Controle em pré semeadura da cultura de soja de algodão voluntário tolerante ao glyphosate e amônio glufosinate e de Eleusine indica

The objective of the research was to determine the efficacy of pre-emergence-applied herbicides sprayed at different rates and times before soybean planting under water deficit conditions, to control volunteer cotton plants tolerant to glyphosate and ammonium glufosinate and Eleusine indica. The trial was conducted on Formosa do Rio Preto/BA, during the 2015/16 growing season, in a randomized complete block design, with four replications and ten treatments, which included: glyphosate + diclosulam 960 + 25,2 g ha-1 a.i., glyphosate + diclosulam 960 + 35 g ha-1 a.i. sprayed 50, 20 and 0 days before soybean planting (DBP), glyphosate + flumioxazin 960 + 50 g ha-1 a.i., glyphosate + sulfentrazone 960 + 150 g ha-1 a.i., glyphosate + sulfentrazone 960 + 200 g ha-1 a.i. sprayed 0 DBP and an untreated treatment. Assessments of percentage visual control were performed 7 and 0 DBP and 14 and 45 days after soybean planting (DAP) and soybean grain yield was measured. Diclosulam at 25,2 and 35 g ha-1 a.i. controlled volunteer cotton plants when sprayed 50, 20 and 0 DBP. Sulfentrazone sprayed 0 DBP at 150 and 200 g ha-1 a.i. controlled volunteer cotton while flumioxazin did not provide adequate control. Diclosulam at 25,2 to 35 g ha-1 a.i. was the best treatment to control Eleusine indica when sprayed 0 DBP. Soybean yield was considered equal between treatments.O objetivo do trabalho foi avaliar a eficácia de herbicidas aplicados em pré-emergência, em diferentes doses e épocas, antes da semeadura de soja sob condição de déficit hídrico, para o controle de plantas voluntárias de algodão, tolerante aos herbicidas glyphosate e amônio glufosinate, e Eleusine indica. O ensaio foi conduzido no município de Formosa do Rio Preto/BA, durante a safra 2015/16, utilizando o delineamento experimental de blocos ao acaso, com quatro repetições e dez tratamentos, sendo: glyphosate + diclosulam (960 + 25,2 g ha-1 e.a./i.a.) e glyphosate + diclosulam (960 + 35 g ha-1 e.a./i.a.), aplicados aos 50, 20 e 0 dias antes da semeadura (DAS), glyphosate + flumioxazin (960 + 50 g ha-1 e.a./i.a.), glyphosate + sulfentrazone (960 + 150 g ha-1 e.a./i.a.) e glyphosate + sulfentrazone (960 + 200 g ha-1 e.a./i.a.) aplicados 0 DAS, além de um tratamento controle. Avaliações visuais de controle foram efetuadas aos 7 e 0 DAS, aos 14 e 45 dias depois da semeadura (DDS) e a produtividade da soja estimada. A aplicação do herbicida diclosulam é eficaz no controle de algodão voluntário, quando aplicado 50, 20 e 0 DAS, nas doses de 25,2 e 35 g ha-1 i.a. O tratamento sulfentrazone é eficaz, quando aplicado 0 DAS nas doses de 150 e 200 g ha-1 i.a., enquanto o herbicida flumioxazin não é eficaz. No controle de Eleusine indica o diclosulam foi o melhor tratamento quando aplicado 0 DAS a 25,2 e 35 g ha-1 i.a. A produtividade foi considerada igual entre tratamentos

Efficacy, absorption and translocation of glyphosate and 2,4-D in Spermacoce verticillata (L.)

No cerrado brasileiro as associações entre glifosato e 2,4-D são comuns. Neste contexto, a planta daninha Spermacoce verticillata (L.) (vassourinha-de-botão) apresenta tolerância ao herbicida 2,4-D e suscetibilidade ao glifosato (sendo essa condicionada ao estádio fenológico da planta daninha). O objetivo deste trabalho foi determinar e quantificar a absorção e translocação de 14C glifosato e 14C 2,4-D na associação de diferentes doses dos dois herbicidas sobre plantas de S. verticillata, verificar a eficácia de controle de diferentes doses dos herbicidas glifosato e 2,4-D e o acúmulo de ácido chiquímico nos tecidos da parte aérea das plantas nos tratamentos de glifosato e 2,4-D isolados e associados. Para tal, foram realizados 4 experimentos em casa de vegetação e laboratório. Os dois primeiros experimentos com moléculas radiomarcadas utilizando dois fatores herbicidas 14C glifosato (0; 720 e 1440 g e.a ha-1) e 14C 2,4-D (0; 167,5; 335 e 670 g e.a ha-1) sendo apenas glifosato ou 2,4-D radiomarcado adotado em cada experimento, ambos no esquema fatorial 2 x 4 e 3 x 3 respectivamente, a análise das plantas foi efetuada às 72 horas após aplicação (HAA). Para o experimento de eficácia de controle, foi utilizado o esquema fatorial 6 x 6 sendo os fatores glifosato (0; 180; 360; 720; 1440 e 2880 g e.a ha-1) e 2,4-D (0; 83,75; 167,5; 335; 670 e 1340 g e.a ha-1) isolados e associados avaliados aos 7, 14 e 21 dias após aplicação (DAA). Para o experimento de quantificação do acúmulo de ácido chiquímico os fatores glifosato (0; 720 g e.a ha-1) e 2,4-D (0; 670 g e.a ha-1) foram aplicados isolados e associados em esquema fatorial 2 x 2. Em todos os ensaios o delineamento experimental adotado foi o de blocos casualizados, as unidades experimentais contaram com plantas com 2-3 pares de ramos laterais. Os dados foram submetidos a análise de variância a 95% de significância e quando significativos o teste de Tukey ou Scott-Knott foi adotado. A absorção e translocação de 14C glifosato na dose de 720 g e.a ha-1 foi reduzida quando associada as doses do 2,4-D, enquanto para o glifosato na dose de 1440 g e.a ha-1 não foram detectadas diferenças estatísticas. A absorção e translocação do 14C 2,4-D aumentaram significativamente na presença do glifosato. A eficácia de controle aos 21 DAA demonstra que o glifosato entre 720 e 2880 g e.a ha-1 foi efetivo (>90%), porém o 2,4-D não (65%), a dose de 720 g e.a ha-1 apresentou redução significativa de controle quando associada ao 2,4-D, enquanto as doses de 1440 e 2880 g e.a ha-1 não foram influenciadas. A concentração de ácido chiquímico no tratamento de glifosato a 720 g e.a ha-1 associado ao 2,4-D a 670 g e.a ha-1 foi de 9.1 µg, enquanto no tratamento de glifosato isolado de 40.1 µg. Portanto, dependendo das doses utilizadas na associação verificou-se impacto na absorção e translocação dos herbicidas glifosato e 2,4-D, que pode refletir em diminuição na concentração de ácido chiquímico e controle de S. verticillata, tornando o controle dependente da dose associada.In Brazilian cerrado associations between glyphosate and 2,4-D are often performed. On this context the weed Spermacoce verticillata (L.) (shrubby false button weed) presents tolerance to the herbicide 2,4-D and susceptibility to glyphosate (being conditioned to the development stage of the weed). The objectives of the present work were, determine and quantify the absorption and translocation of 14C glyphosate and 14C 2,4-D in the association of different doses from both herbicides on S. verticillata plants, verify the efficacy of control of different doses from herbicides glyphosate and 2,4-D and the shikimic acid accumulation in plant tissues from aerial part of S. verticillata plants on treatments of glyphosate and 2,4-D isolated or associated. A total of four experiments were held on green house and laboratory. The first two experiments with radiolabeled molecules were conducted using the herbicide factors 14C glyphosate (0; 720 and 1440 g a.e ha-1) and 14C 2,4-D (0; 167,5; 335 and 670 g a.e ha-1) being only glyphosate or 2,4-D radiolabeled adopted in each experiment, both in factorial scheme 2 x 4 and 3 x 3 respectively, the plant analysis performed at 72 hours after application (HAA). For the efficacy of control trial, the factorial scheme 6 x 6 was used being the factors glyphosate (0; 180; 360; 720; 1440 and 2880 g a.e ha-1) and 2,4-D (0; 83,75; 167,5; 335; 670 and 1340 g a.e ha-1) alone and associated evaluated at 7, 14 and 21 days after application (DAA). For the shikimic acid accumulation experiment the factors glyphosate (0; 720 g a.e ha-1) and 2,4-D (0; 670 g a.e ha-1) were applied alone and associated in factorial scheme 2 x 2. In all experiments the randomized complete block design was adopted and the experimental units composed by plants with 2 3 side branches. The data were submitted to analysis of variance at 95% significance level and when significant Tukey or Scott-Knott test was adopted. The absorption and translocation of 14C glyphosate at 720 g a.e ha-1 were reduced when associated with 2,4-D, while for glyphosate at 1440 g a.e ha-1 no differences were observed. The absorption and translocation of 14C 2,4-D enhanced significantly when glyphosate was associated. The efficacy of control at 21 DAA resulted in efficient control (>90%) for glyphosate from 720 to 2880 g a.e ha-1, however for 2,4-D was not efficient (65%), the glyphosate dose of 720 g a.e ha-1 presented significant efficacy reduction when associated to 2,4-D, while doses of 1440 and 2880 g a.e ha-1 were not influenced. The shikimic acid concentration within glyphosate treatment at 720 g a.e ha-1 when associated to 2,4-D at 670 g a.e ha-1 was 9.1 µg, while in treatment of glyphosate alone was 40.1 µg. According to adopted doses at the association impact was confirmed in absorption and translocation of herbicides glyphosate and 2,4-D, which might reflect in reduction in shikimic acid concentration and S. verticillata control, making control dependent of the associated dose

Effects of cowpea mild mottle virus on soybean cultivars in Brazil

Soybean stem necrosis is caused by cowpea mild mottle virus (CPMMV), transmitted by the whitefly Bemisia tabaci. CPMMV has already been recorded in all major soybean-producing areas of Brazil. The impacts caused by CPMMV to the current Brazilian soybean production are unknown, thus the main objective of this study was to evaluate the effects of CPMMV infection on the main important soybean cultivars grown in the Southern and Midwestern regions of Brazil. Although asymptomatic in some of the tested cultivars, CPMMV infection significantly reduced the plant height, the number of pods per plant and the 1,000-grain weight. In addition, estimated yield losses ranged from 174 to 638 kg ha−1, depending on the cultivar. Evidence of seed transmission of CPMMV was observed in the BMX POTÊNCIA RR cultivar. These results suggest that CPMMV could have an important role in the reduction of soybean productivity in Brazil, but symptomless infections might be hiding the actual impact of this pathogen in commercial fields and infected seeds could be the primary inoculum source of the virus in the field