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The use of pre-emergent herbicides offers a promising alternative for proper management of difficult-to-control weed species in soybeans, such as white-eye ( Richardia brasiliensis Gomes), a glyphosate-tolerant species, and weeds in the Amaranthus genus (commonly referred to as pigweeds). Here, we aimed at determining whether weed control efficacy and crop selectivity are altered when pre-emergent herbicide applications take place either prior to, or right after crop sowing. To this end, field trials were conducted employing 10 preemergent herbicide treatments (plus an untreated control as well as an untreated, weed-free treatment), replicated four times and sprayed either before, or right after soybean sowing. Results indicate that the actual timing of pre-emergent herbicide spraying relative to soybean sowing significantly changed the weed control efficiency set forth by most herbicide active ingredients tested, with no change to their selectivity to crop plants whatsoever. Some herbicides (e.g. diclosulam, mesotrione, flumioxazin, and a flumioxazin + imazethapyr mixture), however, were equally effective for controlling white-eye and pigweeds regardless of application timing. Moreover, the only herbicide treatments allowing for satisfactory (>70%) control of all target weed species (white-eye, pigweeds, and black oats, Avena strigosa Schreb.) were flumioxazin and a flumioxazin + imazethapyr mixture. Spraying performed after sowing resulted in average yield gains of over 600 kg ha-1 relative to pre-sowing applications, possibly owing to better control of broadleaves. Altogether, this information is useful to soybean producers, as it does not lead to an increase in overall costs; instead, it only affects the timing of entry into the area for pre-emergent herbicide application.

Weed species is one of the factors contributing to grain yield losses due to crop-weed competition. Two of the most common weeds of soybean fields in Brazil are from the Rubiaceae family: Borreria latifolia and Richardia brasiliensis. This study aimed to evaluate the effects of B. latifolia and R. brasiliensis on plant development, yield components, and soybean productivity. Two assays were conducted in a randomized block design with four replications, using a two-level factorial design, in which the first factor consisted of the species B. latifolia and R. brasiliensis and the second factor consisted of the densities 0, 2, 4, 6, 8, 10, and 12 plants m-2. Plant height, leaf area and total chlorophyll in the V6 and R5 stages, number of pods per plant, number of grains per pod, 1000-grain weight, and grain yield loss were evaluated in both cultivars. Grain yield of both soybean cultivars was negatively affected by the interference with B. latifolia and R. brasiliensis. The species B. latifolia was more competitive with soybean when compared to R. brasiliensis, causing higher reductions for all variables. Each B. latifolia plant per square meter is able to reduce the yield of soybean by 3 a 4.4%, while each R.brasiliensis plant reduces yield by 2 a 2.6%. For both species, the reduction in soybean yield due to competition was caused by a decrease in the number of pods per plant, number of grains per pod, and 1000-grain weight.

Spermacoce latifolia, S. verticillata, and Richardia brasiliensis (family Rubiaceae, tribe Spermacoceae) are glyphosate-tolerant weeds in the soybean producing areas of Brazil. The weed shifts to glyphosate-tolerant weeds across soybean-producing areas has shown the need for adoption of practices that conserve the efficacy of glyphosate. This study evaluated the effect of single- and double-knockdown herbicide applications on the control of S. latifolia, S. verticillata, and R. brasiliensis prior to soybean sowing. Trials were designed as a randomized block and treatments were arranged as a factorial. Factor A was three systemic herbicide treatments 10 days before sowing (DBS), while Factor B was three contact herbicide treatments applied 0 DBS (“sow and apply”). The single- and double-knockdown applications were followed by post-emergence applications of glyphosate or 2,4-D + glyphosate when the crop reached three leaves. The efficacy of control of each weed species was visually evaluated 14 days after sowing (DAS), as well as 0 and 28 days after post-emergence application (DAA). The double-knockdown applications generally provided higher levels of control for the target weeds of the Rubiaceae family than the single-knockdown applications. Glyphosate + 2,4-D, glyphosate + 2,4-D + diclosulam or glyphosate + [halauxifen-methyl + diclosulam] followed by glufosinate or paraquat achieved at least 90% of control of S. latifolia and R. brasiliensis, but did not control S. verticillata (

Knowledge of factors that influence the germination process and their interactions allows estimating the initial development of a species in a particular environment and optimizing the weed management decisions. The objectives of this study were to evaluate the effect of environmental factors on the germination and initial growth of the weed species Borreria latifolia, Galianthe chodatiana and Richardia brasiliensis. Five trials were conducted using a completely random experimental design, in factorial design, with five repetitions, each one evaluating effects of temperature, irradiance, aluminum, salinity and pH. The germination was assessed daily, and germination speed index and the length of radicle and epicotyl were determined. Temperatures between 20 and 30 °C maximized final germination and germination speed index of the three species. B. latifolia showed low germination with 15 °C temperature. G. chodatiana and R. brasiliensis did not germinate well at temperatures between 30 and 35 °C. B. latifolia and R. brasiliensis did not germinate in the dark condition, whereas G. chodatiana were indifferent to photoperiod. Seeds from B. latifolia and G. chodatiana were more tolerant to aluminum concentration in the germination than R. brasiliensis, while G. chodatiana were tolerant in germination and early growth. Low NaCl concentration inhibits the seed germination of the three species. B. latifolia showed higher adaptation at low pHs, while the other species at pHs close to neutrality. The responses of the species to environmental factors can be used in the planning of strategies for their management.

Research by title the effect inundation period to summed dominant ratio (SDR) and biomass rice weeds of method SRI (system of rice intensification) in Indonesia. Research have been conducted in the Faculty of Agricultural Land Andalas University, Limau Manih, Padang, from February to May 2018. The study aims to identify noxious weed found in SRI method of paddy cultivation in Indonesia. Weeds that have summed Dominance Ratio (SDR) and the highest biomass in this study is a weed Cyperus rotundus, Scirpus juncoides Roxb., Fimbristylis miliacea (L.) Vahl, Cyperus pedunculatus and Richardia brasiliensis Gomez. Highest weed biomass obtained in the treatment of inundation 3 days old and weed biomass lowest is 15 days long inundation.

Increased use of glyphosate in transgenic soybean areas has selected resistant and tolerant weed species. The aim of this study was to evaluate chemical management strategies for controlling Borreria latifolia and Richardia brasiliensis at pre-emergence (Pre), early post-emergence (Poste) and late post-emergence (Postl). Six experiments were carried out in a completely randomized design with four replicates per treatment in the Pre experiments and three in the Poste and Postl experiments, for each of the species. In the Pre experiments, tests were performed with herbicides imazethapyr, sulfentrazone, chlorimuron, diclosulam, S-metolachlor and saflufenacil. In the Poste experiments, seedlings were sprayed with herbicides bentazon, fomesafen, lactofen, flumioxazin and glyphosate. In Postl experiments, adult plants received glyphosate application associated with herbicides 2,4-D, carfentrazone, imazethapyr, flumiclorac, flumioxazin, sulfentrazone, chlorimuron, saflufenacil and glufosinate, plus three sequential applications with glyphosate only and paraquat/diuron. In the experiments, there was a control treatment without application of herbicides. In the Pre experiments, the plants established at 14 and 28 days after application (DAA) were evaluated. In the Poste and Postl experiments, shoot dry matter evaluation and visual control were performed at 14 and 28 DAA. The herbicides sulfentrazone, S-metolachlor and saflufenacil suppressed the emergence of both B. latifolia as R. brasiliensis; chlorimuron-ethyl and diclosulam were effective only on R. brasiliensis. In Poste, fomesafen, lactofen and flumioxazin reached levels of control over 90% of plants of both species. In Postl, glyphosate associated with carfentrazone, flumiclorac, flumioxazin, chlorimuron-ethyl, saflufenacil, glufosinate, and sequential applications of glyphosate/glyphosate, glyphosate/paraquat+diuron, glyphosate+2,4-D/paraquat+diuron reached levels control higher than 95%. RESUMO: A intensificação do uso do herbicida glyphosate em áreas de soja RR tem selecionado espécies de plantas daninhas resistentes e tolerantes. Objetivou-se neste trabalho avaliar estratégias de manejo químico para o controle de Borreria latifolia e Richardia brasiliensis com aplicações em pré-emergência (Pré), pós-emergência inicial (Pósi) e pós-emergência tardia (Póst) dessas plantas. Foram conduzidos seis experimentos em delineamento inteiramente casualizado com quatro repetições nos experimentos em Pré e três em Pósi e Póst, para cada uma das espécies. Nos experimentos em Pré, foram testados os herbicidas imazethapyr, sulfentrazone, chlorimuron, diclosulam, S-metolachlor e saflufenacil. Em Pósi, foram aplicados bentazon, fomesafen, lactofen, flumioxazin e glyphosate. Em Póst, plantas adultas receberam aplicações de glyphosate associadas a 2,4-D, carfentrazone, imazethapyr, flumiclorac, flumioxazin, sulfentrazone, chlorimuron, saflufenacil e glufosinate, além de três aplicações sequenciais com glyphosate isolado e paraquat/diuron. Nos experimentos havia um tratamento testemunha sem aplicação de herbicidas. Nos experimentos Pré, avaliou-se o percentual de plantas emergidas aos 14 e 28 dias após a aplicação (DAA). Em Pósi e Póst foram avaliados o controle visual aos 14 e 28 DAA e a matéria seca da parte aérea. Os herbicidas sulfentrazone, S-metolachlor e saflufenacil suprimiram a emergência tanto de B. latifolia quanto de R. brasiliensis; chlorimuron e diclosulam foram eficientes somente sobre R. brasiliensis. Em Pósi, fomesafen, lactofen e flumioxazin atingiram níveis de controle superiores a 90% sobre ambas as espécies. Em Póst, a associação de glyphosate com carfentrazone, flumiclorac, flumioxazin, chlorimuron, saflufenacil e glufosinate e as aplicações sequenciais de glyphosate/glyphosate, glyphosate/paraquat+diuron, e glyphosate+2,4-D/paraquat+diuron atingiram níveis de controle superiores a 95%.

One of the herbicides that can be used to control weeds on corn cultivation is the atrazine herbicide. The aim of this study was to determine the effectiveness of atrazine in controlling weeds in corn, to determine whether there was a change in the composition of weeds in corn after application of the atrazine, and to determine whether the use of atrazine herbicide could cause phytotoxicity and inhibit growth and reduce corn yield. Th e research was conducted on farmer's land in Hajimena Village, Natar District, South Lampung Regency and Weed Laboratory, Faculty of Agriculture, University of Lampung from November 2019 to March 2020. The research was arranged in a randomized complete block design (RCBD) with four replications and six treatments, namely the herbicide atrazine dose s of 1,20 kg/ha,1,80 kg/ha, 2,40 kg / ha, 3,00 kg / ha, manual weeding , and control. The results showed that atrazine herbicide doses of 1,20-3,00 kg/ha were effective to contro l of weeds total o n corn area up to 6 weeks after application, atrazine herbicide caused chang e o n weed composition of Richardia brasiliensis bec o me Calopogonium mucunoides at 3 and 6 weeks after application, and the application of atrazine herbicide doses of 1,20–3,00 kg/ha did not cause phytotoxicity , inhibit corn growth , and decrease yields. Keywords : atrazine, weed, herbicide, corn

We aimed with this study to evaluate the potential of oilseed crops planted following soybean, in terms of their ability to inhibit the occurrence of weed species under Brazilian Savannah cropping systems. The long-term experiment was installed in 2010 at Dourados, MS, Brazil, and in completely randomized blocks design with five replications with 12 × 24 m plot size. For three consecutive years (2010/11, 2011/12 and 2012/13), soybeans were planted in all the area by October/November being harvested in February/March, when previously marked plots were planted in April with: (1) radish (Raphanus sativus); (2) rapeseed (Brassica napus); (3) crambe (Crambe abyssinica); (4) winter fallow-no plantation after soybeans. In all years the same crop was repeated at the same plots, with no crop rotation. Phytosociological characterization of weed species was carried out in winter (after oilseeds harvest), pre-planting and post-emergence of soybean for the three years. Relative abundance, frequency and dominance, as well as the importance value for each species, was obtained. Areas were also intra-characterized by the coefficients of Simpson, Shannon-Weiner and Shannon-Weiner’s Evenness Proportion, and areas were compared for species dissimilarity with Jaccard’s presence-only coefficient, by multivariate cluster analysis. Oilseed crops definitely contribute for sustainable weed management as a cultural tool. The most important oilseed crop weeds in the Savannah-like region of Brazil were Amaranthus hybridus, Richardia brasiliensis, Lepidium virginicum, Leonotis nepetifolia and Hybanthus parviflorus. After three years of repetitive crop succession, some weeds were selected, and rotation in Winter is advised at least every two or three years.

Herbicides are usually applied multiple times by growers for season long weed control in Florida citrus (Citrus sp.). Rimsulfuron, a sulfonylurea herbicide has been recently registered for control of certain grasses and broadleaf weeds in citrus. To increase the weed control spectrum and reduce application cost, citrus growers often prefer to tank mix herbicides. Field experiments were conducted in 2010 and 2011 in citrus groves in central Florida to evaluate weed control efficacy and crop safety of rimsulfuron applied alone or in tank mixes with flumioxazin, pendimethalin, or oryzalin. Herbicides were applied sequentially in spring and fall in both years on the same experimental plot. Results suggested that rimsulfuron applied alone controlled >80% broadleaf and grass weeds up to 30 days after treatment (DAT) and was comparable to tank mixing rimsulfuron with pendimethalin or oryzalin; however, control was reduced beyond 30 DAT. Rimsulfuron tank mixed with flumioxazin was the most effective treatment at 30 and 60 DAT that provided, respectively, ≥88% and >75%, control of broadleaf weeds including brazil pusley (Richardia brasiliensis), dog fennel (Eupatorium capillifolium), common ragweed (Ambrosia artemisiifolia), cotton weed (Froelichia floridana), and virginia pepperweed (Virginia virginicum) compared with other treatments. Control of natalgrass (Melinis repens) was higher in all tank mix treatments compared with rimsulfuron applied alone with no difference among tank mix partners. Rimsulfuron tank mixed with pendimethalin or oryzalin had no advantage over rimsulfuron applied alone for control of broadleaf weeds. Among sequential applications, weed control was better after fall herbicide application (August) compared with spring (April) because of residual activity of fall applied herbicides. Rimsulfuron tank mixed with flumioxazin will provide citrus growers with an additional weed control option.

Transgenic glyphosate-resistant soybeans (GRS) have been commercialized and grown extensively in the Western Hemisphere, including Brazil. Worldwide, several studies have shown that previous and potential effects of glyphosate on contamination of soil, water, and air are minimal, compared to those caused by the herbicides that they replace when GRS are adopted. In the USA and Argentina, the advent of glyphosate-resistant soybeans resulted in a significant shift to reduced- and no-tillage practices, thereby significantly reducing environmental degradation by agriculture. Similar shifts in tillage practiced with GRS might be expected in Brazil. Transgenes encoding glyphosate resistance in soybeans are highly unlikely to be a risk to wild plant species in Brazil. Soybean is almost completely self-pollinated and is a non-native species in Brazil, without wild relatives, making introgression of transgenes from GRS virtually impossible. Probably the highest agricultural risk in adopting GRS in Brazil is related to weed resistance. Weed species in GRS fields have shifted in Brazil to those that can more successfully withstand glyphosate or to those that avoid the time of its application. These include Chamaesyce hirta (erva-de-Santa-Luzia), Commelina benghalensis (trapoeraba), Spermacoce latifolia (erva-quente), Richardia brasiliensis (poaia-branca), and Ipomoea spp. (corda-de-viola). Four weed species, Conyza bonariensis, Conyza Canadensis (buva), Lolium multiflorum (azevem), and Euphorbia heterophylla (amendoim bravo), have evolved resistance to glyphosate in GRS in Brazil and have great potential to become problems.

Embora o herbicida glyphosate seja considerado não-seletivo, várias espécies de plantas daninhas apresentam certo grau de tolerância às doses recomendadas. No Brasil, já existem relatos de seleção de espécies de plantas daninhas tolerantes ao glyphosate em áreas com o uso intensivo deste herbicida. Assim, o objetivo desta pesquisa foi avaliar a influência da aplicação repetitiva do herbicida glyphosate sobre a dinâmica do banco de sementes das plantas daninhas tolerantes: Commelina benghalensis, Ipomoea grandifolia e Richardia brasiliensis; e das plantas daninhas suscetíveis: Amaranthus hybridus e Galinsoga parviflora. O experimento foi monitorado durante dois anos em áreas experimentais do Departamento de Produção Vegetal da Escola Superior de Agricultura ''Luiz de Queiroz'' - Universidade de São Paulo, Piracicaba, São Paulo. Partindo de uma densidade de 100 plantas m-2 de cada espécie, o glyphosate foi aplicado periodicamente em pós-emergência sobre as plantas daninhas adultas nas doses de 0, 0,36, 1,44 e 2,88 kg e.a. ha-1. O banco de sementes do solo foi estimado através da avaliação de emergência direta das plântulas e extração física das sementes. O banco de sementes das plantas daninhas tolerantes ao glyphosate teve aumento significativo, principalmente nas menores doses. Por outro lado, o banco de sementes das espécies suscetíveis diminuiu ao longo do tempo mesmo nas menores doses do glyphosate. Na última análise do banco de sementes, as plantas daninhas tolerantes apresentaram, na maior dose de glyphosate aplicada, cerca de 12 milhões de sementes não-dormentes ha-1, ao passo que as suscetíveis apresentaram cerca de 4 milhões de sementes não-dormentes ha-1. Concluiu-se que o uso intensivo do herbicida glyphosate pode ocasionar uma mudança na área, aumentando a freqüência das plantas tolerantes ao longo dos anos.

No ano agrícola 1996/97 foi conduzido, na Fazenda-Escola da Universidade Estadual de Ponta Grossa, em Ponta Grossa-PR, um experimento a campo com o objetivo de determinar o período crítico de prevenção da interferência das plantas daninhas sobre a cultura do feijoeiro-comum (Phaseolus vulgaris), em sistema de semeadura direta, associando esse período com a fenologia da planta. O delineamento experimental utilizado foi o de blocos ao acaso em arranjo fatorial 2 x 8, com quatro repetições. Os 16 tratamentos testados foram resultados da combinação de dois conjuntos de tratamentos de interferência das plantas daninhas: (1) inicialmente em convivência com as plantas daninhas (2) inicialmente sem convivência com as plantas daninhas, em sete estádios fenológicos do feijoeiro - V2, V3, V4, R5, R6, R7 e R8 - e uma testemunha em convivência durante todo o ciclo da cultura. O experimento foi instalado em uma área há oito anos sob plantio direto, com semeadura realizada de acordo com a tecnologia recomendada para a cultura, com adubações no sulco e em cobertura e tratamentos fitossanitários, para que os feijoeiros se desenvolvessem normalmente. O período crítico de prevenção da interferência ocorreu entre os estádios fenológicos V4 e R6, e a interferência das plantas daninhas durante todo o ciclo reduziu em média 71% o rendimento de grãos dos feijoeiros. Com relação à comunidade infestante, as dicotiledôneas representaram 61,3% das plantas daninhas, destacando-se as espécies Bidens pilosa e Richardia brasiliensis, com 30,6 e 16,6%, respectivamente; já as monocotiledôneas representaram 38,7% da comunidade infestante, com destaque para as espécies Digitaria horizontalis e Brachiaria plantaginea, com 23,6 e 14,3%, respectivamente.

Um experimento de campo foi conduzido em Presidente Castelo Branco-PR, com o objetivo de avaliar a seletividade do herbicida azafenidin para a cultura de Eucalyptus camaldulensis, assim como sua eficácia no controle de algumas plantas daninhas infestantes nessa cultura. Azafenidin foi aplicado nas doses de 300, 400, 500 600 e 800 g i.a. ha-1, em pré-emergencia das plantas daninhas. Tratamentos adicionais, incluindo oxyfluorfen (720 g i.a. ha-1), uma testemunha capinada e outra testemunha sem capina, foram também incluídos. Tanto azafenidin quanto oxyfluorfen provocaram sintomas de toxicidade na cultura; no primeiro, as injúrias foram mais intensas em doses ³ 600 g i.a. ha-1. Em relação ao controle de plantas daninhas, doses de azafenidin a partir de 500 g i.a. ha-1 foram efetivas no controle de Brachiaria decumbens, Commelina benghalensis, Richardia brasiliensis e Sida santaremnensis, mesmo 180 dias após a aplicação. Doses menores de azafenidin resultaram em controle suficiente da maioria das plantas daninhas, mas com menor efeito residual.

Objetivou-se com este trabalho estudar a inter-relação entre a cultura de milho e cultivares de Urochloa spp. em consórcio, assim como a interferência de plantas daninhas nesses sistemas. O ensaio foi aleatorizado em três blocos em esquema de parcelas subdivididas, sendo as parcelas constituídas por sete sistemas de produção (Urochloa brizantha cv. 'Marandu' e cv. 'Piatã' e U. decumbens cv. 'Basilisk' em cultivo solteiro e em consórcio com o milho e cultivo solteiro de milho) e as subparcelas pelo controle de plantas daninhas (com e sem capina manual). Verificou-se que o estabelecimento dos consórcios de milho com as cultivares de Urochloa spp. não afeta os componentes de rendimento de produção, altura e produtividade do milho, assim como não reduz a comunidade de plantas daninhas, mas interfere na densidade populacional e massa de matéria seca por planta e por área das cultivares de Urochloa spp. Houve níveis de interferência semelhantes das plantas daninhas entre os sistemas de produção sem capina, devido à similaridade entre suas comunidades de plantas daninhas, com predomínio de espécies consideradas altamente competitivas, como Panicum maximum, e à predominância de espécies como Richardia brasiliensis e Ageratum conyzoides, associadas ao controle com capina. This research was carried out to study the interaction between the corn and Urochloa spp. cultivars in association, as well as the interference of weeds in this cropping system. A randomized experiment in three blocks with split-plots design was conducted. The plots consisted of seven cropping systems (Urochloa brizantha cv. 'Marandu' and cv. 'Piatã' and U. decumbens cv. 'Basilisk' a sole culture and in association with corn as well as the sole culture of corn) and the split-plots by weed control (with and without weeding). It was found that the establishment of corn-Urochloa spp. cultivars association does not affect yield components such as height and grain yield, nor reduces the weed community, but interferes in the density, mass of dry matter per plant and per area of Urochloa spp. cultivars. There were similar levels of interference of weeds between cropping systems without weeding due to the similarity between the weed communities, showing the predominance of species considered as highly competitive such as Panicum maximum and also due to the low infestation with predominance of species such as Richardia brasiliensis and Ageratum conyzoides, associated with weed control.

The effects of competition of six weed species on growth, nutrient concentration and nutrient content of coffee plant root system under greenhouse conditions were evaluated. Thirty days after coffee seedling transplantation into 12 L pots with soil level area of 6.5 dm². Weeds were transplanted or sowed in these pots, at densities of 0, 1, 2, 3, 4 and 5 plants per pot. The duration of competition (or weedy periods) from weed transplantation or emergence until plant harvesting, at the weed preflowering stage, were (in days): 77 (Bidens pilosa), 180 (Commelina diffusa), 82 (Leonurus sibiricus), 68 (Nicandra physaloides), 148 (Richardia brasiliensis) and 133 (Sida rhombifolia). Dry matter of coffee plants was linearly reduced with increasing B. pilosa and S. rhombifolia density, with pronounced effect of B. pilosa. C. diffusa was the only weed species whose increasing density in the pots did not diminish crop root dry matter. L. sibiricus, N. physaloides and R. brasiliensis reduced root dry matter of coffee plants by 75, 52 and 47%, respectively, as compared to the weed-free treatment, regardless of weed density. Under competition, even though weed species showed lower macronutrient concentration in the roots (except for P), they accumulated 4.2 (N), 12.3 (P), 4.3 (K), 5.5 (Ca), 7.6 (Mg) and 4.4 (S) times more nutrients in the roots than the coffee plants. Crop and weed nutrient concentration, as well as competition degrees greatly varied depending on both weed species and densities. Este trabalho teve como objetivo avaliar os efeitos da competição de seis espécies de plantas daninhas sobre o crescimento, a concentração e o conteúdo de nutrientes no sistema radicular de plantas de café, cultivadas em casa de vegetação. Aos 30 dias após o transplantio das mudas de café, em vasos contendo 12 L de substrato e com área de 6,5 dm² na superfície do solo, fez-se o transplantio e, ou, a semeadura das espécies daninhas nesses vasos, em seis densidades (0, 1, 2, 3, 4 e 5 plantas por vaso). Os períodos de convivência, desde o transplantio ou emergência das plantas daninhas até a colheita das plantas, quando do florescimento das plantas daninhas, foram (em dias): 77 (Bidens pilosa), 180 (Commelina diffusa), 82 (Leonurus sibiricus), 68 (Nicandra physaloides), 148 (Richardia brasiliensis) e 133 (Sida rhombifolia). A massa seca do sistema radicular das plantas de café reduziu-se linearmente com o aumento da densidade de B. pilosa e de S. rhombifolia, com efeito mais pronunciado em B. pilosa. C. diffusa foi a única espécie que não reduziu o acúmulo de matéria seca no sistema radicular das plantas de café. L. sibiricus, N. physaloides e R. brasiliensis reduziram a massa seca da raiz do café em 75, 52 e 47%, respectivamente, comparado ao tratamento livre de interferência, independentemente da densidade de plantas daninhas. Sob competição, apesar de apresentarem, no seu sistema radicular, concentrações de macronutrientes (exceto para P) inferiores àquelas do café, as plantas daninhas acumularam 4,2 (N), 12,3 (P), 4,3 (K), 5,5 (Ca), 7,6 (Mg) e 4,4 (S) vezes mais nutrientes nas raízes que as plantas de café. A concentração de nutrientes no café e nas plantas daninhas, assim como o grau de interferência dessas plantas, variaram fortemente com a espécie e densidade de planta daninha.

"In the humid forest regions of southern Cameroon in central Africa, sectoral and macroeconomic policy reforms introduced in the late 1980s have led to intensified land use, which in turn has resulted in, among other environmental consequences, shortened fallow systems dominated by the Asteraceae shrub, Chromolaena odorata (L.) King and Robinson, rather than by secondary forest species. A trial was established to determine the effect of shortened fallow duration and invasion by C. odorata on the weed flora in subsequent mixed food cropping systems. Plots were established in cleared 5- to 7-year-old fallow fields in which the vegetation was either dominated by C. odorata or not, and in which the dominant fallow vegetation in the previous crop-fallow rotation had been either C. odorata, forest, or herbaceous (not dominated by C. odorata). Cassava (Manihot esculenta Crantz), maize (Zea mays L.), and groundnuts (Arachis hypogaea L.) were intercropped and weed species were assessed 6, 14, and 30 weeks after crop planting. Soil analyses were conducted to assess the influence of edaphic traits on the distribution and abundance of dominant weed species. The results clearly indicated an enrichment of the weed flora with time after planting, but little difference between fallow histories. Two groups of weed species corresponded with soil characteristics: C. odorata, Cyathula prostrata, Mariscus alternifolius, Mikania cordata, Musanga cecropioides, and Trema orientalis were preponderant on soils with high clay, N, and C contents, and Ageratum conyzoides, Cyperus sp., Haumania danckelmaniana, Paspalum conjugatum, Pouzolzia guineensis, Richardia brasiliensis, Sida rhombifolia, Stachytarpheta cayennensis, Talinum triangulare, and Triumfetta cordifolia were preponderant on sandier soils with high pH, P, and Mg contents."

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:51:31Z No. of bitstreams: 1 S0100-83582004000100007.pdf: 126510 bytes, checksum: 3dc5be71beca2e6875b03d8716e33819 (MD5) Made available in DSpace on 2013-08-22T18:51:31Z (GMT). No. of bitstreams: 1 S0100-83582004000100007.pdf: 126510 bytes, checksum: 3dc5be71beca2e6875b03d8716e33819 (MD5) Previous issue date: 2004-03-01 Made available in DSpace on 2013-09-30T17:50:09Z (GMT). No. of bitstreams: 2 S0100-83582004000100007.pdf: 126510 bytes, checksum: 3dc5be71beca2e6875b03d8716e33819 (MD5) S0100-83582004000100007.pdf.txt: 31403 bytes, checksum: c94ce296de89434fca52588226830148 (MD5) Previous issue date: 2004-03-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:13:25Z No. of bitstreams: 2 S0100-83582004000100007.pdf: 126510 bytes, checksum: 3dc5be71beca2e6875b03d8716e33819 (MD5) S0100-83582004000100007.pdf.txt: 31403 bytes, checksum: c94ce296de89434fca52588226830148 (MD5) Made available in DSpace on 2014-05-20T13:13:25Z (GMT). No. of bitstreams: 2 S0100-83582004000100007.pdf: 126510 bytes, checksum: 3dc5be71beca2e6875b03d8716e33819 (MD5) S0100-83582004000100007.pdf.txt: 31403 bytes, checksum: c94ce296de89434fca52588226830148 (MD5) Previous issue date: 2004-03-01 Foram realizados dois experimentos, em condições de casa de vegetação, no Departamento de Biologia Aplicada à Agropecuária da FCAV-UNESP de Jaboticabal, objetivando-se determinar o acúmulo de massa seca, assim como a distribuição e o acúmulo de macronutrientes durante os ciclos de vida de plantas de soja cultivar BR16, no período de outubro de 2000 a fevereiro de 2001, e de Richardia brasiliensis (poaia-branca), uma planta daninha de elevada importância para esta cultura no Brasil, especialmente em áreas de plantio direto, no período de outubro de 1998 a fevereiro de 1999. Os estudos foram realizados em delineamento experimental inteiramente casualizado, com quatro repetições. Quatro plantas cresceram em vasos com capacidade de sete litros, preenchidos com areia de rio lavada, peneirada e irrigada diariamente com solução nutritiva. Os tratamentos foram representados pelas épocas de amostragem, realizadas a intervalos de 14 dias, a saber: 22, 36, 50, 64, 78, 92, 106, 120, 134, 148, 162 e 176 dias após a emergência (DAE) das plantas de R. brasiliensis; e 21, 35, 49, 63, 77, 91, 105 e 119 DAE das plantas de soja cv. BR-16 (precoce). em ambas as plantas, as folhas tiveram a maior partição de biomassa durante sete semanas. Para este dado, a partição foi maior para as estruturas reprodutivas em soja e nos caules para a poaia-branca. O ponto de máximo acúmulo teórico de massa seca deu-se aos 104 DAE para a soja (36,6 g por planta) e aos 146 DAE para a poaia-branca (16,4 g por planta). da emergência até aos 50 DAE as folhas apresentaram maior participação no acúmulo de massa seca, nas duas espécies. Após 50 DAE notou-se, em ambas as espécies, uma inversão na representatividade das folhas por caules, para a espécie daninha, e por caules e posteriormente por estruturas reprodutivas, para a cultura. A taxa de absorção diária dos macronutrientes atingiu maiores valores entre 69 e 87 DAE para a soja e entre 106 a 111 DAE para a planta daninha. Levando em conta a média dos valores de pontos de inflexão observados para a cultura da soja, aos 78 DAE uma planta de soja acumula teoricamente 25,9 g de massa seca; 615,5 mg de N; 77,2 mg de P; 538,6 mg de K; 535,0 mg de Ca; 171,5 mg de Mg; e 39,5 mg de S. Para o mesmo período, uma planta de R. brasiliensis acumula teoricamente 3,7 g de massa seca; 50,8 mg de N; 3,2 mg de P; 104,4 mg de K; 127,8 mg de Ca; 18,8 mg de Mg; e 3,7 mg de S. Two greenhouse trials were carried out under greenhouse conditionsat the Department of Agricultural Biology at FCAV-UNESP in Jaboticabal, SP, Brazil to study tbiomass accumulation as well as macronutrient distribution and accumulation during the life cycle of the soybean cultivar BR 16 from October 2000 to February 2001, and Richardia brasiliensis (Brazilian pusley), from October 1998 to February 1999. Brazilian pusley is one of the most important weeds in the mid western soybean growing area, mainly under no tillage system. The studies were conducted in a randomized complete design with four replications. Four plants were grown in seven liter pots filled with sandy substrate irrigated daily with a nutritive solution. The treatments were represented by timing of sampling, performed at 14 day intervals, 22, 36, 50, 64, 78, 92, 106, 120, 134, 148, 162 and 176 days after emergence (DAE) of R. brasiliensis plants; and 21, 35, 49, 63, 77, 91, 105 and 119 DAE of the soybean plants BR-16 (early maturity) For both plants, the leaves had the highest biomass partition during seven weeks. For these data, partition was higher in reproductive structures in soybean and in the stems for Brazilian pusley. The maximumcritical biomass accumulation was estimated at 104 days for soybean (36.6 g plant-1) and at 146 days for R. brasiliensis (16.4 g planta-1). From emergence up to 50 DAE, the leaves presented higher participation in biomass accumulation, in both species. After 50 DAE, it was observed in both species an inversion in leaf representativity per shoots, for the weed species and per shoots and later per reproductive structures, for thecrop. The maximumdaily macronutrient uptake ratewas achieved between 69 and 87 days in soybean and 106 and 111 DAE in R. brasiliensis. Considering of the inflexion point average observed for the soybean culture, it is possible to estimate that, at 78 DAE, this plant theoretically accumulates 25.9 g of dry weight ; 615.6 mg oN; 77.2 mg P; 538.6 mg K; 535.0 mg Ca; 171.5 mg Mg and 39,5 mg S. In the same period, one razilian pusley plant accumulates 3.7 g dry weight; 50.8 mg N; 3.2 mg P; 104.4 mg K; 127.8 mg Ca; 18.8 mg Mg and 3. 7 mg oS. Universidade Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Departamento de Biologia Aplicada à Agropecuária Universidade Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista Faculdade de Ciências Agrárias e Veterinárias Departamento de Biologia Aplicada à Agropecuária

Richardia brasiliensis (Rubiaceae), also known as white eye or ‘poaia-branca’ in Brazil, is an important agricultural weed in the tropics (2). Relatively little is known about diseases affecting this species. In March 2013, all of the plants of this weed species invading an orchid plantation in Nova Friburgo (State of Rio de Janeiro) and a private orchard at Viçosa (State of Minas Gerais) in Brazil were found to bear intense leaf blight symptoms. Lesions were circular to elliptical, 1.4 to 10.5 mm in diameter, grayish to pale brown, and coalesced leading to necrosis of large areas of the leaves. Leaf samples were collected, dried in a plant press, and representative specimens deposited in the local herbarium at the Universidade Federal de Viçosa (Accession Nos. VIC 39759 and VIC 39760). A fungus found in association with diseased tissues was isolated by directly transferring conidia from infected leaves onto PDA plates, and two isolates were deposited in a local culture collection (COAD Accession Nos. 1335 and 1443). Conidia were removed from infected leaves using a scalpel, and mounted in lactophenol and lactofuchsin for observation with a light microscope (Olympus BX 51). Conidiophores were epiphylous, isolated, subcylindrical, straight to slightly curved, 97.5 to 170.0 × 5.0 to 8.0 μm, 2 to 6 septate, unbranched, pale brown and paler towards the apex, and smooth. Conidia were straight to slightly curved, pyriform to obovoid, 35.5 to 43.5 × 12.5 to 25.0 μm, with the apex rounded and the base subacute, 1 to 3 distoseptate, the subterminal cell often dark brown and larger than the other cells (sometimes leading to the distortion and curving of conidia); the other cells were golden brown and the conidia were smooth. The morphology of the fungus on R. brasiliensis was equivalent to that described for Curvularia richardiae (1). Genomic DNA was extracted from a 7-day-old pure culture of both isolates, and the large subunit (LSU) region of ribosomal DNA (rDNA) was amplified with the primers LR0R/LR5 (3). The resulting sequences were deposited in GenBank (KF880800 and KF880801). A BLASTn search revealed 99% similarity of the two isolates from Brazil with the LSU sequence of an isolate of Cochiobolus geniculatus (JN941528). Three healthy, 10-cm-tall R. brasiliensis plants were inoculated with a conidial suspension (1 × 106 conidia/ml) of isolate COAD 1335 until runoff, and the plants kept for 2 days in a dew chamber at 26 ± 3°C. Additionally, two plants were sprayed with distilled water and kept under the same conditions. Six days after inoculation, symptoms appeared on all inoculated plants that were similar to symptoms on plants in the field. Non-treated control plants remained healthy. C. richardiae was isolated from the lesions on inoculated plants. Although there is an incomplete record of a Curvularia sp. associated with seeds of R. brasiliensis in Brazil (4), that record included no description of the fungus or information on a disease caused on the plants. This is the first report of C. richardiae causing a disease on R. brasiliensis in Brazil. Although the fungus was first described in Australia (1), C. richardiae is most likely a native from the neotropics, as is the host plant, R. brasiliensis. The fungus was probably introduced accidentally into Australia on the weedy host but has remained unnoticed in the native range until now. References: (1) J. L. Alcorn. Trans. Brit. Mycol. Soc. 56:155, 1971. (2) R. R. Rosseto et al. Planta Daninha 15:25, 1997. (3) R. Vilgalys et al. J. Bacteriol. 172:4239, 1990. (4) C. Yamashita et al. Fitopatol. Bras. 13:122, 1988.

O presente experimento, inteiramente casualizado, foi desenvolvido em condições de laboratório no Departamento de Defesa Fitossanitária, FCA/UNESP - Botucatu, entre julho e setembro de 1992. Amostras de Areia Quartzosa equivalentes à 40 g de terra seca à 105 oC ± 2 com ou sem adição de 1,9 g de matéria seca de plantas de poaia-branca (Richardia brasiliensis), 0,19 g de nitrogênio (NH4)2SO4 e 0,88 g de apatita de Araxá, foram incubadas no escuro a 25 o C ± 2 , com umidade mantida a 60% da capacidade de retenção de água. Durante a incubação, determinou-se o CO2 liberado, utilizando-se o método de retenção em NAOH seguida de titulometria com HCl; a biomassa microbiana, método de fumigação-incubação; o pH e a quantidade de fósforo extraído por resina. A maior liberação de CO2 ocorreu durante os dez primeiros dias de incubação, com 77% do total de carbono liberado nos tratamentos com adição de poaia, e 37% nos tratamentos sem adição da mesma. A liberação de CO2 foi 57 vezes maior nos tratamentos com poaia em relação ao controle. A poaia também provocou aumentos na biomassa microbiana (média de 8 vezes a biomassa do tratamento controle), e a adição de nitrogênio e/ou fosfato de rocha junto à poaia antecipou os picos de formação de biomassa de 20 para 10 dias de incubação. Os níveis de fósforo disponível foram maiores no tratamento com adição de fosfato de rocha apenas. A poaia também alcalinizou o sistema, não permitindo desta forma, observar-se relação significativa entre pH e teor de fósforo disponível. The present experiment, totally randomized, was carried out under laboratory conditions at the Departamento de Defesa Fitossanitária, FCA/UNESP-Botucatu, between July and September, 1992. Fresh air-dry samples of quartz sand representing 40g of dry soil each, at 105 o C ± 2, with or without addition of 1.90g of dry matter of "poaia-branca" (Richardia brasiliensis) plants, 0.19g of nitrogen (NH4)2SO4 and 0.88g of Araxá apatite, were incubated under dark conditions at 25 oC ±2,with moisture held at 60% water retention capacity. During incubation, CO2-liberation was determined by means of the method of retention in NaOH followed by titration with HCl; microbial biomass was determined through the fumigation-incubation method, while pH and phosphorus extract by resin. CO2-liberation was high during the first ten days of incubation, with 77% of total carbon released in treatments with "poaia" addition, and 37% in treatments without addition. CO2-liberation was 57 times higher in the "Poaia" treatments compared to the control.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:51:20Z No. of bitstreams: 1 S0100-83581999000100007.pdf: 175533 bytes, checksum: 31443c875797b5f9292ea245f6fee7a0 (MD5) Made available in DSpace on 2013-08-22T18:51:21Z (GMT). No. of bitstreams: 1 S0100-83581999000100007.pdf: 175533 bytes, checksum: 31443c875797b5f9292ea245f6fee7a0 (MD5) Previous issue date: 1999-04-01 Made available in DSpace on 2013-09-30T17:48:15Z (GMT). No. of bitstreams: 2 S0100-83581999000100007.pdf: 175533 bytes, checksum: 31443c875797b5f9292ea245f6fee7a0 (MD5) S0100-83581999000100007.pdf.txt: 27734 bytes, checksum: 75f45d270e92865b8cfcba5b990e9924 (MD5) Previous issue date: 1999-04-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:21:21Z No. of bitstreams: 2 S0100-83581999000100007.pdf: 175533 bytes, checksum: 31443c875797b5f9292ea245f6fee7a0 (MD5) S0100-83581999000100007.pdf.txt: 27734 bytes, checksum: 75f45d270e92865b8cfcba5b990e9924 (MD5) Made available in DSpace on 2014-05-20T13:21:21Z (GMT). No. of bitstreams: 2 S0100-83581999000100007.pdf: 175533 bytes, checksum: 31443c875797b5f9292ea245f6fee7a0 (MD5) S0100-83581999000100007.pdf.txt: 27734 bytes, checksum: 75f45d270e92865b8cfcba5b990e9924 (MD5) Previous issue date: 1999-04-01 O presente experimento, inteiramente casualizado, foi desenvolvido em condições de laboratório no Departamento de Defesa Fitossanitária, FCA/UNESP - Botucatu, entre julho e setembro de 1992. Amostras de Areia Quartzosa equivalentes à 40 g de terra seca à 105 oC ± 2 com ou sem adição de 1,9 g de matéria seca de plantas de poaia-branca (Richardia brasiliensis), 0,19 g de nitrogênio (NH4)2SO4 e 0,88 g de apatita de Araxá, foram incubadas no escuro a 25 o C ± 2 , com umidade mantida a 60% da capacidade de retenção de água. Durante a incubação, determinou-se o CO2 liberado, utilizando-se o método de retenção em NAOH seguida de titulometria com HCl; a biomassa microbiana, método de fumigação-incubação; o pH e a quantidade de fósforo extraído por resina. A maior liberação de CO2 ocorreu durante os dez primeiros dias de incubação, com 77% do total de carbono liberado nos tratamentos com adição de poaia, e 37% nos tratamentos sem adição da mesma. A liberação de CO2 foi 57 vezes maior nos tratamentos com poaia em relação ao controle. A poaia também provocou aumentos na biomassa microbiana (média de 8 vezes a biomassa do tratamento controle), e a adição de nitrogênio e/ou fosfato de rocha junto à poaia antecipou os picos de formação de biomassa de 20 para 10 dias de incubação. Os níveis de fósforo disponível foram maiores no tratamento com adição de fosfato de rocha apenas. A poaia também alcalinizou o sistema, não permitindo desta forma, observar-se relação significativa entre pH e teor de fósforo disponível. The present experiment, totally randomized, was carried out under laboratory conditions at the Departamento de Defesa Fitossanitária, FCA/UNESP-Botucatu, between July and September, 1992. Fresh air-dry samples of quartz sand representing 40g of dry soil each, at 105 o C ± 2, with or without addition of 1.90g of dry matter of poaia-branca (Richardia brasiliensis) plants, 0.19g of nitrogen (NH4)2SO4 and 0.88g of Araxá apatite, were incubated under dark conditions at 25 oC ±2,with moisture held at 60% water retention capacity. During incubation, CO2-liberation was determined by means of the method of retention in NaOH followed by titration with HCl; microbial biomass was determined through the fumigation-incubation method, while pH and phosphorus extract by resin. CO2-liberation was high during the first ten days of incubation, with 77% of total carbon released in treatments with poaia addition, and 37% in treatments without addition. CO2-liberation was 57 times higher in the Poaia treatments compared to the control. UNESP FCA Depto de Defesa Fitossanitária UNESP FCA Deptartamento de Defesa Fitossanitária UNESP FCA Departamento de Ciência do Solo UNESP FCA Depto de Defesa Fitossanitária UNESP FCA Deptartamento de Defesa Fitossanitária UNESP FCA Departamento de Ciência do Solo

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:51:18Z No. of bitstreams: 1 S0100-83581997000100003.pdf: 200821 bytes, checksum: 8db9c5eaa6d221b02d3edf2b3c1147f3 (MD5) Made available in DSpace on 2013-08-22T18:51:18Z (GMT). No. of bitstreams: 1 S0100-83581997000100003.pdf: 200821 bytes, checksum: 8db9c5eaa6d221b02d3edf2b3c1147f3 (MD5) Previous issue date: 1997-01-01 Made available in DSpace on 2013-09-30T19:42:22Z (GMT). No. of bitstreams: 2 S0100-83581997000100003.pdf: 200821 bytes, checksum: 8db9c5eaa6d221b02d3edf2b3c1147f3 (MD5) S0100-83581997000100003.pdf.txt: 13481 bytes, checksum: 09950aeb5a1ec5a9f83896dce25cd03d (MD5) Previous issue date: 1997-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:11:09Z No. of bitstreams: 2 S0100-83581997000100003.pdf: 200821 bytes, checksum: 8db9c5eaa6d221b02d3edf2b3c1147f3 (MD5) S0100-83581997000100003.pdf.txt: 13481 bytes, checksum: 09950aeb5a1ec5a9f83896dce25cd03d (MD5) Made available in DSpace on 2014-05-20T15:11:09Z (GMT). No. of bitstreams: 2 S0100-83581997000100003.pdf: 200821 bytes, checksum: 8db9c5eaa6d221b02d3edf2b3c1147f3 (MD5) S0100-83581997000100003.pdf.txt: 13481 bytes, checksum: 09950aeb5a1ec5a9f83896dce25cd03d (MD5) Previous issue date: 1997-01-01 A poaia-branca (Richardia brasiliensis Gomez) é uma das principais plantas que infestam espontaneamente os agroecossistemas na América do Sul e, com freqüência, atingem elevadas densidades populacionais, provocando sérios prejuízos aos agricultores. Nos estudos envolvendo a biologia e o controle de plantas daninhas, a área foliar é uma das mais importantes características a serem avaliadas, mas tem sido pouco estudada porque sua determinação exige equipamentos sofisticados ou utiliza técnica destrutiva. Visando obter equações que permitissem a estimativa da área foliar desta planta daninha utilizando características lineares do limbo foliar, facilmente mensuráveis em plantas no campo, foram estudadas correlações entre a área foliar real e as seguintes características das folhas: comprimento ao longo da nervura principal (C), largura máxima do limbo (L) e o produto CxL. Para tanto, foram mensurados os limbos de 500 folhas coletadas em diversas épocas, locais e culturas, em plantas que apresentavam bom aspecto sanitário e nutricional. Todas as equações, lineares simples, geométricas e exponenciais, permitiram boa estimativa da área foliar (AF) da poaia-branca. do ponto de vista prático, sugere-se optar pela equação linear simples envolvendo o produto Cx L, a qual apresentou o menor QM Resíduo. Assim, a estimativa da área folia r de R. brasiliensis pode ser efetuada pela equação AF= 0.5899 (CxL), com coeficiente de determinação (R2) de valor 0.9886 . Brazilian pusley (Richardia brasiliensis) is one of the most important weeds infesting orchards, crops and pastures in South America. Frequently, their populations are dense enough to promote significant losses to the farmers. In the studies on the biology and control of the weeds, the leaf area determination is fundamental, but commonly requires sophisticated and expensive equipment or destructive techniques. So, the present research was set up aiming to obtain a suitable equation for R. brasiliensis leaf área estimation from the linear leaf measures, such as the leaf length in the mid rib direction (C), the maximum leaf width (L), and the rela tion CxL. The measures were done in 500 leaves collected from plants infesting different places and crops and showing suitable nutritional and health conditions. All the equations, linear, geometric, and exponential, permitted suitable estimates of the R. brasiliensis leaf area (AF). The suggested equations was AF = 0.5899 (CxL), because it is easy to use, showed the smallest Stand Error, and the determination coefficient was high, R2=0.9886. UNESP FCAV UNESP FCAV

No ano agrícola 1996/97 foi conduzido, na Fazenda Escola da Universidade Estadual de Ponta Grossa, em Ponta Grossa, PR, um experimento a campo com o objetivo de determinar o período crítico de prevenção da interferência das plantas daninhas sobre a cultura do feijoeiro-comum, em sistema de semeadura direta, associando este período com a fenologia da planta. O delineamento experimental utilizado foi o de blocos ao acaso em arranjo fatorial 2X8, com quatro repetições. Os 16 tratamentos testados foram resultados da combinação de dois modelos de interferência das plantas daninhas: (1) inicialmente sujo e (2) inicialmente limpo, em sete estádios fenológicos do feijoeiro: V2, V3, V4, R5, R6, R7 e R8 e em uma testemunha. A parcela experimental tinha quatro linhas de 7,00 m de comprimento, espaçadas de 0,45 m, com área útil da parcela de 4,50 m2. O experimento foi instalado em uma área há oito anos sob plantio direto, com semeadura realizada de acordo com a tecnologia recomendada para a cultura, com adubações no sulco e em cobertura e tratamentos fitossanitários para que os feijoeiros se desenvolvessem normalmente. No modelo de interferência inicialmente sujo, se manteve a presença das plantas daninhas com os feijoeiros desde a sua emergência até que os diferentes estádios fenológicos fossem alcançados, quando então foi feito o controle químico das infestantes, mantendo os feijoeiros na ausência das plantas daninhas até a colheita, tendo este modelo uma testemunha sempre suja, enquanto que, para o modelo inicialmente limpo, os feijoeiros foram mantidos livres da presença das plantas daninhas, por meio de controle químico, desde a sua emergência até os diferentes estádios fenológicos e a partir destes, as parcelas foram mantidas com a presença das infestantes até a colheita, tendo este modelo uma testemunha sempre limpa. Foram avaliados o rendimento e seus componentes, as características morfológicas, a matéria seca e a partição da matéria seca dos feijoeiros, a composição específica, matéria seca e densidade das plantas daninhas. O período crítico de prevenção da interferência, ocorreu entre os estádios fenológicos V4 e R6. A interferência das plantas daninhas reduziu em média 71,00% o rendimento de grãos dos feijoeiros, influenciando negativamente os componentes do rendimento, as características morfológicas, matéria seca e partição da matéria seca dos feijoeiros, especialmente para aqueles estádios fenológicos que conviveram com as plantas daninhas por um maior período de tempo, como o estádio V2, bem como para aqueles em que ocorre uma alta atividade metabólica e fotossintética na planta, com grande demanda pelos fatores de competição, estádios R7 e R8. Com relação a comunidade infestante, as dicotiledôneas representaram 61,30% das plantas daninhas, destacando-se as espécies Bidens pilosa e Richardia brasiliensis, com 30,60% e 16,60%, respectivamente; e as monocotiledôneas com 38,70% da comunidade infestante, com destaque para as espécies Digitaria horizontalis e Brachiaria plantaginea, com 23,60% e 14,30%, respectivamente.