Irrigation and fungicide application on disease occurrence and yield of early and late sown sunflower

Abstract

A B S T R A C TThe objective of this study was to evaluate the effect of irrigation and fungicide application on the occurrence of diseases and cypsela yield of two genotypes of sunflower. The experiments were carried out in Santa Maria-RS, during the regular season in 2007 and the late season, in 2008. Plants were sown on 04/09/2007 and 21/01/2008, in a completely randomized design, with four replicates. A 2 x 6 factorial scheme was used, with the sunflower genotypes Aguará 03 and Hélio 358 and six fungicide application schemes, which were determined by the FAST forecasting system, as follows: FAST 16, FAST 22 and FAST 28, without irrigation, FAST 16 IRR under irrigated condition, in addition to irrigated control (CONTROL IRR) and control (CONTROL). Disease progress was analyzed based on weekly observations of the severity of the symptoms. It was verified that irrigation increases sunflower cypsela yield in the regular season, provided that weather conditions are not favorable for the occurrence of alternaria and septoria leaf blights or that fungicides are applied. In the late season, under irrigated condition, fungicide application is necessary to control alternaria and septoria leaf blights.Irrigação e aplicação de fungicidas na ocorrência de doenças e na produtividade do girassol em períodos de safra e safrinha R E S U M O Objetivou-se, neste trabalho, avaliar o efeito da irrigação e da aplicação de fungicidas na ocorrência de doenças e na produtividade de cipselas de dois genótipos de girassol. Os experimentos foram conduzidos em Santa Maria, RS, nos períodos de safra de 2007 e safrinha de 2008. As semeaduras foram realizadas em 04/09/2007 e 21/01/2008, sendo utilizado o delineamento inteiramente casualizado, com quatro repetições. Foi utilizado um esquema fatorial 2 x 6, constituído pelos genótipos de girassol Aguará 03 e Hélio 358 e seis esquemas de aplicação de fungicida, determinados em função do sistema de previsão FAST, os quais foram: FAST 16, FAST 22 e FAST 28, sem irrigação, FAST 16 IRR, em condição irrigada, além das testemunhas irrigada (TEST IRR) e não irrigada (TEST). O progresso da doença foi analisado com base nas observações semanais da severidade dos sintomas da doença. Verificou-se que a irrigação aumenta a produtividade de cipselas de girassol no cultivo de safra desde que as condições meteorológicas não sejam favoráveis para a ocorrência de mancha de alternaria e septoria ou que se apliquem fungicidas. Na safrinha em condição irrigada, a aplicação de fungicidas é necessária para o controle de mancha de alternaria e septória.

The Effects of Potassium Fertilization and Irrigation on the Yield and Health Status of Jerusalem Artichoke (Helianthus tuberosus L.)

“…In the cited study, relative humidity was higher in the early (72-97%) than late rainy season, which increased the area under the disease-progress curve (AUDPC) and the disease severity index (DSI). Maldaner et al [60] examined the effect of irrigation and fungicides on the prevalence of infections and yields in two sunflower genotypes. They found that irrigation increased sunflower yields, but only in periods when weather conditions hindered the development of diseases caused by Alternaria spp.…”

Severity of Septoria Leaf Spot and Sunflower Yield Due to Leaf Wetness Duration

“…The variable that influenced the increase in severity was the additional artificial leaf wetness duration immediately after the pathogen distribution on the plants in the area as the air temperature and rainfall conditions were the same for all treatments. Sentelhas et al (1996), Loose et al (2012) and Maldaner et al (2015) also found a correlation between leaf wetness and the alternaria leaf blight, with increased disease severity in greater leaf wetness condition. Furthermore, Leite and Amorim (2002a) observed an increase in the lesion severity and density of alternaria leaf blight in sunflower with increased leaf wetness duration in a controlled environment.…”

“…Rainfall is one of the factors that most act on pathogen dispersion, enabling the beginning of a new cycle in a larger area and accelerating disease spreading (Agrios, 2004). Sentelhas et al (1996), Loose et al (2012) and Maldaner et al (2015) also verified that the condition of greater rainfall favors the septoria leaf spot in sunflower. Thus, we also observed an accelerated growth of the septoria leaf spot in a greater rainfall condition (Figure 1), which conditioned the increase in the observed disease severity.…”

Irrigation can create new green bridges that promote rapid intercontinental spread of the wheat stem rust pathogen

“…Menzies 1967, Rotem and Palti 1969, Dixon et al 2015, De Villiers et al 2017, Avila et al 2019, Swett 2020) through increased canopy moisture, changes in stomatal conductance, and microcracking, although in some instances reduced water stress may also enhance disease resilience (Swett 2020). Potential mitigation strategies include more targeted fungicide use and the extensive use of durable rust-resistant varieties and drip irrigation systems in regions where irrigation is to take place (Sanogo 2004, Daugovish et al 2012, Maldaner et al 2015, Swett 2020. Given the importance of irrigation as an adaptation strategy for climate change and improved food security, it is recommended that irrigation expansion plans be accompanied by risk assessment analyses to identify any associated mitigations also required.…”