Days Of Coexistence Research Articles

Behavior and damage potential of the newly emerged pest Myochrous armatus (Chrysomelidae: Eumolpinae) on soybean plants in Brazil

AbstractMyochrous armatus Baly, 1865 (Coleoptera: Chrysomelidae) has expanded its occurrence significantly into soybean‐growing areas of Brazilian Cerrado and became an important early‐season soil pest. Experiments were performed under field conditions from 2020 to 2023 to assess several aspects: (1) population behaviour over crop season and offseason; (2) day/night behaviour during the early stages of soybean plants and (3) injury to plants and potential damage to soybean yield to establish the Economic Injury Level (EIL). Adults of the M. armatus population presented a season‐long abundance during the specific period from late October to January, with major captures in November and December (end of Spring), either inside or on the edge of soybean fields. Weeds and volunteer plants of corn and cotton hosts adults and eggs. These findings suggest an univoltine life cycle. Behavioural assessments revealed that M. armatus does not exhibit a specific day, night or crepuscular behaviour, performing deeds at any time. The majority of insects (40% to 70%) were found in the soil throughout the day and night. Adults feed on soybean plants by scraping or cutting the stem, cotyledon, petiole and apical sprouting. Their preference is initially for the stem and cotyledon (up to 14 days after emergence), and later for the petiole (after 21 days of emergence). After 7 days of coexistence at V1‐V3 soybean stages, we observed a potential yield reduction of 35% for each insect per plant. Dynamic EIL estimations are between 0.4 and 1.9 adults per row metre, depending on the grower productivity expectation, control costs and soybean market value. Our results are fundamental for establishing Integrated Pest Management for M. armatus in soybean and other crop systems.

Weed interference in Marandu palisade grass pastures under renewal or maintenance conditions

ABSTRACT The presence of weeds as a consequence of pasture degradation is one of the main problems facing livestock worldwide. Thus, knowing the interference aspects and the appropriate time for weed management is essential for applying a particular control measure. This research aimed to study the weed interference on the morphostructural and nutritional quality of the Marandu palisade grass in conditions of renewal or maintenance of pasture. The experiments were conducted in a randomized block design, with four replicates and treatments consisted of eight growth periods of coexistence between Marandu palisade grass and weeds (0, 15, 30, 45, 60, 75, 90, and 120 days). Forage grass was characterized at the end of the experimental period, corresponding to 120 days of coexistence, and the main morphostructural and nutritional components were determined. Under the renewal or maintenance process, the weeds interfere in the morphostructural and nutritional quality of pasture areas with Marandu palisade grass. In vitro organic matter digestibility of Marandu palisade grass is negatively influenced by weeds, suggesting that control measures for renewal or maintenance areas should be adopted within 24 and 18 days of coexistence, respectively.

Egeria densa Allelopathy on Microcystis aeruginosa Under Different Light Intensities and Preliminary Insight into Inter-Parameter Relationships

Egeria densa release allelochemicals harmful to other species, including cyanobacteria. Under natural conditions, E. densa and Microcystis aeruginosa can be found in various aquatic systems with different light levels. The effect that the coexistence of E. densa has on M. aeruginosa was tested under different photosynthetically active radiation (PAR) intensities. The growth, chlorophyll-a, oxidative stress, and antioxidant activities of M. aeruginosa were quantified after 7 days of coexistence with E. densa. A control experiment without E. densa was conducted for M. aeruginosa under the same conditions to distinguish the effect of the PAR intensity from the allelopathic effect. The allelopathy of E. densa on M. aeruginosa is significantly influenced by the PAR intensity. PAR intensities lower or higher than the favorable range further suppressed M. aeruginosa under coexistence. Research has revealed that the allelopathic effect of E. densa can be utilized to biologically suppress M. aeruginosa under various light conditions. Strong second-order polynomial distributions between the optical density (OD) and cellular H2O2 content of M. aeruginosa were found for both the control and coexistence conditions. In the practical application of E. densa allelopathy, OD can be adopted as a convenient method to obtain an approximate stress status on M. aeruginosa.

INFLUENCE OF Urochloa brizantha ON THE GROWTH AND NUTRITIONAL ABSORPTION OF TREE SPECIES

Influence of Urochloa brizantha on the growth and nutritional absorption of tree species. The objective of this study was to evaluate the influence of Urochloa brizantha var. Marandu on the growth and accumulation of macronutrients in the leaves of Cordia trichotoma and Guarea guidonia. Seedlings of tree species were transplanted to 18-liter pots and kept free of U. brizantha for three months. After that period, three treatments were adopted that consisted of the control (T0), two plants of U. brizantha per pot (T2) and four plants of U. brizantha per pot (T4). Growth and nutrient accumulation of tree species were evaluated after 84 days of coexistence with U. brizantha. The increment in diameter, of both tree species, leaf area and shoot dry matter of G. guidonia were significantly affected by the presence of U. brizantha, compared to the control. Significant differences were observed for the accumulation of potassium and magnesium in the leaves of C. trichotoma.

Maintenance of the Economic Performance of Eucalyptus in Competition With Weeds

The aim of this study was to evaluate the growth of the hybrid clone Eucalyptus grandis × Eucalyptus urophylla submitted to competition with weeds and determine the period prior to economic loss (PPEL). The experiment was carried out in Ulianópolis, Pará State, Brazil, and consisted of the treatments continuous control and no control of weeds. Weed management was carried out by integrating both mechanical and chemical control. Stem base diameter, height, canopy diameter of eucalyptus plants were measured on the 16th month after planting. Wood volume was estimated by means of a volumetric equation. The treatments continuous control and no control of weeds were compared using the Hotelling’s T2 test and the parameters for PPEL calculation were defined from volume estimation. The treatment continuous control promoted significant gains in eucalyptus growth. PPEL tended to be reduced by 3.8287 and 0.2393 units with the increase of a unit in the price of wood and the increase of planting yield, respectively. For different eucalyptus wood prices, the calculated PPEL ranged from 40 to 161 days of coexistence with weeds.

Management of a leadless pacemaker recall via extraction in a patient with a history of multiple previous device implants

We describe a management strategy of a leadless pacemaker recall (LP) via extraction in a pacemaker-dependent patient with a history of multiple previous device implants. We performed a two-step procedure. First, we implanted a second LP in the right ventricle. Then, 3 days later for concerns about the stability of the newly-implanted device, we retrieved the first LP, 3 years after its original implant. The patient was hemodynamically stable throughout the two procedures and no adverse event occurred in the 3 days of coexistence of the two LPs. Although the limitation of a single case experience, this approach may be taken into consideration when facing similar high-risk cases.

Nutritional Value of Marandú Palisade Grass According to Increasing Coexistence Periods with Weeds

ABSTRACT: This research aimed at evaluating the effect of increasing coexistence periods with weeds on the nutritional components of the forage grass Brachiaria brizantha cv. Marandú under pasture renewal conditions. The experiment was arranged in randomized blocks with four replications, and treatments were represented by eight coexistence periods, namely: 0, 15, 30, 45, 60, 75, 90 and 120 days after seedling emergence. A phytosociologic evaluation was performed on the weed community at the end of the coexistence periods; later, weeds were eliminated by an herbicide formulated with aminopyralid+2,4-D (40+320 g L-1) at 2.5 L ha-1, applied in post-emergence. The fodder plants were evaluated at the end of the experimental period as for leaf-stem ratio, volumetric density of green leaf, volumetric density of total dry matter and main nutritional components, including: crude protein, neutral detergent fiber, ether extract, organic matter and mineral matter, and from this, the total carbohydrate content was calculated. The presence of weeds altered the pasture structure, since it affected negatively the leaf/stem ratio and the volumetric leaf density of B. brizantha. The coexistence also reduced the nutritional components of B. brizantha and determined that control measures should be adopted before reaching 30 days of coexistence between fodder plants and weeds.

The antagonistic action of Trichoderma harzianum strain DGA01 against anthracnose-causing pathogen in mango cv. ‘Carabao’

ABSTRACTThe mechanisms of control and efficacy of Trichoderma harzianum strain DGA01 against anthracnose-causing pathogen Colletotrichum gloeosporioides in mango cv. ‘Carabao’ were examined. The action of DGA01 towards C. gloeosporioides was mycoparasitism and production of metabolites. DGA01 parasitised the pathogen by coiling its mycelia and spores on both artificial media and mango fruit surfaces. DGA01 was a parasitic necrotroph capable of killing C. gloeosporioides in 14 days of coexistence in artificial media. Dipping fruit in conidial suspension (106 mL L−1) of DGA01 significantly decreased the incidence of anthracnose as compared to untreated fruit. Reduction in anthracnose severity was 87.90% showing high antagonistic potential of DGA01 in vivo.

<b>Mycorrhizal association in soybean and weeds in competition

The purpose of this study was to evaluate the effects of mycorrhizal association on the interference of Bidens pilosa, Urochloa decumbens and Eleusine indica on soybean culture in two conditions: a) plants competing without contact with roots of another species; b) with contact between roots. At 60 days after planting, growth, nutrient accumulation and mycorrhizal colonization of soybean and weeds were evaluated. The contact between roots of soybean plant and weed species increased the negative interference effects for both species, with less growth and nutrient accumulation. With the individualization of roots, higher competition occurred for soil resources up to 60 days of coexistence between species. In competition with soybean, Bidens pilosa and Urochloa decumbens stood out in accumulation of most nutrients without differing from when cultivated in monocultivation. The increase of the soybean mycorrhizal colonization was 53, 40 and 33% when in competition with Urochloa decumbens, Eleusine indica and Bidens pilosa species, respectively. A positive interaction occurred for soybean mycorrhizal colonization and competing plants irrespective of weed species or root contact.

Períodos de interferência de maria-pretinha sobre tomateiro industrial

Determinou-se os efeitos da convivência com plantas de maria-pretinha sobre a produtividade do tomateiro industrial, híbrido Heinz 9992, em um experimento com dois grupos de tratamentos: no primeiro, o tomate permaneceu livre da competição (60 mil plantas ha-1 de maria-pretinha) do transplantio até 15; 30; 45; 60; 75; 90; 105 e 120 dias (colheita); no segundo, a cultura permaneceu em competição com a maria-pretinha do transplantio até os mesmos períodos citados. Utilizaram-se blocos casualizados, três repetições e parcelas de quatro linhas. Altura, área foliar e massa seca da parte aérea da maria-pretinha foram obtidas a partir de amostras de dez plantas. A área foliar das plantas de maria-pretinha cresceu até 75 dias de convivência com as plantas de tomate (1.588 dm² planta-1), a altura até 60 dias de convivência (85 cm) e a massa seca da parte aérea até 120 dias de convivência (31,7 g planta-1). As produtividades mais alta (108,6 t ha-1 ou 87,6% da produção total de frutos) e mais baixa (14,2 t ha-1; 59,0%) de frutos maduros de tomate foram observadas quando a convivência entre tomate e maria-pretinha ocorreu respectivamente apenas nos 15 primeiros dias e ao longo de todo o ciclo do tomate. Nestes tratamentos, o peso médio de frutos maduros foi de respectivamente 58,7 e 38,0 g. Verificou-se que cada cm² de acréscimo em área foliar das plantas de maria-pretinha causou uma redução de 0,04 t ha-1 na produção de frutos maduros (PFM) (R² = 0,90), cada centímetro em altura da planta daninha reduziu 0,82 t ha-1 na PFM (R² = 0,78) e cada grama de acréscimo em massa seca de caules e folhas da planta daninha causou uma redução de 2,84 t ha-1 PFM (R² = 0,97). O período anterior à interferência, considerando-se a redução na produtividade do tomate em 5%, foi de 27 dias após o transplantio (DAT) da cultura; o período total de prevenção à interferência foi de 46 DAT e, o período crítico de prevenção à interferência, de 27 a 46 DAT.

Imazapyr root exudation from eucalypt seedlings cultivated in nutritive solution

Imazapyr has been used in Brazilian eucalypt cultivation for the maintenance of clearings and coppicing control in areas undergoing stand reform. However, inquiries have been made as to the final fate of the molecule. Imazapyr root exudation in eucalypt plants was evaluated through a bioassay under greenhouse conditions, by applying different herbicide doses (0.000, 0.375, 0.750, 1.125, and 1.500 kg ha-1 a.i.) on Eucalyptus grandis seedlings derived from vegetative propagation, hydroponically cultivated in 2.500 ml vases. Forty-day-old seedlings of the same clone were used as bioindicators, transplanted to the vases two days after herbicide application. After a period of 13 days of coexistence, the sprayed plants were removed and discarded; ten days later, the visual symptoms of toxicity were evaluated and the total dry biomass (aerial part and roots) of the bioindicators were determined. The lowest herbicide dose (0.375 kg ha-1 a.i.) affected the total biomass and growth, being most evident in the aerial part, with larger I50 for root dry biomass. The E. grandis seedlings exuded imazapyr, and/or its metabolites, in concentrations capable of affecting the growth of plants of the same species.

Efeito da densidade e dos períodos de convivência de Cyperus esculentus na cultura do arroz irrigado

Este trabalho teve o objetivo de analisar o efeito competitivo de Cyperus esculentus sobre o desenvolvimento inicial da cultura do arroz irrigado. O experimento a campo foi conduzido em área de produção de arroz irrigado, na Estação Experimental da Universidade do Tocantins, em Formoso do Araguaia-TO. O delineamento estatístico utilizado foi um fatorial 4 x 5 com quatro repetições, em blocos ao acaso. Os tratamentos constaram de quatro densidades de C. esculentus (25, 50, 100 e 200 plantas m-2 e uma testemunha no limpo) e cinco períodos de convivência com o arroz (15, 25, 35, 45 e 60 dias após a emergência). No final de cada período de convivência foram avaliados: matéria seca, área foliar, número de perfilhos e rendimento da cultura. C. esculentus afetou mais a cultura do arroz irrigado a partir dos 25 dias de convivência. Duzentas plantas de C. esculentus m-2, convivendo por um período de 35 dias, reduziram a produção em 20,11%, representando 17,4 sacas ha-1. A matéria seca, a área foliar e o número de perfilhos por plantas de arroz foram afetados pela presença das plantas daninhas em todos os períodos de convivência, porém a área foliar foi a característica mais influenciada.