Soybean Rust Severity Research Articles

Machine learning in the classification of asian rust severity in soybean using hyperspectral sensor

Traditional monitoring of asian soybean rust severity is a time- and labor-intensive task, as it requires visual assessments by skilled professionals in the field. Thus, the use of remote sensing and machine learning (ML) techniques in data processing has emerged as an approach that can increase efficiency in disease monitoring, enabling faster, more accurate and time- and labor-saving evaluations. The aims of the study were: (i) to identify the spectral signature of different levels of Asian soybean rust severity; (ii) to identify the most accurate machine learning algorithm for classifying disease severity levels; (iii) which spectral input provides the highest classification accuracy for the algorithms; (iv) to determine a sample size of leaves that guarantees the best accuracy for the algorithms. A field experiment was carried out in the 2022/2023 harvest in a randomized block design with a 6x3 factorial scheme (ML algorithms x severity levels) and four replications. Disease severity levels assessed were: healthy leaves, 25 % severity, and 50 % severity. Leaf hyperspectral analysis was carried out over a wide range from 350 to 2500 nm. From this analysis, 28 spectral bands were extracted, seeking to distinguish the spectral signature for each severity level with the least input dataset. Data was subjected to machine learning analysis using Artificial Neural Network (ANN), REPTree (DT) and J48 decision trees, Random Forest (RF), and Support Vector Machine (SVM) algorithms, as well as a traditional classification method (Logistic Regression - LR). Two different input datasets were tested for each algorithm: the full spectrum (ALL) provided by the sensor and the 28 spectral bands (SB). Tests with different sample sizes were also conducted to investigate the algorithms' ability to detect severity levels with a reduced sample size. Our findings indicate differences between the spectral curves for the severity levels assessed, which makes it possible to differentiate between healthy plants with low and high severity using hyperspectral sensing. SVM was the most accurate algorithm for classifying severity levels by using all the spectral information as input. This algorithm also provided high classification accuracy when using smaller leaf samples. This study reveals that hyperspectral sensing and the use of ML algorithms provide an accurate classification of different levels of Asian rust severity, and can be powerful tools for a more efficient disease monitoring process.

Reduction of the severity of Asian soybean rust with foliar application of silicon dioxide

Asian soybean rust (Phakopsora pachyrhizi; ASR) is one of the main diseases that affect soybeans, and it is controlled mainly with chemical fungicides. Induction of plant defense with silicon dioxide (SiO2) application could also be considered to control the disease. However, there is no information on the use of SiO2 as a source of silicon to control ASR. Silicon is an element related to the induction of plant defense mechanisms. Thus, the aim of this study was to verify the in vitro effect of SiO2 on the germination of uredospores of P. pachyrhizi and whether foliar application reduces ASR severity. The in vitro experiment was conducted with six treatments (0; 0.1; 1; 10; 100; 1000 μg.L−1 of SiO2) while the in vivo experiment was carried out with four treatments (0; 1; 2.5; 5% SiO2) under controlled conditions. There was no effect of SiO2 on the germination of uredospores of P. pachyrhizi, yet there was a reduction of up to 85% in the number of uredia with application of 4% SiO2. Plants that received 5% of SiO2 accumulated about 60% more silicon in their leaf tissues compared to the control treatment, increasing 22.99 mg kg−1 of silicon for each percentage point of SiO2 applied. Thus, our study demonstrates that foliar application of SiO2 reduces the severity of ASR and provides greater accumulation of silicon in soybean leaf tissues.

A Little Helper: Beneficial Bacteria with Growth-Promoting Mechanisms Can Reduce Asian Soybean Rust Severity in a Cell-Free Formulation

Growth-promoting bacteria are already used in sustainable agricultural systems in Brazil. The market is dominated by inoculants and biological pesticides, which do not reach the full potential of this tool in the agricultural sector. This study aimed to evaluate four bacterial strains for the presence of growth promotion mechanisms, as well as the reduction of Asian rust severity in soybean plants and its effects on three antioxidant enzymes during pathogenesis. The plants were treated using the bacterial cells and/or their biosurfactants before inoculation of the pathogen (IOP). Severity was measured based on a diagrammatic scale at 14, 18 and 21 days after IOP, and the activities of the enzymes SOD, CAT, and APX were evaluated 21 days after IOP. Treatments containing only bacterial cells were not efficient in reducing the severity, with losses of leaf area reaching 15%, while the addition of biosurfactants led to a result that is similar to the biofungicide, based on Bacillus subtilis (Serenade®). The presence of direct growth promotion mechanisms can be observed in all isolates, as well as the role of bacterial metabolites, especially lipopeptides, in the biological control of diseases and the modulation of the plant’s immune response.

Spray nozzles and curtain of chains in fungicide application to control Asian soybean rust

The proper choice of spray nozzles and spray boom configuration is of paramount importance for fungicidal effectiveness, promoting better foliar coverage, especially in the lower canopy of the crop. In this sense, the present study evaluates the influence of fungicides applied with different spray nozzles, with and without curtain of chains, on Asian rust control and on the yield of soybean cultivar BMX Ativa RR. The experimental design was a randomized block, with four spray nozzles (Albuz ® ATR 1.0; Albuz ® ATR 0.5; Magnojet ® ADT 11002; and Magnojet ® CH100) and two spray boom configurations (with curtain of chains; and without curtain of chains). The experiment had four replicates and a control without fungicide application. The variables under study were the severity and control of Asian soybean rust, thousand grain weight, and soybean yield. The results indicate that using the curtain of chains in fungicide applications is a technically viable alternative to increase soybean yield. When used along with empty conical jet and triple flat jet nozzles, this technology is highly efficient in controlling Asian soybean rust.

Asian Rust Severity in Soybean Sown in December and February in Mato Grosso State

The objective of this work was to assess the effect of December sowing time with February on the Asian soybean rust severity. In on-farm trials two soybean treatments sowing in December (2020) (DSS.) and February (2021) (FSS) were assessed for Asian soybean rust severity in 24 sites, in three regions of Mato Grosso state. The DSS treatment was established in the growers commercial farms and the FSS in a 5 ha area sown specifically for this treatment. The DSS treatment was conducted in 16 sites and the FSS in eigth. For rust control fungicides with efficacy higher than 60% were sprayed consisting of DMIs, QoIs and SDHIs in double or triple mixtures, always added by multisites (chlorothalonil, mancozeb, or copper oxychloride). About eighty soybean leaflets from four plots repetitiond, demarcated at random in each field, were taken in each smpling. In laboratory leaflet severity was appraised and area under disease progress curve (AUDPC) calculated. Related to DSS, the AUDPC overall mean was 174 units and receiving 6.9 fungicide spraying and for FSS 26 units with 4.8 fungicide sprayings. Our results reinforce that the sowing time can be changed from the end of December to February to maintain soybean crop sustainability.

Secondary Metabolites of Pseudomonas aeruginosa LV Strain Decrease Asian Soybean Rust Severity in Experimentally Infected Plants.

Asian Soybean Rust (ASR), a disease caused by Phakopsora pachyrhizi, causing yield losses up to 90%. The control is based on the fungicides which may generate resistant fungi. The activation of the plant defense system, should help on ASR control. In this study, secondary metabolites of Pseudomonas aeruginosa LV strain were applied on spore germination and the expression of defense genes in infected soybean plants. The F4A fraction and the pure metabolites were used. In vitro, 10 µg mL−1 of F4A reduced spore germination by 54%, while 100 µg mL−1 completely inhibited. Overexpression of phenylalanine ammonia lyase (PAL), O-methyltransferase (OMT) and pathogenesis related protein-2 (PR-2; glucanases) defense-related genes were detected 24 and 72 h after soybean sprouts were sprayed with an organocopper antimicrobial compound (OAC). Under greenhouse conditions, the best control was observed in plants treated with 60 µg mL−1 of PCA, which reduced ASR severity and lesion frequency by 75% and 43%, respectively. Plants sprayed with 2 and 20 µg mL−1 of F4A also decreased severity (41%) and lesion frequency (32%). The significant reduction in spore germination ASR in plant suggested that the strain of these metabolites are effective against P. pachyrhizi, and they can be used for ASR control.

Alternative products on the control of asian rust soybean

In recent years, it has been observed a significant expansion of the organic market. In this context, the main phytosanitary problem of soybean in the organic system is Asian rust (Phakopsora pachyrhizi), for which it is difficult to control, considering the restriction of products authorized for use in the organic system and the limitation of research related to this management system. The objective of this study was to evaluate the effect of alternative products on the germination of uredospores, on the severity of soybean rust on detached leaves and the control of the disease under greenhouse and field conditions. The alternative treatments were calcium silicate, lime sulphur, bordeaux mixture, and copper oxychloride. The variables analyzed were uredospores germination, disease severity, defoliation level, area under the disease progress curve (AUDPC), a thousand grain mass and productivity. The results obtained indicate that there is a possibility of using copper oxychloride to manage the Asian rust in organic production systems. Copper oxychloride had reduced the germination of uredospores and when evaluated under controlled conditions using detached leaves and greenhouse, it had reduced the severity of the disease. In field conditions, copper oxychloride at the doses of 588 and 882 g ha-1 reduced severity and AUDPC, in addition to increasing productivity at 1434 kg ha-1 in relation to the control. It is concluded that copper oxychloride can be used as a tool in the management of Asian rust in organic systems of soy production.

Asian Soybean Rust Severity Sowed in Different Seasons

In on-farm trials, the foliolar severity of Asian soybean rust was evaluated in 44 areas, in three regions of Mato Grosso sown in December (2019) and February (2020). Several susceptible cultivars were used in different crop systems; insect pests and weeds were controlled with different management systems by the farmers. Forty soybean leaflets from four plots replications, demarcated at random in each field were taken. In laboratory foliolar severity was appraised. For rust control in the trials conducted in February, fungicides with efficiency greater than 60% were used consisting of DMIs, QoIs and SDHIs in double or triple mixtures, always adding multisites (chlorothalonil, mancozeb, copper oxychloride). The severity was greater in the fields sown in December (4.84% than in February 0.68%). The number of fungicides spraying/ha in December was 6.4 and February 4.6. It is discussed that through the use of multisites fungicides, the mutation potential in Phakopsora pachyrhizi is reduced and that the spores from areas cultivated in February, probably due to unfavorable environment, do not survive during the soybean free-period. Our results indicate that the sowing period can be changed from the end of December to February, since multisites fungicides are always used.

English

Asian soybean rust, if not well managed, can reduce grain yield up to 90%. Due to the severe damage caused by the disease, especially in Brazil, it is important to evaluate management strategies combined with fungicides, to minimize the losses. The aim of the work was to evaluate the effect of adopting different combined management strategies on the severity of soybean rust and its impact on the performance of the crop. Research was carried out at 2016/2017 and 2017/2018 growing seasons. Soybean cultivar NA 5909 RG® (susceptible to Asian rust), LG 60163 IPRO® (highly tolerant) and TMG 7062 IPRO® INOX® (resistant) were evaluated with different combinations of fungicide, copper and potassium phosphites foliar fertilizers applications, in two development stages, R1 (early flowering) and R5.1 (early grain filling). Disease severity assessments were performed at R1 and repeated every 14 days (up to R5 + 14 days) to determine the area under the Disease Progress Curve (AUDPC). The genetics of resistance to Asian soybean rust contributed to the less progress of the disease in plants. Even with differential responses between cultivars and treatments applied to the severity of Asian soybean rust, the disease did not compromise grain yield in both growing seasons. Key words: Phakopsora pachyrhizi, fungicide, foliar fertilizers, genetic resistance.

Comparative Severity Analysis of Asian Soybean Rust in Soybean Farms Sown in December and February in Mato Grosso, 2018/19 Growing Season

The objective of this work was to compare the leaflet severity of Asian soybean rust in farms sown in December and February in the state of Mato Grosso. In the survey, 28 fields were sampled in 14 counties in the North, West and South regions of the state. A total of 40 leaflets were collected per plot, in randomized treatments with four replication and three crop phenological stages. Leaflet severity was assessed according to a diagrammatic scale. The data were expressed as leaflet severity, submitted to linear regression analysis, calculated the area under the disease progress curve (AUDPC) considering the three phenological stages sampled, and the means compared by the Tukey’s test. Leaflet severity was significantly higher in the fields sown in December than in February, as well the number of fungicides sprayings. Our results indicate that the proposed change in seeding time from December to February can be implemented by significantly reducing risks and in compliance with the principles of IN 002/2015.

Alternative products on Asian soybean rust control and their influence on defoliation, productivity and yield components

ABSTRACT To study the efficiency of Asian soybean rust (Phakopsora pachyrhizi) control and to test the effects of using alternative products and fungicides, two field experiments were conducted during the harvest seasons 2013/2014 and 2014/2015. Treatments for the experiments were: 1- control (water); 2- acibenzolar-S-methyl; 3- calcium; 4- micronutrients: copper, manganese and zinc; 5- micronutrients: manganese, zinc and molybdenum; 6- NK fertilizer; 7- Ascophyllum nodosum, and 8- azoxystrobin + cyproconazole. The evaluated variables were: Asian soybean rust severity, defoliation, productivity and yield components. Based on severity data, the area under the disease progress curve was calculated. In the two experiments, the alternative products had no effect on Asian soybean rust or defoliation. Only the treatment with fungicide controlled the disease and decreased defoliation. The yield component affected by the treatments was the number of pods per plant, in both harvest seasons. Treatment with the fungicide protected soybean from yield loss in both experiments. Defoliation was strongly correlated with the weight of one thousand seeds and the number of pods per plant, emphasizing the importance of maintaining the leaf area to ensure the maintenance of the yield components in soybean crop.

Agronomic and Economic Evaluation of Sequential Spray of Silicon and Fungicides for a Sustainable Soybean Crop

This study was carried out to determine whether the yield of soybean cultivars and the severity of Asian Soybean Rust (ASR) are influenced by foliar spray of silicon exclusively or along with a fungicide mixture, as well as the economic viability of their use for a sustainable crop. The experiment was performed in randomized-block design, five replicates, two soybean cultivars and (2×6) + 2 factorial arrangements: S1 (AlSi at R1 + R4); S2 (AlSi at R1 + R5.1); S3 (AlSi at R1 + FM at R4); S4 (FM at R1 + AlSi at R4); S5 (AlSi at R1 + FM at R5.1); S6 (FM at R1 + AlSi at R5.1); NC and PC (negative and positive control). The economic evaluation and sensitivity analysis were undertaken for Anta 82 RR. There was no interaction effect between the factors, and cultivar CD 2737 had a higher yield. ASR was less severe in CD 2737, and S3 and S5 provided the lowest disease severity. Exclusive spray of aluminum silicate was able to reduce the number of lesions with uredinia, open uredinia and uredinia per lesion. S3 increased grain yield, resulting in higher revenues and a 66.1% gross margin. Sensitivity analysis revealed that S3 was profitable in all scenarios.

Use of isolated fungicides for the control of Phakopsora pachyrhizi in soybean

The occurrence of diseases in soybean crop has negatively affected its development and caused significant losses in productivity. Among the diseases, Asian rust caused by the fungus Phakopsora pachyrhizi Sydow stands out because of its high severity. As a way of controlling, chemical fungicides is a tool used to mitigate the damage. The objective of this work was to evaluate the efficiency of different isolated fungicides in the control of Asian rust. The experiment was carried out in the experimental area of ​​the University of Cruz Alta in the state of Rio Grande do Sul with a randomized block design and four replications. The cultivar used was BMX Ativa, and the fungicide applications occurred before the interline closure and later with 15 days of interval between applications. The fungicides tested in the experiment were: metominostrobin + tebuconazole, piraclostrobin + fluxpyroxade, picoxystrobin + cyproconazole, Azoxystrobin + benzovindiflupir, picoxystrobin + benzovindiflupir, Trifloxystrobin + protioconazole, Pyraclostrobin + epoxiconazole + fluxpyroxade, Bixafen + protioconazole + Trifloxystrobin, Mancozebe + picoxystrobin + tebuconazole and control. The variables analyzed were yield kg ha-1, weight of one thousand seeds and disease severity. The fungicides Mancozebe + picoxystrobin + tebuconazole and bixafen + protioconazole + trifloxystrobin showed the highest yield, one thousand grain weight and lower severity of Asian soybean rust.

A new standard area diagram set for assessment of severity of soybean rust improves accuracy of estimates and optimizes resource use

AbstractSoybean rust (SBR), caused by Phakopsora pachyrhizi, is the most important yield‐damaging fungal disease of soybean due to severe reduction in healthy leaf area and acceleration of leaf fall. In experimental research, SBR severity is estimated visually aided/trained by a standard area diagram (SAD) developed and validated during the mid‐2000s (Old SAD). In this study, we propose a new SAD set for SBR with six true‐colour diagrams following linear increments (c. 15% increments) amended with four additional diagrams at low (<10%) severities, totalling 10 diagrams (0.2%, 1%, 3%, 5%, 10%, 25%, 40%, 55%, 70%, and 84%). For evaluation, 37 raters were split into two groups. Each assessed severity in a 50‐image sample (0.25%–84%), first unaided and then using either the Old SAD or the New SAD. Accuracy, precision, and reliability of estimates improved significantly relative to unaided estimates only when aided by the New SAD (accuracy >0.95). Low precision (<0.78) and a trend of underestimation with an increase in severity were the main issues with the Old SAD, which did not differ from unaided estimates. Simulation to evaluate the impact of the errors by different methods on hypothesis tests, showed that the new SAD was more powerful for detecting the smallest difference in mean control (e.g., 70% vs. 65% disease reduction) than the Old SAD; the latter required a 2‐fold increase in sample size to achieve the same power. There is a need to improve some SADs, taking advantage of new knowledge and technology to increase accuracy of the estimates, and to optimize both resource use efficiency and management decisions.

Relationship between soybean plant defoliation and Asian soybean rust severity

ABSTRACT Data from experiments conducted in the field with eight fungicide mixtures added of five mancozeb levels were used to generate gradients of soybean rust severity, plant defoliation, and soybean grain yield. The data were subjected to correlation analysis between defoliation and severity, defoliation and grain yield, and grain yield and rust severity. All correlations were significant, evidencing a relationship between variables. Analyses conducted in other studies have shown that severity control has greater influence on decision-making, compared to defoliation. Therefore, as defoliation is dependent on severity, evaluation of rust intensity is sufficient, suggesting that defoliation can be excluded from evaluation for this pathosystem.

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

Potassium (K) is one of the essential nutrients for plants and is involved in many cellular processes which might influence the severity of diseases. There are few reports of the effect of increasing concentrations of K in the field on the severity of the Asian soybean rust (ASR) caused by Phakopsora pachyrhizi. In this context, the objective of this work was to verify the influence of increasing concentrations of K on ASR, in the absence and presence of chemical control, in conditions that highly favored the development of the disease. Two experiments were conducted under field conditions and two also in the field but in pots with a capacity of 100 L. Evaluated concentrations of K were 0.0, 100, 200, and 400 mg/dm³, respectively in a randomized complete block design. The application of the fungicide mixture azoxystrobin (200 g/L) + cyproconazol (80 g/L) was performed at 45, 60, and 75 days after emergence. The severity of the disease, area under the disease progress curve (AUDPC), rate of disease progression (r), soybean productivity, and contents of chlorophyll a, b and total were evaluated. The severity, AUDPC, and r decreased with the increase of the concentration of K and fungicide application, while the rate of disease control and soybean productivity increased. Contents of chlorophyll a, b and total also had higher values according to the increase in the concentration of K. Potassium fertilization reduced the severity of ASR and grain yield under high disease pressure with or without chemical control.

Performance of new flat fan nozzle design in spray deposition, penetration and control of soybean rust

Fungicide application technology to control soybean rust (SBR) is lacking and requires optimization to improve spray coverage in the lower part of the crop canopy as well as the spray distribution uniformity. The goal of this study was to evaluate the effects of flat fan nozzles with different angles and spray volumes on the optimization of fungicide application in soybean, as well as on SBR and its effect on crop yield. For this purpose, a 2-year (2016–2018) field experiment was conducted in Botucatu, SP, Brazil. Three spray nozzles were evaluated: flat fan, double flat fan and angled flat fan, with two spray volumes. A quantitative analysis of the spray deposition was conducted, assessing the spray deposits on the lower and upper part of the plants with Brilliant Blue tracer. Furthermore, SBR severity was evaluated based on the number of pustules cm−2 and on the AUDPC, as well as the establishment of treatment control efficacy and its effect on soybean yield. Irrespective of the spray nozzles and volumes, the penetration of the droplets into the crop canopy was impaired at the reproductive stage, with less deposition in the lower part of the plant, although the larger spray volume provided greater spray deposition. All the treatments promoted effective control of the disease, with no changes in efficacy due to a larger spray volume or angled nozzles. The correct spray volume, especially with respect to the different growth stages, greatly influences spray deposition and penetration.

Evaluation of the efficacy and application timing of different fungicides for management of soybean foliar diseases in northwestern Argentina

Diseases are among the main factors that reduce soybean yields in Tucumán and other provinces in northwestern Argentina. The main diseases that affect the foliage of soybean plants in this region are target spot (caused by Corynespora cassiicola), Cercospora leaf blight (Cercospora kikuchii), and Asian soybean rust (Phakopsora pachyrhizi). The objective of this work was to evaluate the efficacy and application timing of different chemical fungicides for the management of these diseases in northwestern Argentina. Field trials were conducted during three growing seasons (2014/2015, 2015/2016, and 2016/2017). The fungicide treatments that presented statistical differences (P < 0.05) for target spot control compared to the untreated control in all growing seasons were those that included pyraclostrobin + epoxiconazole + fluxapyroxad (applied at R3, R5 and R3 + R5) and pyraclostrobin + epoxiconazole and azoxystrobin + cyproconazole at R3. For Cercospora leaf blight control, all treatments differed statistically from the untreated control in the 2014/2015 crop season, except for azoxystrobin + cyproconazole and azoxystrobin + benzovindiflupyr applied at R3 and pyraclostrobin + epoxiconazole at R5. Only azoxystrobin + cyproconazole at R3 in 2015/2016 and all the fungicide treatments in 2016/2017 differed statistically from the untreated controls. Soybean rust severity at R6 was low, 1.0% and 3.0% in the untreated control during 2014/2015 and 2015/2016, respectively, but increased to 54.2% in 2016/2017. Treatments that showed the lowest soybean rust severity values in the latter season were pyraclostrobin + epoxiconazole + fluxapyroxad (R3 + R5 and R5, with 17.4 and 17.1%, respectively), and azoxystrobin + benzovindiflupyr (R3 and R5, with 20.2 and 15.0%, respectively). Overall in this season, the efficacy of each fungicide for ASR control was better when applied at R5 than at R3. The treatments pyraclostrobin + epoxiconazole + fluxapyroxad applied at R3, R5 and R3+ R5 and treatments azoxystrobin + benzovindiflupyr and pyraclostrobin + epoxiconazole at R5 yielded significantly higher than the untreated control during all three seasons. These results should help improve management of soybean foliar diseases in northwestern Argentina.

Use of Copper-Based Pesticides to Control Fungal Diseases of Soybean in Northern Brazil

At level word fungal diseases that affect soybean crop are one of the main causes of low productivity and annual losses may reach 21% of total production. In this context, the objective of the study was to evaluate the efficiency of copper-based protectors associated with fungicides to control soybean diseases such as: asian soybean rust (Phakopsora pachyrhizi), target spot of soybean (Corynespora cassiicola) and cercospora leaf blight (Cercospora kikuchii) + frogeye leaf spot (Cercospora sojina) + brown spot (Septoria glycines), which together were considered as late-crop cycle diseases, with impact on grain yield, in the region of Aparecida do Rio Negro – TO, Brazil. Treatments were composed of different rates of copper-based pesticides associated with fungicides like Azimut® (first application), Orkestra® (second application), Ativum® (third application) and Horos® (fourth application) in soybean. Diseases were identified and crop damage evaluations on leaves were performed using LI-COR® portable meter 7 days after the fourth application. At physiological maturity, grain yield was evaluated. Combined rates of fungicides + Unizeb Gold® (1.5 kg ha-1), Difere® (0.5 L ha-1), and NHT® Copper Super at a rate higher than 0.109 L ha-1, were effective to control late crop-cycle diseases in soybean. Associated applications of fungicides + 0.219 L/ha of NHT® Copper Super reduced the severity of Asian soybean rust, target spot of soybean and late crop-cycle diseases with a greater increase in grain yield (4.5 Mg ha-1).

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

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&amp;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&amp;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.