15 population were similar to those of a susceptible (S-15) population; however, the R-15 population translocated ∼38% less 14C-paraquat to the rest of plant and roots than the S-15 population. Furthermore, the R-15 plants metabolized (by P450 cytochrome) 55% and 88% more diclofop-methyl (conjugate) and imazamox (imazamox–OH and conjugate), respectively, than the S-15 plants. In addition, the Pro-106-Ser mutation was found in the EPSPS gene of this population. This report describes the first characterization of the resistance mechanisms in a multiple herbicide resistant weed from Brazil.

Fertiactyl® is a foliar fertilizer with the potential to minimize the phytotoxicity effects caused by glyphosate drift in eucalyptus plants. As the interactions of the glyphosate and Fertiactyl® in...

Introducción. El uso continuo de herbicidas, frecuentemente con múltiples aplicaciones durante el mismo ciclo agrícola, provoca el surgimiento de biotipos/poblaciones de malezas resistentes. La resistencia es la capacidad hereditaria de algunos individuos para crecer y reproducirse sexualmente después del tratamiento de un herbicida a dosis de campo letal para los individuos susceptibles de la población (WSSA, 1998). Objetivos. Entender qué es la resistencia a herbicidas, cuáles son los tipos mecanismos que la confieren y la importancia de su caracterización sirven para implementar estrategias de manejo asertivas tanto de prevención como de manejo de la resistencia. Métodos. Los mecanismos que confieren resistencia pueden ser relacionados con el sitio de acción (mutaciones o sobreexpresión del gen que codifica la enzima-objetivo del herbicida) o no relacionados con el sitio de acción (reducida absorción y traslocación, metabolismo, exudación radicular, exclusión celular del herbicida, muerte celular rápida) (Gaines et al., 2020), los cuales son caracterizados por técnicas de biología molecular, pruebas in vivo usando plantas completas, ensayos enzimáticos in vitro, radiológicas ( 14 C), plataformas analíticas (HPLC, LC-MS/MS, GC-MS) entre otras (Dayan et al., 2015; Déyle et al., 2015; Nandula y Vencill, 2015). Resultados y discusión. La identificación de biotipos de malezas resistentes en campo no debe estar relacionado a un mal uso de herbicidas y sí a su falta de eficacia en especies que previamente eran controladas. Conocer el tipo de mecanismos que confieren resistencia a herbicidas en una población de malezas es fundamental para desarrollar estrategias de manejo adecuadas (Beckie and Harker, 2017). Los mecanismos del sitio de acción son gobernados por un solo gen (resistencia monogénica); por lo tanto, una rotación de herbicidas con modo de acción diferente podría ser suficiente para controlar la resistencia. Sin embargo, los mecanismos no relacionados con el sitio de acción son gobernados por múltiples genes (resistencia poligénica) y cada gen contribuye con cierto nivel de resistencia. Además, estos genes también pueden conferir resistencia múltiple a herbicidas con diferentes mecanismos de acción que no fueron previamente utilizados en el área; por lo tanto, además de rotación de herbicidas, se requieren de estrategias de manejo de la resistencia no químicas. Conclusión. Distinguir poblaciones resistentes (identificar el problema) oportunamente a través de prospecciones de campo, pero principalmente, caracterizar los mecanismos de resistencia (diagnosticar la causa) es esencial para elaborar y ejecutar programas de manejo de resistencia eficientes para evitar el aumento de los niveles de resistencia, así como de la selección de resistencia cruzada o múltiple.

Forest plantations represent the fourth largest crop by planted area in Brazil. However, leaf-cutting ants can compromise their establishment and development. Atta and Acromyrmex (Hymenoptera: Form...

The repeated use of herbicides can lead to the selection of multiple resistance weeds. Some populations of

Climate change is one of the biggest global concerns for scientists. Efforts to limit global temperature are still incipient. In Brazil, Higher Education Institutions (HEIs) can play a central role in achieving these efforts. In this sense, the objective is to show the Legacy of the Zero Carbon Program of the Federal University of Viçosa (UFV) for society, science and environment, in 10 years of operation, with a main focus on the ecosystem service related to carbon off-set. A description of the history, emergence and organizational structure of Zero Carbon Program (CZP) was made, based on research carried out over 10 years of activity in the Atlantic Forest in southeastern Brazil. Five main methodological axes have been described to determine the current legacy of the program: (A) GHG Inventory during the Farmer’s Week (FW) at the UFV; (B) GHG neutralization during FW; (C) Development of GHG quantification and neutralization systems; (D) Collection of bibliographic data developed by the CZP; and (E) Survey of sensitized public. The results of the CZP showed that: 4,162 people became aware of the topic of climate change at and 26,186 people at other events; and those 63 scientific studies related were published. A total of 490.64 tCO2eq. GHG emissions were raised during the FW-UFV. Approximately 4,660 trees were planted in a degraded area in southeastern Brazil as a way to neutralize GHG from the event. The CZP presents opportunities for gains from ecosystem services related to responsive carbon management provided to different social actors.

Of the six-glyphosate resistant weed species reported in Mexico, five were found in citrus groves. Here, the glyphosate susceptibility level and resistance mechanisms were evaluated in saltmarsh aster (Aster squamatus), a weed that also occurs in Mexican citrus groves. The R population accumulated 4.5-fold less shikimic acid than S population. S plants hardly survived at 125 g ae ha−1 while most of the R plants that were treated with 1000 g ae ha−1, which suffered a strong growth arrest, showed a vigorous regrowth from the third week after treatment. Further, 5-enolpyruvylshikimate-3-phosphate basal and enzymatic activities did not diverge between populations, suggesting the absence of target-site resistance mechanisms. At 96 h after treatment, R plants absorbed ~18% less glyphosate and maintained 63% of the 14C-glyphsoate absorbed in the treated leaf in comparison to S plants. R plants metabolized twice as much (72%) glyphosate to amino methyl phosphonic acid and glyoxylate as the S plants. Three non-target mechanisms, reduced absorption and translocation and increased metabolism, confer glyphosate resistance saltmarsh aster. This is the first case of glyphosate resistance recorded for A. squamatus in the world.

Continuous use of glyphosate in citrus groves in the Gulf of Mexico region has selected for resistant Parthenium hysterophorus L. populations. In this study, the target-site and non-target-site resistance mechanisms were characterized in three putative glyphosate-resistant (GR) P. hysterophorus populations, collected in citrus groves from Acateno, Puebla (GR1 and GR2) and Martinez de la Torre, Veracruz (GR3), and compared with a susceptible population (GS). Based on plant mortality, the GR populations were 9.2-17.3 times more resistant to glyphosate than the GS population. The low shikimate accumulation in the GR population confirmed this resistance. Based on plant mortality and shikimate accumulation, the GR3 population showed intermediate resistance to glyphosate. The GR populations absorbed 15-28% less 14C-glyphosate than the GS population (78.7% absorbed from the applied) and retained 48.7-70.7% of 14C-glyphosate in the treated leaf, while the GS population translocated ~68% of absorbed herbicide to shoots and roots. The GR3 population showed the lowest translocation and absorption rates, but was found to be susceptible at the target site level. The 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene sequence of the GR1 and GR2 populations showed the Pro106-Ser mutation, conferring 19- and 25-times more resistance in comparison to the GS population, respectively. Reduced absorption and impaired translocation conferred glyphosate resistance on the GR3 population, and contributed partially to the resistance of the GR1 and GR2 populations. Additionally, the Pro-106-Ser mutation increased the glyphosate resistance of the last two P. hysterophorus populations.

A database on the performance of native plants under different environmental conditions can improve the selection of species most suitable for carbon offset programs. The objective of this work was to identify the potential of 25 tree species for carbon offsetting in a degraded area in the Brazilian Atlantic Forest, with a scoring system based on the survival rate (SV) and average annual carbon increment (IMAC). The diameter and height of trees were measured to estimate the annual increments to select those to be scaling by species by the non-destructive method, and to estimate the volume and carbon of each plant by species. The mean SV of trees was 47% with high variability ranging from 5 to 100%, especially for Schinus terebinthifolius (100%); Sapindus saponaria (95%); Senna multijuga (80%); Handroanthus chrysotricha (80%); Plathymenia foliolosa (75%); Cassia grandis (75%) and Colubrina glandulosa (60%), all pioneers except for H. chrysotricha and C. grandis. The lowest SV were for Caesalpinia peltophoroides (20%); Tibouchina granulosa (10%); Anadenanthera pavonina (5%); Cariniana legalis (5%); Samanea inopinata (5%) and Syzygium jambos (5%), all non-pioneering species, except for A. pavonina. The growth of non-pioneer species was generally lesser than pioneer ones, except for Ceiba speciosa. Among non-pioneers, T. granulosa, Bombacopsis glabra and C. grandis stood out for the hight growth. None of the species reached a maximum score (10 points) for the sum of the parameters considered. The highest scores (nine points) were for Schizolobium parahyba and S. multijulga, both pioneers. The lowest scores (two points) were for A., Cariniana legalis, Lecythis pisonis, Samanea Inopinata and S. jambos followed by Cedrela fissilis, Caesalpinia peltophoroides, Cytharexyllum myrianthum, Hymenaea courbaril, Psidium guineense and Tibouchina granulosa (three points) and Anadenanthera macrocarpa and Sterculia chicha (four points). The methodology adopted allowed the assessment on of the potential of plant species for carbon offsetting projects in degraded areas, specifically in the Brazilian Atlantic Forest.

Amaranthus palmeri S. Watson is probably the worst glyphosate-resistant (GR) weed worldwide. The EPSPS (5-enolpyruvylshikimate-3-phosphate-synthase) gene amplification has been reported as the major target-site-resistance (TSR) mechanism conferring resistance to glyphosate in this species. In this study, TSR and non-target-site-resistance (NTSR) mechanisms to glyphosate were characterized in a putative resistant A. palmeri population (GRP), harvested in a GR soybean crop from Argentina. Glyphosate resistance was confirmed for the GRP population by dose-response assays. No evidence of TSR mechanisms, as well as glyphosate metabolism, was found in this population. Moreover, a susceptible population (GSP) that absorbed about 10% more herbicide than the GRP population was evaluated at different periods after treatment. The GSP population translocated about 20% more glyphosate to the remainder of the shoots and roots at 96 h after treatment than the control, while the GRP population retained 62% of herbicide in the treated leaves. This is the first case of glyphosate resistance in A. palmeri involving exclusively NTSR mechanisms.

Short-spike canarygrass (Phalaris brachystachys (Link.)) from Iranian wheat fields has developed resistance to acetyl-coenzyme A carboxylase (ACCase) inhibitors due to a target-site mutation (Ile-1781-Thr). Target-site resistance mutations may confer pleiotropic effects in weeds. In this paper, the possible effect of the Ile-1781-Thr mutation on the ecological fitness during life cycles in P. brachystachys plants was investigated. ACCase genes of P. brachystachys populations resistant (R) and susceptible (S) to ACCase inhibitors were sequenced and the vegetative growth and reproductive characteristics of the plants were assessed. In the final growth stage (217 days after planting—DAP), R sub-population plants were 30 cm taller than the S plants. Additionally, the R sub-population produced up to 12 leaves and 2.8 tillers more per plant, and accumulated double the dry weight (2850 g m−2) compared to the S sub-population. The leaf area index (LAI) of the R sub-population was 1.1 times higher than that of the S sub-population. In addition, the net assimilation rate (NAR) and plant growth rate (PGR) between 114 and 182 DAP of the R sub-population were 0.11 and 13 g m−2 d−1 higher than the S sub-population, but the relative growth rate (RGR) was similar between R and S sub-populations. The number of spikes (6 vs. 3.8), the spike length (8.4 vs. 5.5), and number of seeds per plant (1276 vs. 751 seed plant−1) of the R sub-population were higher than the S ones, but the weight (3.25 g) and size (11.6 mm2) of 1000 seeds were similar between populations. The R sub-population of P. brachystachys exhibited higher plant growth and reproductive parameters than the S one, which may increase the frequency of resistance in the population in the absence of adequate weed-control methods.

Atta and Acromyrmex are the main genera of leaf-cutting ants present in North and South America, causing extensive damage to agroforestry. Control of the ants requires high handling costs with few effective methods available to decrease the losses. The symbiosis between the leaf-cutting ants and the fungus Leucoagaricus gongylophorus is essential for ant nest survival. Therefore, L. gongylophorus may be a key target in controlling leaf-cutting ants, since its reduction may cause an imbalance in the symbiosis necessary to maintain the nest. Among the options for natural fungal control, plant species are considered important sources of compounds belonging to several classes of natural products that show potential as antifungal agents. This review also presents studies that establish that the antagonist fungi from the Escovopsis and Trichoderma genera effectively reduce the development of L. gongylophorus. The development of nanostructured delivery systems, which have shown advantages over conventional formulations, is suggested for ant control; no commercial nanotechnology-based product has yet been developed, and this appears to be a new approach for future studies.

Since glyphosate was classified as potentially carcinogenic by the International Agency for Research on Cancer, public debate regarding the environmental impact and health risks from its use has intensified. Almost all regulatory agencies throughout the world have concluded that the judicious use of glyphosate does not pose risks to the environment and human health. However, on the last day of 2020 the Mexican government decreed a ban of this herbicide beginning January, 2024. In current Mexican agriculture there are no safer chemical and/or other weed management technologies that allow for the economical substitution of glyphosate for weed control. Many Mexican weed scientists agree that glyphosate use should be reduced, but not banned outright. This decree could have more negative economic and social consequences as well as environmental and human health risks than benefits, which could compromise the country's food and public security. Crop yields are projected by some to decline by up to 40% with this ban, increasing food prices, making food less accessible to low-income consumers. In addition, a black market for the smuggling and illegal sale of glyphosate is possible. The possible environmental, economic and social impacts caused by the glyphosate ban in Mexico are discussed, emphasizing on weed management. This article is protected by copyright. All rights reserved.

The occurrence of multiple herbicide resistant weeds has increased considerably in glyphosate-resistant soybean fields in Brazil; however, the mechanisms governing this resistance have not been studied. In its study, the target-site and nontarget-site mechanisms were characterized in an

Fertiactyl

Eleusine indica is a highly competitive and difficult-to-control plant in annual and perennial crops. In Colombia, broad-spectrum herbicides, such as paraquat and glyphosate, have begun to present poor levels of control for this weed. The multiple resistance to glyphosate and paraquat, the increase in herbicide performance with adjuvants (Retenol&reg, and Trend&reg, 90), and alternative herbicides were evaluated in a resistant (R) population of E. indica collected in rice fields, which is rotated with herbicide-resistant (HR) crops. Based on plant mortality, the R population was 9.8 and 7.2 times more resistant than susceptible (S) plants to glyphosate and paraquat, respectively. R plants accumulated 4.2 less shikimic acid and had at least 70% less electrolyte leakage than S plants when they were exposed to glyphosate and paraquat, respectively. Both adjuvants increased the foliar retention of herbicides. In addition, adjuvants also increased the performance of glyphosate effectiveness between 22% and 58% and that of paraquat from 61% to 100%. Alternative herbicides (atrazine, clethodim, imazamox, diuron, flazasulfuron, glufosinate, oxyfluorfen, quizalofop, and tembotrione) provided high levels of control in both populations of E. indica. This is the first case of multiple resistant E. indica confirmed in Colombia. Adjuvants improved the leaf retention and efficacy of glyphosate and paraquat. In summary, the alternative herbicides evaluated in this study should be adopted by Colombian farmers and provide additional herbicide modes-of-action to combat future resistance.

An integrated weed management system is perfectly aligned with the aim of producing healthy and environmentally sustainable vegetables. This integrated management is fundamental for vegetables, more than in other crops, due to its high commercial value, intensive culture, lack of competitiveness and low availability of registered herbicides. The integration of available weed control methods with a long-term strategy based on preventive and agronomic (cultural) practices is necessary to obtain a desired level of control, decrease the accumulation of the weed seed bank, increase weed diversity and decrease herbicide dependence and minimize their negative impacts. Thus, this book provides essential and updated subjects of information regarding the general characteristics of herbaceous vegetables, critical periods of control, main weeds in the crop, integrated management methods (preventive, cultural, physical, mechanical, biological and chemical); and it is intended for professors, researchers, extensionist, undergraduate and graduate students, rural producers and other professionals involved in the area of weed science.

Background: Coffee and livestock degrade Seasonal Semideciduous Forests in the Zona da Mata region of the Atlantic Forest biome in Brazil. The floristic composition must be studied to preserve and conserve forest remnants. The objective was to evaluate the arboreal structure, characterize the seed dispersal syndrome and the ecological group of forest species of a 45-year-old restored area in Viçosa, Minas Gerais state, Brazil. The phytosociological parameters density, frequency, dominance and importance value, Shannon's diversity and Pielou's equability were evaluated considering individuals with DBH (diameter at breast height) ≥ 5 cm in sixteen contiguous plots (25 x 25 m). Results: A total of 1,323 individuals from 109 species and 35 botanical families were registered, of which 90 were native and 15 exotic species. The importance value (VI= 11.9%) was highest for Guarea guidonia (Fabaceae). The Shannon's diversity (H') was 3.46 and the equability (J') was 0.74. The number of species (33%) was largest for the initial secondary successional class and the number of individuals with zoochoric dispersion syndrome for the late secondary class (38.3%). The basal area was 44.1 m² ha-1 and the average height was 13 m (ranging from 2 to 32 m). Conclusion: The restored Semideciduous Seasonal Forest is in an advanced successional stage with zoochoric species and a great number of late secondary species.

Climate change will be an additional issue to the challenge to manage herbicide resistant weeds. This work investigated the impact of three temperature regimes (10/5, 20/15 and 30/25 °C) on the efficacy, foliar retention, absorption and translocation of fomesafen, protoporphyrinogen oxidase (PPO) inhibitor, and imazamox, acetolactate synthase (ALS) inhibitor, between two Euphorbia heterophylla populations, one susceptible (S) and one multiple PPO and ALS resistant (R). The R population went from 5 (fomesafen) and 12 (imazamox) times more resistant than the S population at 10/5 °C to more than 100 times to both herbicides at 20/15 and 30/25 °C. Leaf retention of fomesafen was not affected by temperature; however, imazamox retention was less at 10/5 and 20/15 °C than at 30/25 °C, and the R population always retained less imazamox than the S population. 14C-fomesafen absorption was similar between populations, but lower amounts were absorbed at 10/5 °C regardless of the evaluation time. Recovered 14C-imazamox rates decreased in both populations as the evaluation time increased, ranging from 82 to 92% at 6 h after treatment (HAT), and from 47 to 76% at 48 HAT, depending on the temperature regime. The 14C-imazamox losses were greater from 24 HAT in R plants grown at 30/25 °C and in all temperature regimes at 48 HAT. Although both populations translocated large amounts of imazamox, the S population distributed it in the rest of the plant (33%) and roots (15%), while the R population kept it mainly on the treated leaf (24%) or lost ~20% more herbicide than S population at 48 HAT, indicating the need for further studies on root exudation between these populations. Low temperatures reduced resistance levels to fomesafen and imazamox in E. heterophylla, suggesting that temperature influences the expression of the mechanisms that govern this multiple resistance.

Different Lolium species, common weeds in cereal fields and fruit orchards in Chile, were reported showing isolated resistance to the acetyl CoA carboxylase (ACCase), acetolactate synthase (ALS) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) inhibiting herbicides in the late 1990s. The first case of multiple resistance to these herbicides was Lolium multiflorum found in spring barley in 2007. We hypothesized that other Lolium species may have evolved multiple resistance. In this study, we characterized the multiple resistance to glyphosate, diclofop-methyl and iodosulfuron-methyl-sodium in Lolium rigidum, Lolium perenne and Lolium multiflorum resistant (R) populations from Chile collected in cereal fields. Lolium spp. populations were confirmed by AFLP analysis to be L. rigidum, L. perenne and L. multiflorum. Dose-response assays confirmed multiple resistance to glyphosate, diclofop-methyl and iodosulfuron methyl-sodium in the three species. Enzyme activity assays (ACCase, ALS and EPSPS) suggested that the multiple resistance of the three Lolium spp. was caused by target site mechanisms, except the resistance to iodosulfuron in the R L. perenne population. The target site genes sequencing revealed that the R L. multiflorum population presented the Pro-106-Ser/Ala (EPSPS), Ile-2041-Asn++Asp-2078-Gly (ACCase), and Trp-574-Leu (ALS) mutations; and the R L. rigidum population had the Pro-106-Ser (EPSPS), Ile-1781-Leu+Asp-2078-Gly (ACCase) and Pro-197-Ser/Gln+Trp-574-Leu (ALS) mutations. Alternatively, the R L. perenne population showed only the Asp-2078-Gly (ACCase) mutation, while glyphosate resistance could be due to EPSPS gene amplification (no mutations but high basal enzyme activity), whereas iodosulfuron resistance presumably could involve non-target site resistance (NTSR) mechanisms. These results support that the accumulation of target site mutations confers multiple resistance to the ACCase, ALS and EPSPS inhibitors in L. multiflorum and L. rigidum from Chile, while in L. perenne, both target and NTSR could be present. Multiple resistance to three herbicide groups in three different species of the genus Lolium in South America represents a significant management challenge.

Background Conventional crossing of soft wheat cultivars resistant to imazamox and glufosinate resulted in two (Rados and Helter) lines resistant to both herbicides. Stacked traits conferring this dual herbicide resistance in these lines, compared with a susceptible (S) cultivar, were characterized. Results Rados and Helter lines were ∼ 18-fold more resistant (R) to glufosinate, and between 15.1 and 19.8-fold more resistant to imazamox than the S cultivar. Resistance to glufosinate and imazamox decreased up to 12% and 50%, respectively, when the herbicides were applied sequentially. The basal activities of the acetolactate and glutamine synthases were similar between R and S plants. Rados and Helter lines were 11.7- and 17.7-fold more resistant to imazamox than the S cultivar, due to the Ser653-Asn mutation in their imi-ALS genes. R lines, susceptible to glufosinate at the target site level, showed lower ammonia accumulation evidencing the activity of the phosphinothricin acetyl transferase. Absorption and translocation patterns for 14 C-imazamox and 14 C-glufosinate were similar between R and S cultivars and so do not contribute to resistance. Conclusion Stacked traits conferring dual herbicide resistance to the lines Rados and Helter come from the resistant parents. These R lines are potential tools for weed management in wheat production, mainly via herbicide rotation. © 2018 Society of Chemical Industry.

Wild mustard (Sinapis arvensis L.) is a weed that frequently infests winter wheat (Triticum aestivum L.) fields in Golestan province, Iran. Tribenuron-methyl (TM) has been used recurrently to control this species, thus selecting for resistant S. arvensis populations. The objectives were: (1) to determine the resistance level to TM of 14 putatively resistant (PR) S. arvensis populations, collected from winter wheat fields in Golestan province, Iran, in comparison to one susceptible (S) population; and (2) to characterize the resistance mechanisms and the potential evolution of cross-resistance to other classes of acetolactate synthase (ALS)-inhibiting herbicides in three populations (AL-3, G-5, and Ag-Sr) confirmed as being resistant (R) to TM. The TM doses required to reduce the dry weight of the PR populations by 50% were between 2.2 and 16.8 times higher than those needed for S plants. The ALS enzyme activity assays revealed that the AL-3, G-5, and Ag-Sr populations evolved cross-resistance to the candidate ALS-inhibiting herbicides from the sulfonylureas (SU), triazolopyrimidines (TP), pyrimidinyl-thiobenzoates (PTB), sulfonyl-aminocarbonyl-triazolinone (SCT), and imidazolinones (IMI) classes. No differences in absorption, translocation, or metabolism of [14C]TM between R and S plants were observed, suggesting that these non-target mechanisms were not responsible for the resistance. The ALS gene of the R populations contained the Trp-574-Leu mutation, conferring cross-resistance to the SU, SCT, PTB, TP, and IMI classes. The Trp-574-Leu mutation in the ALS gene conferred cross-resistance to ALS-inhibiting herbicides in S. arvensis from winter wheat fields in Golestan province. This is the first TM resistance case confirmed in this species in Iran.

The use of chemical insecticides and non-selective natural products authorized for use in organic farming may reduce the effectiveness of egg parasitoids. The side-effects of ten plant essential oils on immature stages of Trichogramma pretiosum were evaluated. Carapa guianensis, Origanum vulgare and Zingiber officinalle during the F1 generation, and Azadirachtin and Mentha piperita in the F2 generation were slightly harmful (class II: 30–79%) to the emergence of this parasitoid. All essential oils affected the longevity of females of the F1 and F2 generations. Thymus vulgaris and Z. officinalle were the oils most harmful to female longevity. Carapa guianensis proved slightly harmful (class II: 30–79%) to parasitism in the F1 generation when applied during the egg-larval and pre-pupal stages and O. vulgare in the F1 generation in the pre-pupal stage alone, of this parasitoid. The sex ratio was lower than 0.5 during the pre-pupal stage of the F1 generation with Azadirachtin, C. guianensis, O. vulgare, Piper nigrum and Syzigium aromaticum, but this parameter was not affected for the other biological stages of T. pretiosum in the F1 and F2 generations. The Azadirachtin, C. guianensis, M. piperita, O. vulgare, T. vulgaris and Z. officinalle oils revealed a mild toxic effect to the immature stages of T. pretiosum and, therefore, it should be used according to patterns of ecological selectivity. Allium sativum and Citrus sinensis essential oils were not harmful to T. pretiosum, and can be used in Integrated Pest Management.

BACKGROUND Susceptibility and the mechanism (s) governing tolerance/resistance to glyphosate were characterized in two putative-glyphosate-resistant Chloris barbata populations (R1 and R2), collected in Persian lime orchards from Colima State, Mexico, comparing them with one non-treated population (referred to as S). RESULTS Glyphosate doses required to reduce fresh weight or cause mortality by 50% were 4.2–6.4 times higher in resistant populations than in the S population. The S population accumulated 4.3 and 5.2 times more shikimate than the R2 and R1 populations, respectively. There were no differences in 14C-glyphosate uptake between R and S populations, but the R plants translocated at least 12% less herbicide to the rest of plant and roots 96 h after treatment. Insignificant amounts of glyphosate were metabolized to aminomethyl phosphonate and glyoxylate in both R and S plants. The 5-enolpyruvylshikimate-3-phosphate synthase gene of the R populations contained the Pro106-Ser mutation, giving them a resistance 12 (R2) and 14.7 (R1) times greater at target-site level compared with the S population. CONCLUSION The Pro106-Ser mutation governs the resistance to glyphosate of the R1 and R2 C barbata populations, but the impaired translocation could contribute to the resistance. These results confirm the first case of glyphosate resistance evolved in this species. © 2018 Society of Chemical Industry

At present, appearance of herbicide resistant weeds is not new because repeated herbicide treatments per agricultural year/cycle are usual in both perennial and annual crops worldwide. Characterizing resistance mechanisms implied in each herbicide resistant weed is the best tool and the basis to develop integrated weed management (IWM) strategies. The main resistance mechanisms which confer low sensibility to glyphosate in a previously confirmed glyphosate-resistant Chloris radiata population (ChrR), occurring in Colombian rice fields, were characterized. Pure line selection by clone plants showed high resistance levels in ChrR. Comparing with GR50 and LD50 values, ChrR was 9.6 and 10.8 times more resistant with respect to a representative susceptible population (ChrS). The nontarget site mechanisms reduced glyphosate absorption and translocation did not contribute to the glyphosate resistance of the ChrR population. However, enzyme activity assays and DNA sequencing demonstrated that at least one target-site resistance mechanism is involved in such resistance. All ten ChrR plants tested had the amino acid substitution Pro-106-Ser. The results may be crucial to decrease the resistance distribution of C. radiata in Colombia by implementing IWM programs. The change in weed control strategies in rice fields from Colombia must include herbicides with different mode of action from glyphosate and non chemical methods to preserve the useful life of glyphosate longer for weed control in the country.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Outra Agência Essential oils from botanical extracts used for insect pest control should be both effective and have low impact on natural enemies. The objective was to evaluate the effects of ten essential oils on the biological and reproductive parameters in two Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) generations. The emergence F1 generation of T. galloi was reduced by more than 30% with Allium sativum, Carapa guianensis, Citrus sinensis, Neem and Syzygium aromaticum. Zingiber officinale reduced the T. galloi emergence of the F1 and F2 generations by between 30 and 99%. The longevity of the F1 generation was reduced by more than 50% with Z. officinale at the pre-pupae and pupae stages. All oils reduced the parasitism rate of the F1 generation in the egg-larva and pre-pupa stages. Allium sativum, C. guianensis and C. sinensis, Neem and Origanum vulgare reduced parasitism by between 30 and 79%. Zingiber officinale was slightly and moderately harmful to the F1 and F2 generations, respectively, for the T. galloi parasitism. The sex ratio of the two T. galloi generations was not affected by the essential oils. The low side effects of the oils on the F2 generation, except for Z. officinale (the most harmful oil), suggest that T. galloi developed some post-transgenerational tolerance/resistance mechanisms to these oils and/or their components. The A. sativum, C. guianensis, C. sinensis, Neem, O. vulgare, S. aromaticum and Z. officinale oils were not selective for T. galloi. Mentha piperita, Piper nigrum and Thymus vulgaris essential oils can be included in integrated pest management programs for this parasitoid.

Premix or tank mix of glyphosate and 2,4-D are a good alternative to control glyphosate-resistant and -tolerant weeds; however, the combination of herbicides may increase the environmental impacts, since mixtures often have higher toxicity than a single herbicide. In addition, antagonism between these herbicides has also been reported. We compared the efficacy of a premix glyphosate+2,4-D formulation with respect to the tank mix of both herbicides on glyphosate-resistant Conyza canadensis and -tolerant Epilobium ciliatum populations in laboratory and field experiments. 2,4-D suppressed the glyphosate-resistance/tolerance of both species, whose populations presented similar responses to their susceptible counterparts (LD50 ≥ 480+320 g ha−1 glyphosate + 2,4-D, respectively). Plants of both species treated with the premix formulations retained ∼100-μL more herbicide solution, accumulated 20–25% and 28–38% more shikimate and ethylene, respectively, and presented greater 14C-glyphosate absorption and translocation, depending on the species, compared to plants treated with the tank mix treatment. Although doubling the field dose (720 + 480 g ha−1) improved (5–22%) the control of these weeds in the field, split applications of both premix and tank mix provided the best control levels (≤70%), but premix treatments maintained control levels above 85% for longer (120-d). No antagonism between glyphosate and 2,4-D was found. The addition of 2,4-D controlled both broadleaf species. For all parameters evaluated on the C. canadensis and E. ciliatum populations in the laboratory and in the field, the premix treatments showed better performance than the tank mix treatments. Premix formulations could reduce the environmental impact of herbicides used to control glyphosate resistant/tolerant weeds by decreasing the herbicide amount needed to achieve an acceptable weed control level.

Dominican farmers have started to apply synthetic auxin herbicides (SAHs) as the main alternative to mitigate the impacts of the occurrence of glyphosate-resistant (GR)

Multiple resistance to acetolactate synthase (ALS, EC 2.2.1.6) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19) inhibitor herbicides was studied in two populations of Conyza canadensis (RTG and STG) harvested in southern Spain. Dose-response and enzymatic activity studies for the ALS-inhibiting herbicides showed only cross-resistance to sulfonylureas group but not to the other ALS chemical groups in the RTG population. Regarding glyphosate, the dose-response studies showed that the RTG population was 11.8 times more resistant than the STG population, while the inhibition of EPSPS enzyme (I50) was similar for both populations. Altered/reduced absorption and translocation were the main resistance mechanisms for glyphosate but not for tribenuron-methyl. The metabolic studies to find differences in the amounts of metabolites between the two populations were carried out using thin layer chromatography (for tribenuron-methyl) and capillary electrophoresis (for glyphosate). Metabolites were significantly differed among the two populations for tribenuron-methyl but not for glyphosate. The sequencing of the target-site ALS gene from RTG plants revealed a single point mutation, Pro-197-Ala, that causes resistance to sulfonylurea herbicide in C. canadensis.

Influence of low temperatures on the glyphosate efficacy was studied in glyphosate-resistant (R) and -susceptible (S) Conyza sumatrensis biotypes. For this purpose, the physiological and enzymatic aspects involved were characterized under two growing temperature regimes [high (30/20 °C) and low 15/5 °C temperatures day/night]. The R biotype was 5.5 times more resistant than the S biotype at high temperatures; however, this R-to-S ratio decreased to 1.6 at low temperatures. At 96 h after treatment (HAT), the shikimic acid accumulation was higher in the S biotype in both temperature regimes (4.6 and 1.9 more shikimic acid at high and low temperatures, respectively), but the accumulation of the R biotype increased 2.6 times at low temperatures compared to high ones. From 24 to 96 HAT, the

Glyphosate is a cheap herbicide that has been used to control a wide range of weeds (4&ndash, 6 times/year) in citrus groves of the Gulf of Mexico, however, its excessive use has selected for glyphosate-resistant weeds. We evaluated the efficacy and economic viability of 13 herbicide treatments (glyphosate combined with PRE- and/or POST-emergence herbicides and other alternative treatments), applied in tank-mixture or sequence, to control glyphosate-resistant weeds in two Persian lime groves (referred to as SM-I and SM-II) of the municipality of Acateno, Puebla, during two years (2014 and 2015). The SM-I and SM-II fields had 243 and 346 weeds/m2, respectively, composed mainly of Bidens pilosa and Leptochloa virgata. Echinochloa colona was also frequent in SM-II. The glyphosate alone treatments (1080, 1440, or 1800 g ae ha&minus, 1) presented control levels of the total weed population ranging from 64% to 85% at 15, 30, and 45 d after treatment (DAT) in both fields. Mixtures of glyphosate with grass herbicides such as fluazifop-p-butyl, sethoxydim, and clethodim efficiently controlled E. colona and L. virgata, but favored the regrowth of B. pilosa. The sequential applications of glyphosate + (bromacil + diuron) and glufosinate + oxyfluorfen controlled more than 85% the total weed community for more than 75 days. However, these treatments were between 360% and 390% more expensive (1.79 and 1.89 $/day ha&minus, 1 of satisfactory weed control, respectively), compared to the representative treatment (glyphosate 1080 g ae ha&minus, 1 = USD $29.0 ha&minus, 1). In practical and economic terms, glufosinate alone was the best treatment controlling glyphosate resistant weeds maintaining control levels &gt, 80% for at least 60 DAT ($1.35/day ha&minus, 1). The rest of the treatments, applied in tank-mix or in sequence with glyphosate, had similar or lower control levels (~70%) than glyphosate at 1080 g ae ha&minus, 1. The adoption of glufosiante alone, glufosinate + oxyfluorfen or glyphosate + (bromacil + diuron) must consider the cost of satisfactory weed control per day, the period of weed control, as well as other factors associated with production costs to obtain an integrated weed management in the short and long term.

Brazil must restore 12 million hectares of degraded areas by 2030 to meet its goal of the Paris Global Climate Agreement (PGCA). In view of this, the development of mixed planting projects related to carbon-offset in degraded areas is increasing, which demonstrates environmental and social responsibility of corporate and governmental organizations. Despite the great potential of mixed restoration plantations to mitigate climate change, Brazil must overcome major challenges in achieving the ratified goals of the PGCA as well as the effectiveness of its carbon-offset projects. In this context, this study has focused on the evaluation of the growth and survival of tree species in a carbon-offset plantation from a degraded area in southeastern Brazil. Five-hundred-and-nine seedlings (15 forest species) were planted in a completely randomized design. Diameter at the soil level and height of individuals were measured at 40 months. Three individuals of each species were selected and was scaling by a non-destructive method. Timber volume was estimated from the sum of the volume of the sections of the individuals, obtained by the Smalian formula. The average annual carbon increment of the individuals was estimated by the equation adjusted from the Schumacher & Hall model. The potential of carbon-offset of the tested plants was evaluated from the SP and μC analysis. The REML (Restricted Maximum Likelihood)/BLUP (Best Linear Unbiased Prediction) method was used to predict μC values for species ordering with carbon -offset potential. Survival was 47.54% at 40 months. The carbon stock of the planting was 2.60 ± 6.2 Kg C individual−1, and the average annual increase in carbon (AAIC) was 0.78 Kg C individual−1year−1. The AAIC value was lower than the average value stipulated for carbon-offset projects (6.0 Kg CO2 individual−1 year−1). Pioneer species contributed more to carbon storage than non-pioneer species.