Alberto Leão de Lemos Barroso

Qualidade fisiológica de sementes de soja tratadas com inseticidas sob efeito do armazenamento

Dentre os conceitos modernos de controle de pragas, o uso de inseticidas no tratamento de sementes constitui-se num dos metodos mais eficientes. Deve-se, entretanto, conhecer a influencia desses produtos com relacao a qualidade fisiologica das sementes tratadas. Objetivou-se atraves desta pesquisa avaliar a qualidade fisiologica de sementes de soja tratadas com inseticidas, sob quatro periodos de armazenamento (0, 15, 30 e 45 dias apos o tratamento). O delineamento experimental foi o inteiramente casualizado, em esquema fatorial 4 x 7, com quatro repeticoes, onde as sementes do cultivar M-SOY 6101 foram tratadas com os inseticidas thiamethoxam (Cruiser 700 WS), na dose de 250 mL de produto comercial (p.c.)/100 kg de sementes; fipronil (Standak), na dose de 150 mL de p.c./100 kg de sementes; imidacloprid (Gaucho FS), na dose de 150 ml de p.c./100 kg de sementes; [imidacloprid + thiodicarb] (CropStar FS), na dose de 0,3 L. ha-1; carbofuran (Furadan 350 TS), na dose de 1,5 L/100 kg de sementes; acefato (Orthene 750 BR), na dose de 1 kg/ 100 kg de sementes e uma testemunha, sem tratamento. As variaveis analisadas foram: germinacao, velocidade de emergencia, comprimento de raiz e de plântula e porcentagem de plântulas normais no teste de envelhecimento acelerado. A aplicacao dos inseticidas carbofuran e acefato e prejudicial a qualidade fisiologica das sementes de soja cultivar M-SOY 6101, por um periodo de armazenamento de ate 45 dias. A reducao da qualidade fisiologica das sementes, condicionada pelos inseticidas avaliados, intensifica-se com o prolongamento do armazenamento das sementes tratadas, recomendando-se, portanto, que o tratamento inseticida das sementes seja realizado proximo ao momento da semeadura.

Atividade residual de herbicidas pré-emergentes aplicados na cultura da soja sobre o milheto cultivado em sucessão

-1 ), diclosulam (0,035 kg ha-1), sulfentrazone (0,600 kg ha-1) e flumioxazin (0,050 kg ha-1) e uma testemunha, aplicados logo apos a semeadura do cultivar de soja Msoy-6101. Nas subparcelas, realizou-se a semeadura do milheto, cultivar ADR-7010, em quatro periodos, correspondendo a 0, 40, 80 e 120 dias apos a aplicacao dos herbicidas (DAA). Durante a conducao do ensaio, foram determinados os niveis de intoxicacao, estande, altura e massa seca da parte aerea das plantas de milheto. No final do ciclo foi avaliado o rendimento de graos da cultura. O hibrido de milheto ADR-7010 apresentou elevada sensibilidade com relacao a atividade residual dos herbicidas sulfentrazone, diclosulam e imazaquin quando cultivado logo apos a aplicacao destes. A bioatividade dos herbicidas imazaquin, diclosulam e flumioxazin nao foi suficiente para alterar o rendimento de graos do milheto cultivado em sucessao a soja (120 DAA), mostrando que esse intervalo de tempo e suficiente para dissipacao desses herbicidas. Dos herbicidas pre-emergentes avaliados, o sulfentrazone apresentou maior atividade residual, influenciado negativamente o rendimento da cultura durante o intervalo de tempo estudado. Palavras-chave: carryover, sulfentrazone, diclosulam, imazaquin, flumioxazin, Pennisetum glaucum. ABSTRACT - The objective of this study was to evaluate the persistence of herbicides applied in pre-emergence in soybean crop and the effects of these herbicides on pearl millet grown in succession. The herbicides imazaquin (0.160 kg ha-1), diclosulam (0.035 kg ha-1), sulfentrazone (0.600 kg ha-1), and fumioxazin (0.050 kg ha-1) were used immediately after sowing of soybean Msoy-6101, in plots of 80 m2, divided into sub-plots of 20 m2 (5 x 4 m). A randomized block design with four replications was used in a split-plot scheme 5 x 4. In the sub-plots, pearl millet hybrid ADR-7010 was sown in four periods after herbicide application, corresponding to 0, 40, 80 and 120 days after herbicide application (DAA). Pear millet injury, stand, height and dry biomass of the plant were evaluated at 7, 15, and 28 days after emergence; crop grain yield was evaluated at the end of the cycle. Pearl millet hybrid ADR-7010 showed high sensitivity to the residual activity of sulfentrazone, imazaquin, and diclosulam when grown immediately after herbicide application. The bioactivity of imazaquin, diclosulam, and flumioxazin was not sufficient to affect grain yield of millet grown after soybean (120 DAA), suggesting that this interval is sufficiently long for dissipation of these herbicides. Among the pre-emergent herbicides, sulfentrazone showed longer residual activity, negatively influencing the crops yield during the time interval studied.

Seletividade de clomazone isolado ou em mistura para a cultura do algodoeiro

Clomazone is one of the most important herbicides applied in pre-emergence in cotton, even though not much is known about its selectivity to this crop. This work was carried out to evaluate the selectivity of clomazone applied alone or in tank mixtures with other herbicides applied in pre-emergence in cotton. The experiment was designed as a randomized block, with four replicates, using two-fold checks. Thirteen treatments were evaluated, constituted by different combinations of clomazone with S-metolachlor, diuron, prometryne, alachlor, oxyfluorfen, and trifluralin. After herbicide application, visual crop injury was evaluated, as well as stand, plant height, number of bolls per plant and cotton+seed yield. Clomazone alone applied at 1.00 and 1.25 kg ha-1 or associated to S-metolachlor (0.76 kg ha-1), diuron (1.50 kg ha-1), prometryne (1.50 kg ha-1), alachlor (1.44 kg ha-1), and trifluralin (1.80 kg ha-1) was selective to cotton cv. Nu-Opal. However, its association with oxyfluorfen (1.25 + 0.19 kg ha-1), with trifluralin + diuron (1.25 + 1.80 + 1.50 kg ha-1), and with trifluralin + prometryne (1.25 + 1.80 + 1.50 kg ha-1) resulted in reduced cotton yield.

Influência do estádio de desenvolvimento de Cenchrus echinatus na supressão imposta por atrazine

Cenchrus echinatus is an important weed in areas cultivated with corn, sorghum and pearl millet in Brazil. Although atrazine is one of the most used herbicides in such crops, not much has been done to determine weed susceptibility as a function of its growth stage at post-emergence applications. This work aimed to evaluate the suppression imposed by the herbicide atrazine applied at post-emergence, during three developmental stages of this weed. The assay was carried out under greenhouse conditions, in pots of 10 dm-3, in a factorial scheme 5 x 3 composed by five rates of atrazine (0; 0.5; 1.5; 2.5 and 4.0 kg ha-1 ), combined with three stages of C. echinatus development during herbicide spraying at post-emergence (first pair of leaves; second pair of leaves and two tillers). Applications performed at later stages of weed development were inefficient to provide control, despite significant reductions of dry biomass, plant height and production of reproductive structures. Aiming at weed control, the best results were found for rates ³ 3.5 kg ha-1 in plants at the stage of first pair of leaves.

Supressão imposta pelo mesotrione a Brachiaria brizantha em sistema de integração lavoura-pecuária

Mesotrione is an important herbicide applied to corn, but little is known about the susceptibility of species, such as Brachiaria brizantha to this herbicide. The objective of this study was to evaluate the suppression imposed by mesotrione in Brachiaria brizantha, intercropped with maize. The trial was conducted in a randomized block design with four replications, corresponding to seven doses of mesotrione (0; 12; 24; 48; 96; 144 and 192 g ha-1), a control (corn without interference) and a treatment with beard grass grown as a single. Both crops were sown on the same day. The herbicide was applied at 20 days after emergence of the species. Mesotrione showed the greatest potential for plant toxicity in B. brizantha plants, when applied at a dose of 192 g ha-1. However, grass forage showed satisfactory tolerance to the herbicide, indicating potential use in crop-livestock systems. The inter-specific competition led to reductions in corn yield, and the best dose-response relationship to benefit both cultures was obtained by using 96 g ha-1 of mesotrione.

Residual activity of herbicides used in soybean agriculture on grain sorghum crop succession

The sorghum is a kind of prominence before the cultures used in succession in the Brazil. However, little information concerning the effects of residual activity of herbicides on the crop in this region are known. The objective of this study was to evaluate the residual activity of herbicides used in weed management in soybeans as well as check their effects on grain sorghum grown in succession. For the field experiment, we used a randomized block design with four replications. Eight herbicide treatments were evaluated: imazaquin (0,161 kg ha-1), diclosulam (0,035 kg ha-1), sulfentrazone (0,600 kg ha-1) and flumioxazin (0,05 kg ha-1) in applications made before emergency and chlorimuron-ethyl (0,015 kg ha-1), imazethapyr (0,060 kg ha-1), imazethapyr (0,100 kg ha-1) and fomesafen (0,250 kg ha-1) applied post-emergence soybean (V3 stadium, 18 DAE), and a control without herbicide application. The grain sorghum (cv. AG-1040) was sown after the harvest of soybeans. The residual activity of these herbicides was determined by bioassay, using the same sorghum cultivars evaluated in the field during the period from 0 to 200days after application the treatments. The sorghum crop showed high sensitivity to residual activity of the herbicide sulfentrazone, diclosulam and imazethapyr dose of 0,100 kg ha-1, even when grown after soybean harvest. Furthermore, the residual activity of sulfentrazone exceeded the range of assessment of bioassay, and more than 200 days.

Tolerance of grain sorghum to 2,4-D applied in post-emergence.

Grain sorghum is one of the major species cultivated as a winter crop in savannah areas in Brazil. Although 2,4-D is currently used on this crop, little has been done to understand crop susceptibility as a function of its vegetative stage at spraying. The present work was carried out to determine the selectivity of 2,4-D applied in post-emergence on grain sorghum. The cultivar AG-1040 was grown in 10 dm-3 pots under greenhouse conditions. The experiment was set up in a completely randomized design, in a factorial scheme 5 x 3, composed by five rates of 2,4-D (0, 210; 420; 840 and 1.608 g ha-1), applied at three phenological stages: three, five and nine completely expanded leaves. Visual crop injuries were more intense when the herbicide was applied at the earlier stages of sorghum development. However, the main negative effects related to plant productivity and lodging were observed in herbicide applications carried out at later stages of crop development.

Controle de plantas daninhas na cultura do milho por meio de herbicidas aplicados em pré-emergência

This study aimed to estimate the effectiveness of weed control in maize ( Zea mays L.), under a no-till system, in the Cerrado (Brazilian Savanna) region, by applying pre-emergence herbicides. Two experiments were carried out in Montevidiu, Goias State, Brazil, during the 2007/2008 crop, in a randomized block design, with four replications. The following treatments were evaluated: atrazine (1,600 g ha -1 ), atrazine + s-metolachor (1,665 g ha -1 + 1,305 g ha -1 ), s-metolachor (1,680 g ha -1 ), atrazine + simazine (250 g ha -1 + 250 g ha -1 ), and control with and without weeds. It was found out that, 28 days after the treatments application, the herbicides atrazine and s-metolachor were not effective in controlling Cenchrus echinatus and Alternanthera tenella , respectively. The associations between atrazine + s-metolachor and atrazine + simazine have provided significant increases in the Euphorbia heterophilla and Alternanthera tenella control. The presence of weeds had a negative effect on crop yield. KEY-WORDS: Zea mays ; atrazine; s-metolachor; simazine; no-tillage.

Selectivity of the herbicide tembotrione to pearl millet

The present study was carried out to evaluate the selectivity of the herbicide tembotrione, applied at post-emergence of pearl millet. Two experiments were conducted, evaluating primarily the effect of the herbicide on three pearl millet cultivars (ADR-300, ADR-500 and ADR-7010) under greenhouse conditions. The hybrid ADR-7010 was later tested under field conditions, when increasing doses of tembotrione were applied at two stages of plant development (four and seven fully developed leaves). Under greenhouse conditions, the cultivars presented similar percentages of reduction of shoot dry matter accumulation, after tembotrione application at 75.5 g ha-1 at the four-expanded leaf stage .Under field conditions, tembotrione showed the highest phytotoxicity when applied at the early stages of hybrid ADR-7010. Tembotrione selectivity is dependent on the dose and developmental stage of pearl millet at the time of herbicide application. The use of tembotrione over growing millet in areas intended for grain production was found to be a viable alternative to weed control.

Tolerância do cultivar de milheto ADR-300 ao herbicida atrazine

The aim of this study was evaluate the selectivity of the herbicide atrazine to the culture of pearl millet (Pennisetum glaucum). The test was implemented in units of 10 dm -3 o f soil under conditions of a greenhouse in a completely randomized design in factorial scheme 5 x 3 with four replicates, corresponding to five dose of atrazine: 0; 0.5; 1.5; 2.5 and (4.0 kg i.a. ha -1 ), applied in three stages of growth of pearl millet (two, four and eight expanded leave), cultivar ADR-300. We evaluated the levels of phytotoxicity at 7; 14 and 21 days after application, plant height, dry mass and mass of spike. The major symptoms of phytotoxicity, reducing the number of tillers and dry biomass were obtained from applications made in the early stages of culture and intensified with increasing dose of atrazine. With respect to the mass of spike, doses below 1.5 kg ha -1 of atrazine showed greater flexibility in the application stage and can be used