How to manage diseases in soybean crops

How the correct positioning of fungicides and adequate control of diseases in soybean crops can result in protecting the productive potential of crops and the profitability of producers.

In the 2020/21 harvest, 21 trials were carried out across the main soybean producing regions of Brazil and Paraguay, conducted by research institutions, universities and consultants, called the “Expert Team Tour” group. At each location, two trials were carried out, one for the control of leaf spots and DFCs and the other for the control of Asian soybean rust.

The treatments were composed of combinations of widely recommended fungicides, applied at different times and management combinations. The evaluated treatments are described in Table 2.

The trials included 12 treatments and were conducted in a randomized block design with four replications (Table 3). Applications were carried out using a backpack sprayer with constant pressure (CO2) and a spray volume of 150L/ha.

The timing of the trials in each region favored the occurrence of certain diseases. Trials conducted in the South and Cerrado with sowing at the beginning of the recommended season showed the presence of leaf spots, mainly target spot, caused by Corynespora cassiicola, and DFCs such as septoria and cercosporiosis. Trials conducted in other locations in the Cerrado showed a predominance of target spots and in other locations in the South, DFCs predominated. In general, trials conducted at the end of the recommended sowing season were used to study the control of Asian rust, making a total of 11 trials with the presence of this disease. Data obtained in all trials were summarized through meta-analysis.

Asian rust

The trials with the occurrence of Asian rust and suitable for analysis totaled ten, five in the Cerrado and five in the South. In general, the trials did not show symptoms or signs of disease before the first application. In the southern region of Brazil, the first cases of Asian rust were reported in the first and second week of December 2020, in Paraná and Rio Grande do Sul, respectively. As in the 2019/20 harvest, the number of occurrences and the progress of the disease in the field were lower when compared to previous harvests. The same was observed in the Central-West/Cerrado. An exception to this was the southern region of Mato Grosso, notably in the municipalities of Campo Verde and Primavera do Leste, which showed an early onset of the disease.

In this scenario, all treatments with fungicide applications showed higher productivity than the control without application. Asian rust control, between treatments, ranged from 72,9% to 80,1% (Figure 1), with all treatments being significantly superior to the control, but with no significant difference between them (Figure 1). The trend towards better disease control was always observed when multisite fungicide was added to the programs (Figure 1). This difference in control with the use of multisite resulted in a significant difference in productivity when comparing program 6 with program 7 (Figure 2). Average productivity maintenance estimates (or productivity gains) ranged from 588kg/ha to 884kg/ha depending on the control program adopted. Among them, numerically, program with applications of Viovan (picoxystrobin + prothioconazole 25-30 DAE), Vessarya (picoxystrobin + benzovindiflupyr 40-45 DAE), Viovan + Controller NT (picoxystrobin + prothioconazole + mancozeb (55-60 DAE) and Aproach Power + Controller NT (picoxytrobin + cyproconazole) + mancozeb) presented the highest average productivity estimates in relation to the control (Figure 1).

The comparison between other treatments was organized according to the moment of application of picoxystrobin + prothioconazole in programs with one and two applications, reinforcement of programs with mancozeb protector, and different combinations of active ingredients. Among the programs with an application of picoxystrobin + prothioconazole, there was no significant effect between the moment of application of Viovan (first, second or third), both in the disease control and productivity parameters (Figure 2). The result shows that picoxystrobin + prothioconazole can be used in the first three applications without presenting a reduction in productivity performance.

In programs with two applications of picoxystrobin + prothioconazole there was also no effect between the timing of the applications (together and interspersed) (Figure 2). In the same programs, the results showed an average productivity gain of 139kg/ha with the reinforcement of Controller NT (mancozeb) in the program with two applications of picoxystrobin + prothioconazole. In the control of Asian rust, the productivity gain results demonstrated that the fungicide picoxystrobin + prothioconazole maintained its response, regardless of the moment of application.

Among the mixtures picoxystrobin + prothioconazole and trifloxystrobin + prothioconazole, programs with Viovan applications showed an average productivity of 182kg/ha higher than the treatment with trifloxystrobin + prothioconazole. There was no significant effect on productivity between the program with trifloxystrobin + prothioconazole + mancozeb vs Viovan (Figure 3). The program with Viovan + Controller NT (picoxystrobin + prothioconazole + mancozeb) showed a productivity of 214kg/ha higher than trifloxystrobin + prothioconazole without reinforcement with mancozeb. In the comparison of the two programs with reinforcement of Controller NT (mancozeb), Viovan (picoxystrobin + prothioconazole) showed a higher productivity of 112kg/ha.

Target spot

There were five trials conducted that showed the occurrence of target stain and met the criteria for meta-analysis. Target spot control ranged between 59,5% and 69,9% between treatments (Figure 1). The best target spot management program numerically was program 7 (Viovan + Vessarya + (Viovan + Controller NT) + (Aproach Power + Controller NT), with two applications of Viovan, one with multisite fungicide reinforcement and one application of Vessarya (picoxystrobin + benzovindiflupyr). In general, the best controls were observed where the program included two applications of prothioconazole (Figure 4). All treatments with fungicide applications showed higher productivity than the control without application. T5 programs with application of Viovan at 25-30 and 40-45 DAE +  Vessarya at 55-60 DAE + (Aproach Power + Controller NT) at 70-75 DAE and the T9 program, Vessarya + Viovan + (Viovan + Controller NT) + (Aproach Power + Controller NT) (T9) presented the highest estimates of productivity gain in relation to the control, with 673kg/ha and 656kg/ha, respectively. Treatment with azoxystrobin + benzovindiflupyr and trifloxystrobin + prothioconazole (T10) presented the smallest increase in productivity in relation to the control, with 456kg/ha (Figure 4).

When comparing programs with applications of picoxystrobin + prothioconazole, there was no significant effect between the introduction of Viovan in the first, second and third applications (Figure 5). In programs with two applications, the results suggest that for target spot control, the first and second applications of picoxystrobin + prothioconazole (T8) showed higher productivity than picoxystrobin + prothioconazole applied in the second and third applications (T5). In the Viovan programs tested, there was no effect on productivity from the mancozeb booster.

Between treatments with picoxystrobin + prothioconazole and trifloxystrobin + prothioconazole, there was no significant effect on target spot control and productivity between programs at the 5% significance level (Figure 6). When considering a 10% error level, programs with Viovan showed higher productivity than trifloxystrobin + prothioconazole.

Reinforcing the program with Controller NT (mancozeb) showed gains in productivity and corroborates with Godoy et al. (2020), who observed improvement in target spot control with the addition of multisite fungicides in network trials.

Cercosporiosis and DFCs

In the 2020/21 harvest, the trials conducted showed a significant occurrence of diseases known as DFCs. In total, two trials were used for analysis, and control of DFCs varied from 66,4% and 81,6% between treatments (Figure 7). All treatments with fungicide applications showed higher productivity than the control without application (Figure 7). Thus, as for target spot, program 7 with the first application of Viovan (picoxystrobin + prothioconazole); the second from Vessarya (picoxystrobin + benzovindiflupyr); the third application with Viovan + Controller NT (picoxystrobin + prothioconazole) + (mancozeb) and the fourth application of Aproach Power + Controller NT (picoxystrobin + cyproconazole) + (mancozeb) numerically showed the best control of DFCs.

 There was no significant difference in the control of DFCs when comparing the selected programs (Figure 8). However, the use of the multisite fungicide resulted in a 13% increase in the control of DFCs, when comparing programs 3 and 4 (Figure 8). The treatment with the application of Vessarya (picoxystrobin + benzovindiflupyr) in the first, Viovan in the second and Viovan + Controller NT in the third, closing with Aproach Power + Controller NT in the last application (Treatment 9) showed the highest estimated productivity gain (559kg/ha ) in relation to the witness (Figure 7).

When comparing programs with Viovan applications, there was no significant difference in the control of DFCs in relation to the moment of application of the fungicide: first, second or third (Figure 8). However, for a management with four applications, two applications of picoxystrobin + prothioconazole showed better numerical control than one application (Figures 7 and 8).

Regarding productivity, Viovan applications in the first and second (T5) showed productivity 21kg/ha higher than when applied in the second and third applications (T8) (Figure 8). Among the treatments with Viovan at the same time of application evaluated, the reinforcement of Controller NT (mancozeb) showed a significant increase in productivity of 135kg/ha when comparing program 8 with 9 (Figure 8).

Among the mixtures of picoxystrobin + prothioconazole and trifloxystrobin + prothioconazole, programs with applications of trifloxystrobin + prothioconazole showed an average productivity of 82kg/ha higher than the treatment with picoxystrobin + prothioconazole.

 There was no significant effect on productivity between the program with trifloxystrobin + prothioconazole + mancozeb vs picoxystrobin + prothioconazole (Figure 9). The program with Viovan + Controller NT (picoxystrobin + prothioconazole + mancozeb) showed a productivity of 52kg/ha higher than trifloxystrobin + prothioconazole without reinforcement of Controller NT (mancozeb). When comparing the two programs with Controller NT (mancozeb) reinforcement, Viovan showed a higher productivity of 94kg/ha.

Conclusions

In the control of Asian soybean rust, programs with the addition of multisite fungicides mancozeb to site-specific fungicides showed a higher average productivity of 139kg/ha. Viovan (picoxystrobin + prothioconazole) showed an increase/maintenance of productivity when inserted in the first, second and third application and a productivity of 182kg/ha higher than the program with trifloxystrobin + prothioconazole.

Picoxystrobin + prothioconazole presents target spot control efficiency, an increase in productivity of 559kg/ha in relation to the control, and for DFCs, the increase in productivity was 512kg/ha. 

The results confirm Viovan's broad spectrum of control, which combined with reinforcement with Controller NT (mancozeb) showed an increase/maintenance of soybean productivity.

Alfredo Riciere Dias¹,
Beno Kuzniewski¹,
Carlos Forcelini¹,
Carlos André Schipanski¹,
Carolina Deuner¹,
Caroline Wesp Guterres¹,
Eder Novaes Moreira¹,
Fabiano Victor Siqueri¹,
Ivan Pedro Araújo Jr¹,
Fabrício Packer²,
Guilherme Almeida Ohl¹,
Guilherme de Camargo Hüller²,
Hercules Diniz Campos¹,
José Fernando Jurca Grigolli¹,
José Nunes Júnior¹,
Luana Maria de Rossi Belufi¹,
Lucas Henrique Fantin¹,
Lucas Navarini¹,
Luis Henrique Kasuya¹,
Marcelo Giovanetti Canteri¹,
Marcelo Gripa Madalosso¹,
Marcio Goussain¹,
Mônica Anghinoni Müller¹,
Mônica Cagnin Martins¹,
Mônica Paula Debortoli¹,
Nédio Rodrigo Tormen¹,
Paulo Asunção¹,
Pedro Vuolo Maia Floresta²,
Rogério Rubin²,
Senio José Napoli Prestes¹,
Silvânia Helena Furlan¹,
Solange Maria Bonaldo¹,
Wilfrido Morel¹ and
Marcus Fiorini²,
¹Expert Team
²CortevaAgriscience