Chemical control of different digitaria insularis populations and management of a glyphosate-resistant population

This study aimed to control different populations of Digitaria insularis by glyphosate herbicide, isolated and mixed, besides the combination of methods (chemical and mechanical) to manage resistant adult plants. Three experiments were conducted, one in pots which were maintained under non-controlled conditions and two under field conditions. In the experiment in pots, twelve populations of D. insularis were sprayed with isolated glyphosate (1.44 and 2.16 kg a.e. ha(-1)) and mixed (1.44 and 2.16 kg a.e. ha(-1)) with quizalofop-p tefuryl (0.12 kg i.a. ha(-1)). The treatment of 1.44 kg a.e. ha(-1) of glyphosate plus 0.12 kg a.i. ha(-1) of quizalofop was sufficient for adequate control (>95%) of all populations. Population 11 (area of grain production in Itumbiara, GO) was considered sensitive to glyphosate. Others populations were moderately sensitive or tolerant to the herbicide. In the field, the plants of D. insularis of one of the experiments were mowed and, in the other, there were not. Eight treatments with herbicides [isolated glyphosate (1.44 and 2.16 kg a.e. ha(-1)) and mixed (1.44 and 2.16 kg a.e. ha(-1)) with quizalofop-p-tefuryl at 0.12 kg a.i. ha(-1)), clethodim at 0.108 kg a.i. ha(-1)) or nicosulfuron at 0.06 kg a.i. ha(-1))] were assessed, in combination with or without sequential application of the standard treatment, sprayed 15 days after the first application. The combination of the mechanic control with the application of glyphosate (2.16 and 1.44 kg a.e. ha(-1)) plus quizalofop-p-tefuryl (0.12 kg a.i. ha(-1)) or clethodim (0.108 kg a.i. ha(-1)), associated to the sequential application, was the most effective strategy for the management of adult plants of resistant D. insularis.

Chlorophyll fluorescence in guanandi tree (calophyllum brasiliense) after herbicide application

Chlorophyll fluorescence is currently used as a rapid diagnostic and nondestructive method to detect and quantify damage on the photosynthetic apparatus of leaves on weeds, crops and ornamental/coniferous trees in response to both environmental stress and herbicides. This study aimed to evaluate chlorophyll fluorescence in guanandi plants (Calophyllum brasiliense) after application of different postemergence herbicides. The experiment was performed in a completely randomized design, with six treatments (control, bentazon, sulfentrazone, isoxaflutole, atrazine and glyphosate) and five replications. The herbicide treatments were applied with a stationary sprayer, and electron transport rate (ETR) was subsequently analyzed with OS5p Multi-Mode Chlorophyll Fluorometer. In the monitored period, guanandi plants subjected to atrazine showed higher sensitivity to chlorophyll fluorescence than the other treatments. Although bentazon is a photosystem II inhibitor, it showed no major changes in electron transport for the studied species and in the monitored period. In summary, ETR is a good parameter to evaluate the effect of some herbicides on Calophyllum brasiliense plants.

Imazapyr herbicide efficacy on floating macrophyte control and ecotoxicology for non-target organisms

the aims of this study were to determine imazapyr efficacy for floating macrophyte control and ecotoxicology for non-target organisms. For the floating macrophyte control efficacy tests were used the doses of 0,5; 1,0; 2,0; 2,5; 3,0; 3,5 and 4,0 L ha(-1) and a control with 10 replicates. The acute toxicology for non-target organisms was estimated by lethal concentration 50% (LC50 and EC50). The floating macrophyte control efficacy was over 90%. Imazapyr was classified as moderately toxic for the following biomarkers: L. minor, H. eques, B. rerio, P. caudimaculatus, P. canaliculata, and P. mesopotamicus and lightly toxic for A. caroliniana. Thus, imazapyr herbicide is a tool with great potential to be used on floating macrophyte control (E. crassipes, P. stratiotes e S. molesta) in Brazil and this practice can be evaluated by the use of application biomarkers.

Early growth of common bean cropped over ruzigrass residues

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Weed suppression in the formation of brachiarias under three sowing methods

The success of conservation systems such as no-till depends on adequate soil cover throughout the year, which is possible through the use of cover crops. For this purpose the species belonging to the genus Urochloa has stood out by virtue of its hardiness and tolerance to drought. Aiming ground cover for the no-till system, the objective was to evaluate the establishment of two species of the genus Urochloa, in three sowing methods, in the weed suppression and the sensitivity of these forages to glyphosate. The study design was a randomized block with a 2 x 3 x 3 factorial arrangement, in which factor A was composed of Urochloa ruziziensis and Urochloa hybrid CIAT 36087 cv. Mulato II, factor B was formed by sowing methods: sown without embedding, sown with light embedding and sown in rows, and factor C was composed of three doses of glyphosate (0.975, 1.625 and 2.275 kg ha(-1) of acid equivalent). For determination of weed suppression, assessment of biomass yield and soil cover was performed, by brachiaria and weeds, at 30, 60, 90, 120 and 258 days after sowing. Visual assessment of the desiccation efficiency at 7 and 14 days after herbicide application was performed. It is concluded that embedding Urochloa seeds stands out in relation to sowing in the soil surface. Urochloa ruziziensis is more efficient in the dry weight yield, weed suppression, in addition to being more sensitive to glyphosate herbicide.

Behavior of rr soybeans subjected to different formulations and rates of glyphosate in the reproductive period

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparação entre métodos para determinar o período anterior à interferência de plantas daninhas em feijoeiros com distintos tipos de hábitos de crescimento

Beans grain productivity may be reduced by up to 80% and, therefore, knowing the proper time to control weeds becomes fundamental, his research was conducted in order to determine the period prior to interference (PPI) on bean cultivars of different types'plant growth through distinct approaches: arbitrary level of 5% productivity loss; tolerance level (TL), and the Weed Period Prior to Economic Loss (WEEPPEL). Experimental treatments were constituted of ten periods of coexistence, periods of the crop with the weeds: 0-7; 0-14; 0-21; 0-28; 0-35; 0-42; 0-49; 0-56; 0-97 (harvesting) days after emergency (DAE), and a control plot, weed free for the entire period. The experimental design was of the Random Block Design, with four replications. PPI was obtained in all of the different approaches, and the bean plant type II with indeterminate growth had the lowest times of coexistence.

Supressão de plantas daninhas utilizando plantas de cobertura do solo

This study aimed to evaluate soil cover and the suppressive effect on weeds by different cover crops at different seed densities. The experiments were set up in Votuporanga, state of Sao Paulo, Brazil and in Selviria, state of Mato Grosso do Sul, Brazil, in March 2008, after conventional tillage. The experimental design was a randomized complete block with four replications, using the following cover crops at different seed densities per hectare: Sorghum bicolor: 6, 7 and 8 kg ha(-1), Pennisetum americanum, 10, 15 and 20 kg ha(-1), Sorghum sudanense, 12, 15 and 18 kg ha(-1), hybrid of Sorghum bicolor with Sorghum sudanense: 8, 9 and 10 kg ha(-1), Urochloa ruziziensis: 8, 12 and 16 kg ha(-1). A control treatment with spontaneous vegetation was used. Soybean was sown after the management of cover crops. Dry matter and weed density were evaluated at cutting/harvesting of cover crops. In Votuporanga, another assessment of weed plants was made at 35 days after soybean had been sown. The ground cover provided by cover crops was assessed at the time of desiccation and flowering of soybeans. It was concluded that U. ruziziensis and S. sudanense reduced weed infestations by more than 90% and kept ground cover above 80% by the time of flowering of soybean.

Use of grass carp (ctenopharyngodon idella) as a biological control agent for submerged aquatic macrophytes

This study aimed to evaluate feed preference and control efficacy of grass carp (Ctenopharyngodon idella) on the aquatic macrophytes Ceratophyllum demersum, Egeria densa and Egeria najas. An experiment was carried out at mesocosms conditions with 2,000 liters capacity and water residence time of 2.8 days. C. demersum, E. densa e E. najas biomasses were offered individually with sixty g and coupled in similar quantities of 30 g of each species, evaluated during 81 days, envolving 6 treatments. (1 - C. demersum, 2 - E. najas, 3 - E. densa, 4 - C. demersum + E. najas, 5 - C. demersum + E. densa and 6 - E. najas + E. densa). When offered individually, E. najas and C. demersum presented the same predation rate by grass carp, which was higher than E. densa predation rate. When plants were tested in pairs, the order of feed preference was C. demersum > E. najas > E. densa. E. najas and C. demersum percentage control ranged from 73 to 83%. No relation between biomass consumption and grass carp body weight gain was observed, probably due to differences in nutritional quality among macrophyte species according to fish necessities. Therefore, it is concluded that the use of grass carp is one excellent technique to control submersed macrophytes in Brazil.

Avaliação de pontas de jato plano na deposição da calda de pulverização com diferentes combinações de plantas de feijão, Brachiaria plantaginea e Bidens pilosa

Objetivou-se com este trabalho avaliar a ponta XR na deposição da calda de pulverização com diferentes combinações de plantas de feijão, Brachiaria plantaginea e Bidens pilosa, em dois volumes de aplicação, com e sem a adição de surfatante Silwet. Foi utilizado como traçador o corante Azul Brilhante FDC -1 na concentração de 500 ppm para quantificar a deposição. Os tratamentos constituíram-se de sete combinações de plantas: (feijão), (B. plantaginea), (B. pilosa), (feijão + B. plantaginea), (feijão + B. pilosa), (B. plantaginea + B. pilosa) e (feijão + B. plantaginea + B. pilosa). O delineamento experimental foi o inteiramente casualizado. Foram avaliadas as pontas de jato plano XR 110015 VS e XR 11002 VS com volumes de aplicação de 150 e 200 L ha-1, respectivamente, com e sem a presença do Silwet a 0,05% v v-1. Após a aplicação, as plantas foram imediatamente coletadas e, em seguida, lavadas em 100 mL de água destilada, para posterior quantificação do traçador em espectrofotômetro. As pontas XR apresentaram comportamento distinto na deposição das gotas de pulverização nas espécies estudadas; a adição de um surfatante à calda de pulverização aumentou a uniformidade da deposição nos alvos e contribuiu para a redução do volume de aplicação.

Efeito de extratos de adubos verdes sobre Lactuca sativa e Digitaria horizontalis

Objetivou-se avaliar os efeitos de extratos de quatro espécies de adubos verdes (Canavalia ensiformis, Crotalaria spectabilis, Mucuna aterrimae Sorghum bicolor cv. AG 2005) sobre a germinação de sementes e o crescimento inicial de plântulas deLactuca sativa e de Digitaria horizontalis. Foram realizados dois experimentos: no primeiro, avaliou-se a aplicação das soluções diluídas a 1%, 2%, 3%, 4%, 5% e10% de extratos aquosos da parte aérea e das raízes das espécies de adubos verdes sobre a germinação, índice de velocidade de germinação e o comprimento radicular de L. sativa; no segundo, avaliou-se a incorporação ao solo de 0, 10, 20, 30, 40 e 50 g dm-3 da biomassa dos adubos verdes sobre o acúmulo de massa seca (parte aérea e raízes) e o desenvolvimento radicular de plântulas de L. sativa e de D. horizontalis. Concluiu-se que os extratos aquosos das espécies C. ensiformis, C. spectabilis, M. aterrima e S. bicolor cv. AG 2005 promoveram efeitos negativos sobre a germinação e o IVG das sementes de L. sativa. A incorporação ao solo da biomassa dessas espécies de adubos verdes influenciou negativamente no desenvolvimento inicial das plântulas de L. sativa. Entretanto, verificou-se efeito positivo sobre o desenvolvimento inicial de D. horizontalis com a incorporação ao solo da biomassa de C. spectabilis.

Influência do glyphosate no perfil bioquímico e fisiológico de populações de azevém (Lolium multiflorum) suscetíveis e resistentes ao herbicida

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Interferência intra e interespecífica de Urochloa decumbens e Synedrellopsis grisebachii

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Interferência do caruru-roxo no crescimento e na produtividade da pimenta dedo-de-moça

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Interferência das plantas daninhas na produtividade e na qualidade tecnológica da cana-de-açúcar no manejo cana-crua e queimada

Pós-graduação em Agronomia (Produção Vegetal) - FCAV