Effect of the interaction between fungicide application time and rainfall simulation interval on Asian Soybean Rust control effectiveness

Abstract

Environmental factors affect the performance of fungicides in soybean (Glycine max (L.) Merr.). They also influence the residual activity of the products applied to the leaves. The objective of this study was to assess the control effectiveness of the interaction between fungicide application and rainfall simulation on Asian Soybean Rust (ASR). Two experiments were conducted, one in the greenhouse, in a completely randomized design, and the other in the field, in a randomized block design. Both the experiments had the same factorial arrangement of 6x5, with four replications. Factor A: Five fungicide applications time at 0400 h, 0900 h, 1400 h, 1800 h, 2300 h and, a control with no application; Factor B: four intervals of time between the application of fungicide and rainfall simulation at 0, 30, 60 and 120 min for the experiment in the greenhouse and at 2, 30, 60, 120 min for the experiment in the field. A control was included for both the experiments with no rainfall. The number of days to the appearance of the first pustules was determined, along with severity of ASR, relative chlorophyll index and productivity. It was found that the ASR control effectiveness of fungicide applications in soybean plants in sunlight was less efficient with rainfall simulation. The rainfall simulation had greater negative effect on disease control effectiveness in applications conducted at night under dew conditions. The application conducted at 0900 h showed the greatest disease control effectiveness in both greenhouse and in the field conditions. The 1400 h application showed decreased fungicide control residual and ASR control effectiveness, possibly due to a combination of the low relative humidity and high temperature. Rainfall simulation carried out at 120 min after application still had the ability to affect the ASR control effectiveness. Key words: Chemical control. Dew. Glycine max L. Night application. Phakopsora pachyrhizi. ResumoOs fatores ambientais afetam o comportamento dos fungicidas em soja (Glycine max (L.) Merr.). Eles também influenciam a atividade residual de produtos aplicados na folha. O objetivo do estudo

Factors influencing the performance of phosphites on the control of coffee leaf rust

“…In soybeans, the rainfall simulation, even 120 min after fungicide application, decreased the Asian soybean rust control effectiveness (Stefanello et al 2016). It is important to highlight that different factors may impact the effect of products employed in disease control, including plant genotype, product, adjuvant, leaf age, drop size and time of application (Stefanello et al 2016). The results indicate that Cu afforded a better tenacity to phosphite than K. Therefore, less removal of Cu phosphite deposits on coffee leaves should be expected due to rainfall under field conditions.…”

“…Despite the absence of literature dealing with the effect of washing on phosphite's performance, the efficiency of pesticides is known to be affected by leaf washing. In soybeans, the rainfall simulation, even 120 min after fungicide application, decreased the Asian soybean rust control effectiveness (Stefanello et al 2016). It is important to highlight that different factors may impact the effect of products employed in disease control, including plant genotype, product, adjuvant, leaf age, drop size and time of application (Stefanello et al 2016).…”

Soybean Rust Epidemics as Affected by Weather Conditions in Brazil

“…Several studies reported that rainfall itself is considered an epidemic triggering factor for SBR occurrence (Del Ponte et al, 2006;Megeto et al, 2014) since it enhances periods with free water over the plant surfaces. Once rainfall is strongly related to within-canopy spore dispersal, such a variable has a remarkable influence on the performance of fungicide sprays applied for SBR control (Stefanello et al, 2016).…”

“…Besides air temperature and LWD, rainfall can also affect SBR occurrence. Rainfall regime is considered to be an epidemic triggering factor of SBR, by creating a favorable environment for the pathogen (Del Ponte et al, 2006;Megeto et al, 2014) and unfavorable for fungicide spray application in order to control the SBR (Stefanello et al, 2016). Influence of rainfall on SBR progress was observed in Brazil, where areas with rainfall between 250 and 450 mm showed final disease severity over 70%; whereas areas with rainfall lower than 125 mm presented severity below 30% (Del Ponte et al, 2006).…”

Drying Time of Systemic and Protectant Fungicides on Coffee Leaves Exposed to Artificial Rain for the Control of Leaf Rust

“…Studies have shown that the adverse effect of rain is directly related to the interval between pesticide application and its occurrence (Stefanello et al, 2016). Debortoli (2008) showed that simulated rain affected the control of Asian soybean rust negatively, especially when no adjuvant was used mixed with the fungicide.…”