Deposição de gotas no dossel e controle químico de Phakopsora pachyrhizi na soja

Abstract

R ESU M OA deposição de gotas no dossel da cultura da soja com três pontas de pulverização e programas de controle químico da ferrugem asiática foram avaliados em experimento conduzido em campo, no município de Itaara, RS. Os tratamentos foram arranjados no delineamento de blocos ao acaso com quatro repetições, em esquema fatorial 2 x 3 x 3, representados por duas cultivares de soja, três pontas de pulverização e três programas de controle da ferrugem asiática. Os fungicidas foram aplicados nos estádios R1 e R4 da cultura. As variáveis analisadas foram: densidade de gotas, diâmetro mediano volumétrico (DMV), índice de área foliar (IAF), severidade da ferrugem asiática e rendimento de grãos da cultura. Elaborou-se, com base nos dados de severidade da ferrugem asiática, a área abaixo da curva de progresso da ferrugem (AACPF). As pontas de pulverização estudadas diferiram significativamente quanto à deposição de gotas nos três terços do dossel vegetal, DMV, AACPF e rendimento de grãos. O incremento médio no rendimento de grãos pela aplicação de fungicidas foi de 53,17% na cultivar Asgrow 8000 RG e 29,89% na cultivar Agiara RR. O IAF das cultivares influenciou na penetração e deposição de gotas no dossel da cultura. Palavras-chave: Glycine max, ferrugem asiática, pontas de pulverização Drop deposition on canopy and chemical control of Phakopsora pachyrhizi in soybeansA B ST R A C T Drop deposition on soybean canopy with three spray nozzles and chemical control programs of asian soybean rust were evaluated in two soybean cultivars, in a study carried out in Itaara, RS. The treatments were arranged under completely randomized block design with four replications, in a factorial design 2 x 3 x 3, utilizing two soybean cultivars, three spray nozzles and three chemical control programs. The fungicide applications were accomplished in R1 and R4 growth stages. Drop density, volumetric medium diameter (VMD), leaf area index (LAI), disease severity and grain yield were the variables measured. Based on the severity data of asian rust the area under disease progress curve (AUDPC) was calculated. The spray nozzles studied were significantly different in relation to drop deposition on soybean canopy, VMD, AUDPC and grain yield. The soybean grain yield was increased by 53.17% on Asgrow 8000 RG and 29.89% on Agiara RR cultivar, as a result of fungicide application. The LAI of cultivars influenced drop deposition and penetration into canopy.

Spray droplet spectrum and spray deposition in different soybean sowing systems

“…It must be observed that plant architecture has a direct influence on the efficiency of the application technology of agrochemicals. Tormen et al (2012) verified that soybean cultivars with higher LAI and more lateral ramifications close the canopy faster and make the penetration of the water droplets into the bottom of the plant difficult. Ozkan et al (2007) also verified that with a LAI of 6.4 most droplets are retained in the upper canopy, facilitating the proliferation of diseases in the lower canopies, which are chemically unprotected and have a favorable microclimate.…”

“…According to Tormen et al (2012), the leaves of the plant top intercept a considerable part of the sprayed droplets, preventing the lower leaves from receiving significant amounts of active ingredient in the plant health control. Therefore, the plant lower part is highly dependent on the plant architecture, as well as leaf area and LAI.…”

Chemical Control of Asian Soybean Rust as a Function of Cultivar, Row Spacing and Spray Bar Support Systems

“…When analyzing the effect of the air supply through a series of works, Oliveira et al (2016) indicated that this mechanism of support to the spray bar had no effect on the performance of agrochemicals and the control levels of phytopathogenic fungi. The contrasting and variable effects on the Vortex ® system may be associated with the different canopy opening levels, which can be influenced by the plant arrangement (Holtz et al, 2014), depending on the characteristic of the cultivar Tormen et al, 2012), as well as by the time of the day of spraying, due to the variation of the horizontal angle of soybean leaves throughout the day (Graziano et al, 2017;Moura et al, 2017). Moreover, the spray tip angle, droplet size and speed, adjuvants and mixture volume are factors that also influence droplets' penetration along the canopy of the plant (Cunha et al, 2014, Madureira et al, 2015Prado et al, 2015;Cunha et al, 2016;Weber et al, 2017, França et al, 2018.…”

Spray Nozzles Performance in Fungicides Applications for Asian Soybean Rust Control

“…In the application of systemic fungicide, the pulverized spray solution must remain in contact with the leaf for a minimum period, so that the plant can absorb the active ingredient, according to Yu et al (2009). In this sense, the active ingredient needs to be placed in the target under the risk of not controlling the disease (Tormen et al, 2012). Therefore, it is possible to emphasize that the spray nozzles that contributed to the lower AUDPC of the soybean rust and for greater safety in the application in relation to the other spray nozzles used were the Hypro GUARDIAN 120015 single pre-orifice flat spray, showing medium drop characteristics.…”