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The evolution of glyphosate resistance (GR) in weeds is an increasing problem. Glyphosate has been used intensively on wild poinsettia (Euphorbia heterophylla L.) populations for at least 20 years in GR crops within South America. We investigated the GR mechanisms in a wild poinsettia population from a soybean field in southern Brazil. The GR population required higher glyphosate doses to achieve 50% control (LD50) and 50% dry mass reduction (MR50) compared to a glyphosate susceptible (GS) population. The ratio between the LD50 and MR50 of GR and GS resulted in resistance factors (RF) of 6.9-fold and 6.1-fold, respectively. Shikimate accumulated 6.7 times more in GS than in GR when leaf-discs were incubated with increasing glyphosate concentrations. No differences were found between GR and GS regarding non-target-site mechanisms. Neither population metabolized glyphosate to significant levels following treatment with 850 g ha-1 glyphosate. Similar levels of 14C-glyphosate uptake and translocation were observed between the two populations. No differences in EPSPS expression were found between GS and GR. Two target site mutations were found in all EPSPS alleles of homozygous resistant plants: Thr102Ile + Pro106Thr (TIPT—mutation). Heterozygous individuals harbored both alleles, wild-type and TIPT. Half of GR individuals were heterozygous, suggesting that resistance is still evolving in the population. A genotyping assay was developed based on the Pro106Thr mutation, demonstrating high efficiency to identify homozygous, heterozygous or wild-type EPSPS sequences across different plants. This is the first report of glyphosate-resistant wild-poinsettia harboring an EPSPS double mutation (TIPT) in the same plant.

Wild poinsettia (Euphorbia heterophylla L.) is an important weed species in southern Brazil, especially due to the evolution of multiple herbicide resistance (e.g., acetolactate synthase (ALS)- inhibitors, protoporphyrinogen oxidase inhibitors, and glyphosate). The mechanism of resistance to imazamox was investigated in two wild poinsettia populations (R1 and R2) from southern Brazil and compared to a known susceptible (S) population. Imazamox dose-response experiments revealed high levels of resistance: 45-fold and 224.5-fold based on dry biomass reduction, for R1 and R2, respectively. Extremely high concentrations of imazamox (20,000 µM) were not sufficient to provide 50% inhibition of ALS enzyme activity (I50) for R1 or R2. Hence, resistance levels were estimated to be greater than 123-fold for both populations based on in vitro ALS assays. The ALS gene from all R1 and R2 plants had a Trp574Leu mutation. A genotyping assay was developed to discriminate resistant and susceptible alleles based on the Trp574Leu mutation.

To optimize the use of pesticides, several countries have carried out periodic inspections in agricultural sprayers. In Brazil, knowing the conditions of this machinery canguide researches and investments in guidelines for its use and maintenance. The objective of this study was to verify the state of sprayer maintenance used in the North of the state of Paraná, in Brazil. Several sprayer items were evaluated, such as: presence, status and scale of the manometer, status of the hose, status of the anti-drip component, presence of leaks, status of the bar, status of the filters, state of the spraying nozzles and errors in the targeted flow rate. Machines were named as approved when there was no failure in any item evaluated. The factor that caused the biggest level of reprove among the machines was incorrect scale of manometers, which reproved 84.55% of the machines evaluated. Other outstanding factor was the incorrect flow rate in 75.5% of the tested machines. Only one unit was approved from the total of 110 evaluated sprayers.Para a otimização no uso de agroquímicos, vários países têm realizado inspeções periódicas em pulverizadores agrícolas. No Brasil, o conhecimento do estado destas máquinas pode nortear pesquisas e investimentos em orientação de uso e de manutenção das mesmas. O objetivo deste trabalho foi verificar o estado de manutenção de pulverizadores em uso para a região norte do Estado do Paraná. Foram avaliados itens como: presença, estado e escala do manômetro, estado das mangueiras, estado dos antigotejadores, presença de vazamentos, estado da barra, estado dos filtros, estado das pontas de pulverização e erros na taxa de aplicação. As máquinas foram caracterizadas como aprovadas quando não havia falha em nenhum item avaliado. O fator que ocasionou o maior índice de reprova entre as máquinas foi a escala incorreta do manômetro, que reprovou 84,55% das máquinas avaliadas. Outro fator de destaque foi a taxa de aplicação incorreta em 75,5% das máquinas. Do total dos 110 pulverizadores avaliados,apenas uma unidade foi aprovada.

Uma das práticas agrícolas mais eficientes para o controle de plantas daninhas na agricultura é o uso de herbicidas seletivos. Todavia, a aplicação de um mesmo herbicida, ou de herbicidas com o mesmo mecanismo de ação, durante anos consecutivos, na mesma área, pode resultar na seleção de biótipos de plantas daninhas resistentes a esses herbicidas. Com o objetivo de confirmar a resistência de um biótipo (E-298) da planta daninha amendoim-bravo (Euphorbia heterophylla) aos herbicidas inibidores da enzima ALS, encontrado em área de cultivo de soja, no município de Cafelândia, PR, foi conduzido um experimento em área pertencente à Embrapa Soja, Londrina, PR. As plantas provenientes da população com suspeita de resistência foram tratadas com diversos herbicidas e doses, e comparadas com plantas de uma população suscetível de amendoim-bravo. Os tratamentos foram estabelecidos considerando as doses recomendadas dos herbicidas, metade delas e, duas, quatro e oito vezes superiores a recomendada. Os produtos e as doses aplicadas foram cloransulan nas doses 0,0; 0,015; 0,03;0,06; 0,12; 0,24 kg i.a./ha, mais o espalhante adesivo Agral 0,2% v/v, imazetaphapyr nas doses 0,0; 0,05; 0,1; 0,2; 0,4 e 0,8 kg i.a./ha, imazaquin nas doses 0,0; 0,075; 0,15; 0,3; 0,6; 1,2 kg i.a./ha, mais o espalhante adesivo Assist 0,3% v/v, sulfentrazone nas doses 0,0; 0,3; 0,6; 1,2; 2,4; 4,8 kg i.a./ha, mais o espalhante adesivo Assist 0,3% v/v, e lactofen nas doses 0,0; 0,082; 0,165; 0,33; 0,664; 1,329 kg i.a./ha. O biótipo resistente apresentou diferentes níveis de resistência cruzada entre os herbicidas cloransulan, imazethapyr e o imazaquin, e as relações médias de GR50 obtidas foram > 6,85; 11,90 e > 7,18, respectivamente. As curvas de dose-resposta do biótipo resistente apresentaram valores inferiores ao biótipo suscetível, em todas as doses estudadas para os herbicidas cloransulan, imazethapyr e imazaquin. Para os herbicidas sulfentrazone e lactofen, que apresentam mecanismo de ação diferente da inibição da enzima ALS, ocorreu alto índice de controle de ambos os biótipos de amendoim-bravo avaliados, principalmente, nas maiores doses, provando a não existência de resistência múltipla nesse biótipo de amendoim-bravo estudado.One of the most efficient methods of weed control in agriculture is the use of selective herbicides. However, repetitive use of the same herbicide or herbicides having the same mechanism of action, has led to the appearance of weed biotypes which have developed resistance. Thus, an experiment was carried out at Embrapa Soja, in Londrina, Paraná State, Brazil, in order to confirm whether or not there has been resistance of the weed E. heterophylla to the ALS inhibitor herbicides which had been sprayed for several years in a soybean field where the grower has observed failure of the weed control by the ALS inhibitor herbicides. The suspected resistant plants (E-298) from Cafelândia county, Paraná, Brazil, were treated with various doses of several herbicides, compared to a known susceptible biotype. The herbicides and its doses were cloransulan 0,0; 0,015; 0,03; 0,06; 0,12; 0,24 kg a.i./ha, plus Agral 0,2% v/v, imazetaphapyr 0,0; 0,05; 0,1; 0,2; 0,4 e 0,8 kg a.i./ha, imazaquin 0,0; 0,075; 0,15; 0,3; 0,6; 1,2 kg a.i./ha, plus Assist 0,3% v/v, sulfentrazone 0,0; 0,3; 0,6; 1,2; 2,4; 4,8 kg a.i./ha, plus Assist 0,3% v/v and lactofen 0,0; 0,082; 0,165; 0,33; 0,664; 1,329 kg a.i./ha.The results indicated different patterns of cross resistance to cloransulan, imazethapyr and imazaquin; and the GR50 ratios were 97.74; 11.90 and 10.86, respectively. The dose response curves of the resistant biotype presented lower values than the susceptible biotype in all the studied rates for the herbicides cloransulan, imazethapyr and imazaquin. On the other hand, there was no difference in the control between the resistant and susceptible biotypes when sulfentrazone and lactofen were sprayed. It was observed efficient control, mainly with the highest rates of both herbicides, proving that there is no multiple herbicide resistance of the wild poinsettia studied.