Phosphate Fertilization Reduces the Severity of Asian Soybean Rust Under High Disease Pressure

Ana Claudia R Mochko,Douglas F Parreira,Laércio Zambolim

doi:10.5539/jas.v11n1p261

Abstract

Mineral nutrition of plants is a strategy that can be used in the management of plant diseases. Therefore, the objective of this work is to determine which phosphorus dose reduces the severity of Asian soybean rust (Phakopsora pachyrhizi) with or without chemical control. Two trials were conducted under field conditions with six P doses (0, 25, 50, 100, 200 and 400 mg/dm&sup3;), and two trials in 100 L pots at P doses 0, 100, 200 and 400 mg/dm3. The inoculation of border rows and inoculation directly on plants in pots was performed with 105/mL of fungus urediniospores 15 days before the application of fungicide to increase the disease pressure. The application of fungicide (azoxystrobin + ciproconazole) was carried out at the R1 stage, and afterwards the mixture was reapplied three times in chemical control treatments. The results showed that the application of triazol + strobilurin fungicides in the presence of P decreased the severity of the disease (area under disease progress curve and disease infection rate) greater than in the absence of the fungicides. The productivity and levels of chlorophyll a, b and total also increased with chemical control in the presence of P. The dose 400 mg/dm3 of P was the most efficient in a soil with a low fertility, and 200 mg/dm&sup3; was efficient in a soil with a high fertility. In conclusion the application of the fungicides triazol + strobilurin was very important to get good control of Asian soybean rust; phosphate fertilization contributed to the amelioration of Asian soybean rust.

Highlights

Brazil stands out in the world scenario of soy production, being the second largest producer and exporter in the world
Four experiments were conducted to study the effect of phosphate fertilizer and or chemical control of Asian soybean rust being two in the field (FT1 and field test 2 (FT2)), and two inside plastic house (PT1 and pot test 2 (PT2))
For all treatments of the experiments conducted in the field (FT1 and FT2) and in pots (PT1 and PT2), there was no significant difference in the interaction between sprayed and non-sprayed treatments in pots

Summary

Introduction

Brazil stands out in the world scenario of soy production, being the second largest producer and exporter in the world. Production may be limited due to losses caused by diseases such as Asian soybean rust (ASR) caused by the fungus Phakopsora pachyrhizi H. In Brazil, ASR was reported for the first time in 2001 in the southern region of the country (Yorinori et al, 2005). The management of ASR is mainly performed by using fungicides from the chemical group of triazoles, strobilurins and carboxamides isolated or in mixture (Xavier et al, 2015). In addition to the chemical control, crop measures such as sanitary emptiness, planting of early varieties, anticipation of planting time (Twizeyimana et al, 2011), adjustment in plant density by area (Roese et al, 2012) and balanced fertilization are cultural measures extremely important in the management of this disease (Balardini et al, 2006)

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