Growth inhibition of sourgrass as a function of period of darkness after diquat application

Photosystem-inhibiting herbicides, such as diquat, act by inducing oxidative stress. However, oxidative damage impairs translocation, resulting in regrowth of the plants. The aim was to evaluate the effectiveness of diquat in controlling the growth of sourgrass exposed to different periods of darkness after application of the herbicide, as well as to evaluate the photosynthetic activity and the production of reactive oxygen species. Two experiments (field and greenhouse) were conducted by applying diquat (200 g a.i. ha-1) on sourgrass plants at the 3 to 4 tiller stage. The treated plants were subjected to different periods of darkness after diquat application (0, 1, 2, 3, 4, 5, and 6 h), in addition to the control treatment without any application. Growth inhibition and mass evaluations of the sourgrass plants were performed in both experiments, whereas photosynthetic activity and H2O2 accumulation in the leaves were evaluated in the greenhouse experiment. The results showed an increase in the sourgrass growth inhibition with an increase in the period of darkness after application. There was a need for a minimum of 6 h of darkness after diquat application to fully inhibit growth (100%) of the sourgrass, whereas plants that remained in the sun since application exhibited less than 50% inhibition. The increase in the period of darkness after diquat application resulted in a reduction in photosynthetic activity and, consequently, lower accumulation of H2O2. Thus, the maintenance of sourgrass in the dark for at least 6 h enables total control of the growth of the plants, preventing regrowth.

Sourgrass control in response to the association of 2, 4-d to ACCase inhibitor herbicides / Controle de grama azeda em resposta à associação de 2, 4-d a herbicidas inibidores de ACCase

ACCase inhibitor herbicides are widely used to control poaceae such as sourgrass (Digitaria insularis). However, these herbicides are selective for eudicots, which requires the use of broadleaf herbicides in areas with broadleaf and narrow leaf weeds. The objective of this study was to evaluate the effect of the association ACCase inhibitors and 2,4-D for the control of sourgrass. Two experiments were carried out under greenhouse conditions. The first experiment evaluated the effect of associating 2,4-D and graminicides to control of sourgrass, using dose-response curves for the herbicides clethodim, quizalofop-P-tefuril and clethodim + quizalofop-P-tefuril. In the second experiment, due to the results of the first one, the necessary period between the application of 2,4-D and the graminicides was evaluated in order to avoid antagonism in sourgrass. The results show that the herbicide clethodim, at the recommended dose, has its efficiency reduced in about 8% when applied in association with 2,4-D. As for the herbicide quizalofop-P-tefuril, this effect was higher, causing a reduction of 39% in control. However, the association of 2,4-D to the mixture of clethodim + quizalofop-P-tefuril did not result in antagonism. It takes nine and 12 days between the application of 2,4-D and the graminicides clethodim and quizalofop-P-tefuril, respectively, for there to be no antagonism.

Os herbicidas inibidores da ACCase são amplamente utilizados no controle de poáceas, tal como o capim-amargoso. No entanto, esses herbicidas são seletivos para plantas eudicotiledôneas, o que demanda a utilização de herbicidas latifolicidas, tais como as auxinas sintéticas, em áreas que existam plantas daninhas de folhas largas e folhas estreitas. O objetivo deste trabalho foi avaliar o efeito da associação de inibidores da ACCase e 2,4-D sobre o controle de capim-amargoso. Foram realizados dois experimentos em casa de vegetação. No primeiro experimento foi avaliado o efeito da associação de 2,4-D aos graminicidas no controle de capim-amargoso, utilizando-se curvas de dose-resposta para os herbicidas clethodim, quizalofop-P-tefuril e clethodim + quizalofop-P-tefuril. No segundo experimento, em decorrência dos resultados do primeiro, foi avaliado o período necessário entre a aplicação de 2,4-D e os graminicidas para que não ocorra antagonismo em capim-amargoso. Os resultados demonstram que para o herbicida clethodim, na dose recomendada, a redução de controle foi de cerca de 8% quando o 2,4-D foi aplicado em associação. Já para o herbicida quizalofop-P-tefuril, esse efeito foi superior, causando redução de 39% no controle. Porém, a associação do 2,4-D à mistura de clethodim + quizalofop-P-tefuril não resultou em antagonismo. São necessários nove e 12 dias entre a aplicação de 2,4-D e os graminicidas clethodim e quizalofop-P-tefuril, respectivamente, para que não ocorra antagonismo.

Genetic use restriction technologies and possible applications in the integrated pest management / Tecnologias genéticas de restrição de uso e possíveis aplicações no manejo integrado de pragas

ABSTRACT: Genetic use restriction technologies (GURTs) were developed to preserve the intellectual property of genetically modified crops (GM) and ensure the return of investments made by industry to obtain technology delivered through seeds. The aims of this review are to discuss the GURTs and analyze their possible applications in integrated management of agricultural pests. There are two classes of GURTs: T-GURTs (trait-based GURTs), wherein the generated seed are viable, but the next generation does not express the trait of agronomic interest, and V-GURT (variety-based GURTs), in which plants produce non viable seeds. However, beyond the seed protection purpose, the GURTs could have also other application to solve agronomic problems. One of the most important is the use of GURTs as a tool to restrict gene flow of GM traits to relative weeds. In addition, it is proposed the use of this technology in integrated weed management by preventing the GMs seed germination, which produces volunteer plants that compete with the crop of interest. Also, these volunteer plants may serve as alternative hosts for insects and pathogens in between crop seasons. The GURTs could contribute to the control of undesirable agents in agricultural systems, reducing the use of pesticides and increasing crop yields.

RESUMO: As tecnologias genéticas de restrição de uso (GURTs) foram idealizadas a fim de preservar a propriedade intelectual de culturas geneticamente modificadas (GMs) e garantir o retorno dos investimentos feitos pelas empresas para a obtenção de tecnologias transmitidas via sementes. Os objetivos dessa revisão são discutir as GURTs e analisar suas possíveis aplicações no manejo integrado de pragas agrícolas. Existem duas classes de GURTs: a T-GURT (trait-based GURT), na qual as sementes produzidas são viáveis, porém as plantas da geração seguinte não expressam o caractere de interesse agronômico, e a V-GURT (variety-based GURT), na qual as plantas produzem sementes inviáveis. Contudo, além do propósito da proteção das sementes, o uso de GURTs poderia também ter outras aplicações na resolução de problemas agronômicos. Um dos mais importantes é o uso das GURTs como ferramenta para impedir o fluxo de genes de culturas transgênicas para plantas daninhas coespecificas. Além disso, propõe-se o uso dessa tecnologia no manejo integrado de plantas daninhas, por meio da prevenção da germinação de sementes GMs, que geram plantas voluntárias que competem com a cultura de interesse. Além disso, essas plantas voluntárias podem servir como hospedeiros alternativos para insetos e patógenos nos períodos de entressafra. Dessa forma, as GURTs poderiam contribuir no controle de agentes indesejáveis em sistemas agrícolas, reduzindo a utilização de agrotóxicos e aumentando a produtividade dos cultivos.

Volume de calda e inseticidas no controle de Piezodorus guildinii (Westwood) na cultura da soja / Diferent spray volumes and insecticides in the control of Piezodorus guildinii (Westwood) in soybean crop

Em pulverizações com bicos hidráulicos, o volume de calda é um dos aspectos mais importantes para o sucesso do controle químico de pragas. O objetivo deste trabalho foi avaliar o efeito do volume de calda e inseticidas no controle de Piezodorus guildinii (Westwood), na cultura da soja. Testaram-se os volumes de calda de 50, 100 e 150l ha-1 e os inseticidas endossulfam (437,5g i.a. ha-1) e tiametoxam + lambda-cialotrina (21,15 + 15,90g i.a. ha-1). Tiametoxam + lambda-cialotrina apresentou maior efeito residual e controle de P. guildinii em relação à endossulfam. Esses inseticidas respondem da mesma forma, aumentando a eficiência de controle da praga com o aumento do volume de calda.

The spray volume is one of the most important aspects interfering on the success of pest control. The objective of this study was to evaluate the effects of spray volume on the efficiency of the insecticides in the control of Piezodorus guildinii (Westwood) in soybean crop. Were evaluated the volumes of 50, 100 and 150l ha-1 and the insecticides endosulfan (437.5g a.i. ha-1) and tiametoxan + lambda-cyhalothrin (21.15 + 15.90g a.i. ha-1). Tiametoxan + lambda-cyhalothrin had better residual and control of P. guildinii than endosulfan. Both insecticides showed the same behavior, increasing P. guildinii control with spray volume increasing.