ABSTRACT Sourgrass (Digitaria insularis) is one of the principal weeds in Brazil, and there are reports of its being glyphosate-resistant. The aim of this study was to determine the coexistence period of the TMG7063 IPRO soybean cultivar with a weed community predominated by D. Insularis, with no negative interference on final production (period prior to interference - PPI), as well as to determine the period for which the crop might remain free of such interference (total period of interference prevention) in Brazil. The coexistence and control periods under study were 15, 30, 45, 60, 75, 90, 105, and 120 days after sowing (DAS) the soybean, with the experiment arranged in a randomized block design with four replications. At the end of each coexistence period and at the end of the control-period experiment (single collection), there was an increase in weed density, dry matter, and the relative importance of D. insularis as the coexistence period increased. The number of pods was reduced from 87 (from 120 DAS in the control) to 49 (from 75 DAS for coexistence), and maximum yield was reduced from 5,551.3 kg ha-1 (from 120 DAS in the control) to 3,998.6 kg ha-1 (from 60 DAS for coexistence) due to coexistence with the weed community. The PPI was estimated at nine DAS, with losses of 5.0%. It can be concluded that a weed community predominated by D. insularis reduces soybean yield by up to 59.3%. The ‘TMG 7063 IPRO’ soybean can coexist with a weed community predominated by D. insularis for up to nine days after sowing and tolerate a loss in yield of up to 5%. Digitaria Brazil glyphosateresistant. glyphosateresistant glyphosate resistant. resistant glyphosate-resistant TMG TMG706 D Insularis PPI, , PPI) total prevention 15 30 45 90 105 12 (DAS replications controlperiod single collection, collection collection) density matter increased 8 4 7 coexistence, 55513 5 551 3 5,551. ha1 ha 1 ha- 39986 998 6 3,998. 50 0 5.0% 593 59 59.3% 706 5% TMG70 9 10 5551 55 5,551 3998 99 3,998 5.0 59.3 70 TMG7 555 5,55 399 3,99 5. 59. 5,5 39 3,9 5, 3,

Resumo Plantas de eucalipto são sensíveis à interferência imposta pela comunidade infestante, principalmente durante o crescimento inicial, período que compreende o primeiro ano após a instalação da cultura. Sendo assim, o presente estudo objetivou avaliar o efeito de densidades crescentes de Commelina benghalensis L. (trapoeraba) sobre o crescimento inicial de plantas de Eucalyptus grandis Hill (ex Maiden) em duas estações do ano (inverno e verão). Foram realizados dois experimentos, um no inverno (durante 90 dias) e outro no verão (durante 120 dias), em área aberta, semicontrolada, em caixas de 70 L. Para ambos os experimentos utilizou-se delineamento em blocos casualizados, com quatro repetições e os tratamentos consistiram de densidades crescentes de trapoeraba: 0 (testemunha), 4, 8, 16, 20, 28, 36, 40, 60 e 80 plantas m-2. Quinze dias após o plantio das mudas de trapoeraba, foi plantada uma muda de eucalipto no centro de cada caixa. Ao final dos períodos experimentais, foram avaliados a altura, o diâmetro, a área foliar e a massa seca da parte aérea do eucalipto. Observou-se que a partir de 4 plantas m-2 já houve interferência negativa no crescimento do eucalipto, com reduções de 38,4% na área foliar e 35% na massa seca, no inverno; e reduções de 52,9% na área foliar e 64,7% na massa seca, no período de verão. Conclui-se que a partir da densidade de 4 plantas m-2 há interferência no crescimento do eucalipto e que, no período de verão, a planta daninha apresenta comportamento competitivo mais agressivo, causando maior interferência nas plantas de eucalipto.

Abstract Eucalyptus seedlings are sensitive to the interference imposed by weed community, especially during the initial growth period, which is the first year after crop establishment. Thus, this study aimed at evaluating the effect of increasing densities of Commelina benghalensis L. on the initial growth of Eucalyptus grandis Hill (ex Maiden) plants at two seasons of the year. For this, two experiments were carried out using 70 L boxes in an open and semi-controlled area: one in winter (during 90 days) and another in summer (during 120 days). Both experiments were randomized block designs with four replicates each. The treatments consisted of increasing densities of tropical spiderwort, namely: 0 (control), 4, 8, 16, 20, 28, 36, 40, 60 and 80 plants m-2. Fifteen days after planting the tropical spiderwort seedlings, one seedling of eucalyptus was planted in the center of each box. The height, diameter, leaf area and total dry mass of eucalyptus were evaluated at the end of the experimental periods. Densities from 4 plants m-2 negatively interfered with eucalyptus growth, reducing by 38.4% the leaf area and 35% the dry mass in winter. While in summer, we found reductions of 52.9% in the leaf area and 64.7% in the dry mass. We concluded that the density from 4 plants m-2 interferes with the growth of eucalyptus and that the weed shows a more aggressive competitive behavior in the summer causing greater interference in the eucalyptus.

Resumo Reguladores vegetais e herbicidas atuam e modificam diversos processos metabólicos nas plantas. A aplicação de doses subletais destes compostos pode ser utilizada de modo a modular o desenvolvimento e o crescimento das plantas, um efeito denominado hormesis. Múltiplos estudos têm relatado o efeito promotor de doses subletais de etiltrinexapac no acúmulo de biomassa e na expansão da área foliar de plantas de eucalipto. Até o presente momento, não há recomendação acerca de doses promotoras e/ou inibidoras de processos metabólicos para a cultura do eucalipto. Desta forma, este trabalho teve como objetivo investigar o efeito de doses crescentes de etiltrinexapac no estabelecimento e crescimento inicial de mudas de Eucalyptus urograndis. Etiltrinexapac foi aplicado em doses de 15 a 90 g de ingrediente ativo por hectare (g i.a. ha-1), em duas modalidades, através da pulverização ou da imersão das raízes em solução. As doses de 15 g i.a. ha-1 via pulverização, e 30 g i.a. ha-1 via imersão de raízes, resultaram em efeito positivo no crescimento do clone GG100 de Eucalyptus urograndis, com acréscimos de, respectivamente, 74,6% e 12,8% na massa seca total, em relação à testemunha. As doses de 15 a 90 g i.a. ha-1, via pulverização, resultaram em efeito estimulatório no crescimento do eucalipto. As doses de 15 e 30 g i.a. ha-1, na modalidade imersão das raízes, proporcionaram efeito positivo nas características avaliadas do eucalipto. A dose de 90 g i.a. ha-1 apresentou efeito inibitório ao crescimento do eucalipto na modalidade imersão das raízes, aos 35 dias após a aplicação de etiltrinexapac.

Abstract Plant growth regulators and herbicides can act and modify several metabolic processes in plants. The use of sub-lethal doses of those compounds might modulate the development and growth of plants, an effect known as hormesis. Recent studies reported the stimulatory responses of sub-lethal doses of trinexapac-ethyl on the biomass accumulation and leaf area expansion of eucalypt plants. To date, there is no recommendation regarding promoting or inhibitory doses of such compounds for eucalypt production industry. Thus, this work aims to investigate the effect of trinexapac-ethyl on the establishment and initial growth of Eucalyptus urograndis seedlings. Trinexapac-ethyl was applied at doses varying 15 to 90 g (plus a control treatment) per hectare of active ingredient (g a.i. ha-1) in two application methods: spraying and root immersion. The doses of 15 g a.i. ha-1 through spraying and the 30 g a.i. ha-1 in root immersion resulted in a positive effect on the growth of Eucalyptus urograndis Clone GG100. Total dry biomass increased by 74.6% and 12.8%, respectively, compared to control plants. The spraying of 15 to 90 g a.i. ha-1 of trinexapax-ethyl resulted in a stimulatory effect on the growth of eucalyptus. The doses of 15 and 30 g a.i. ha-1 via root immersion provided a positive effect on the all evaluated characteristics of eucalyptus. The dose of 90 g a.i. ha-1 resulted in an inhibitory effect on eucalyptus growth through root immersion at 35 days after the trinexapac-ethyl application.