Microsoft Word - 9-Agra_36931 1188 Original Article Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 CHEMICAL CONTROL OF FOLIAR DISEASES IN SOYBEAN DEPENDS ON CULTIVAR AND SOWING DATE O CONTROLE QUÍMICO DE DOENÇAS FOLIARES NA CULTURA DA SOJA DEPENDE DO CULTIVAR E DA ÉPOCA DE PLANTIO Rodrigo DE ALMEIDA1; Carlos Alberto FORCELINI1; Felipe Rafael GARCÉS-FIALLOS2 1 Agronomist Engineer, MSc Agronomy (Plant Pathology), University of Passo Fundo. Passo Fundo, RS, Brazil. 2 Agronomist Engineer, Specialist in Microbiology, MSc Plant Pathology, PhD Plant Pathology. Professor at Faculty of Agronomy and Veterinary Medicine, University of Passo Fundo. Passo Fundo, RS, Brazil. 3 Agronomist Engineer, MSc Agronomy (Plant Pathology), PhD Plant Genetic Resources. Professor at Faculty of Industrial Engineers, University of Guayaquil. Guayaquil, Ecuador. Email: felipe.garcesf@ug.edu.ec ABSTRACT: The aim was to study the effect of early application of two fungicide mixtures on the control of Asian rust and powdery mildew, as well as on grain yield in five soybean cultivars at two sowing dates. The experiment was carried in the experimental area of FAMV/UPF. The cultivars A 4910 RG (super-early), BMX Apolo RR, A 6001 RR and Fundacep 55 RR (early) and Coodetec 214 RR (moderate), established at 13/11/2007 and 3/12/2007 were used. Trifolia of these cultivars were treated twice with the fungicides ciproconazol + azoxystrobin (Priori Xtra®, 0.3 L ha-1 plus Nimbus® adjuvant 0.6 L ha- 1) and epoxiconazol + pyraclostrobin (Opera®, 0.5 L ha-1), in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. The severity (% of affected leaf area) of powdery mildew and number of lesions cm2 of Asian rust were evaluated. After that plants were harvested, the thousand grain weight (g) and grain yield (kg ha-1) were quantified. The experimental design was a split-plot with four replicates, where the main plot were the five cultivars, and the subplots were the control treatment (untreated plants) and the six chemical control programs. Tukey and t-Student tests (p≤0.05) were used for separation of means of treatments and seasons, respectively. In general terms, foliar application of fungicides controlled both Asian rust and powdery mildew, as well as generated an increase on the thousand grain weight and grain yield. However, there seems to be an interaction among soybean genotypes and sowing date. Thus, our results allow us to infer that the chemical control of leaf diseases in the soybean crop depends of the cultivar and sowing date. KEYWORDS: Glycine max L. Triazols. Strobilurins. Powdery mildew. Asian soybean rust. Grain yield. INTRODUCTION Diseases are the major problem in soybean crop, causing great damage and losses annually. In Southern Brazil, Asian rust (Phakopsora pachyrhizi Syd. & P. Syd.) and powdery mildew (Erysiphe diffusa (Cooke & Peck) U. Braun & S. Takam.) stand out. Asian rust intensity is directly influenced by the frequency of rainfall over the crop cycle (DEL PONTE et al., 2006). However, powdery mildew has been more intense in this region of the country in recent seasons due to low rainfall (DE ALMEIDA et al., 2014). In susceptible cultivars, both Asian Rust and powdery mildew may originate yield losses between 35 and 90%, respectively (HARTMAN et al., 1999). The current soybean cultivars are susceptible to these foliar diseases, but there are variations in intensity among genotypes, due to possibly the climatic conditions of each season. These predisposing conditions in the no-tillage crop environment are related to the sowing time, due to the temperature and wetting conditions of each period (DE ALMEIDA et al., 2014). The use of synthetic fungicides is the main tool used currently for the control foliar diseases, thus preserving the productive potential of soybean crop. However, some factors such as genotype choice, timing of application and season may affect the fungicides efficiency. For example, applications still in vegetative stages of crop and repeated up to three times, besides controlling the Asian rust, can generate an increase of plants leaf area, unlike of later applications (BOLLER et al., 2008; GARCÉS- FIALLOS; FORCELINI, 2011a; 2011b). For the control of powdery mildew in early cultivars with lower leaf area index, applications may be done before (BOLLER et al., 2008). On the other hand, the use of early-cycle cultivars and sowing at preferential times, but not late, may prevent a longer exposure time of trifolia to pathogen (REIS et al., 2006). However, the management of diseases such as Asian rust, as well as the choice of application time, is important in the maintenance of soybean leaves, Received: 15/12/16 Accepted: 05/05/17 1189 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 which finally reflect in a higher grain weight (GARCÉS-FIALLOS; FORCELINI; 2011b). Recommendations about fungicides spraying still in vegetative stage of soybean (pre-closure of space between the sowing lines), may reach the middle and lower third of plants, resulting in an adequate management of main diseases and increases in yield, stimulated the conduct of this experiment. Thus, the aim was to study the effect of early application of two fungicide mixtures on the control of Asian rust and powdery mildew, as well as on grain yield in five soybean cultivars at two sowing dates. MATERIAL AND METHODS The experiment was carried in the experimental area of Faculty of Agronomy and Veterinary Medicine, University of Passo Fundo, at 2007/08 crop season. Seed soybeans were sown in two seasons, the first at 13/11/2007 and the second at 03/12/2007. Genotypes and treatments Five cultivars of different cycles (DE ALMEIDA et al., 2014) were used, being three super- early (A 4910 RG), early (BMX Apolo RR, A 6001 RR and Fundacep 55 RR) and moderate (Coodetec 214 RR). The genotypes were chosen because they represent a large area of cultivation in State of Rio Grande do Sul. Trifolia of the five cultivars were treated twice with the fungicides ciproconazol + azoxystrobin (Priori Xtra®, 0.3 L ha-1 plus Nimbus® adjuvant 0.6 L ha-1) and epoxiconazol + pyraclostrobin (Opera®, 0.5 L ha-1), in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. The volume of broth used in all applications was 200 L ha-1, with spray tip TJ60 11002 (100), using a CO2 pressurized spray, calibrated at a pressure of 2 bar. Experimental conditions The area used in this experiment contained white oats as previous crop (crop established during the winter harvest). With a no-tillage seeder were sown 12 seeds per linear meter. These seeds were first treated with the insecticide imidacloprid + thiodicarb (Cropstar®, 0.3 L ha-1) and the fungicide carbendazin + thiram (Derosal Plus®, 0.2 L ha-1). The experimental units were had six rows of five m spaced by 0.45 m, totaling 11.25 m2 and 360 plants per experimental unit. The four rows central were considered the useful plot. Fertilization in the sowing line was arranged of 250 kg ha-1 of formula N-P2O5-K2O (0-20-30). Three applications of insecticides were carried during crop growth cycle. Other activities related to experiment management were carried out according to culture needs. Evaluation of powdery mildew and Asian rust The severity (% of affected leaf area) of powdery mildew and number of lesions cm2 of Asian rust were quantified in all central leaflets of five soybean plants harvested at random on the two outer lines of the experimental unit. A stereoscopic microscope (ZEISS model Stemi 2000-C) was used for the quantification of these diseases. The severity assessment powdery mildew was estimated at 01/13 and repeated at 01/23, 02/2, 12/02, 22/02, 03/03, 03/13 and 03/23. The integration of the cumulative scores resulted in the area under the disease progress curve (AUDPC), according to trapezoidal integration equation described in Campbell; Madden (1990). The number of lesions cm2 only was quantified at phenological stage R7.1 (beginning maturity and green leaflets). Quantification of thousand grain weight and grain yield Grain was harvested using a Wintersteiger combine harvester (Win-tersteiger AG, Ried/I, Austria), on the four central lines at phenological stage R9 (harvest maturity). Immediately after the harvest, the grains were separated from the impurity, standardized to 13% humidity and estimated the thousand grain weight (g) and grain yield (kg ha-1). Plots of Fundacep 55 RR and CD 214RR plants established in the second season were affected by hail rain at 21/04/2008. Experimental design and statistical analysis The experimental design was a split-plot with four replicates, where the main plot were the five cultivars, and the subplots were the control treatment (untreated plants) and the six chemical control programs. After verification of homogeneity of the variances (Bartlett's test) and normality of the residues (Shapiro-Wilks test), data were subjected to analysis of variance. When the assumptions were satisfied, the 1190 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 data were submitted to ANOVA. Tukey and t-Student tests (p≤0.05) were used for separation of means of treatments and sowing date, respectively. All the analysis was performed in the GraphPad® Prism 5 statistical software. RESULTS AND DISCUSSION Evaluation of powdery mildew and Asian rust Although Asian rust and powdery mildew were found and evaluated, the second disease affected the soybean cultivars more intensively over time. Perhaps the climatic conditions favored only powdery mildew. The average temperature and total rainfall among 01/01 and 04/04/2008 were 20.2 °C and 660.3 mm, respectively. Precipitation was below normal in January (Figure 1). Erysiphe diffusa the causal agent of powdery mildew, is favored by temperatures between 18 and 24 °C, and does not need leaf wetting, requiring only of between 50 and 90% relative air humidity (HARTMAN et al., 1999; GONÇALVES et al., 2009), conditions that were recorded in the experiment. A ve ra ge t em p er at u re ( °C ) R ai n fa ll ( m m ) Figure 1. Rainfall (columns, mm) and average daily temperature (line, °C) from 01/01/2008 to 04/30/2008 in Passo Fundo, RS. Source: www.cnpt.embrapa/agromet/ The mixtures of fungicides applied at the three times reduced the AACPD of powdery mildew in average 50%, in most cultivars in the two sowing date, when compared to control (Table 1). The exception was in cv. Fundacep 55 RR in the second season, where the average spraying of pyraclostrobin + epoxiconazol at pre-closure of space between rows and phenological stage R5.1 was similar to control. It is known that mixtures as strobirulins and triazols efficiently controls the powdery mildew (GODOY; CANTERI, 2004). On the other hand, the advantage of use of fungicides mixtures is that the possibility of selection of fungicide resistant strains of powdery mildew may be reduced, besides contributing to the control of other soybean diseases as Asian rust (BLUM et al., 2002). The AACPD of powdery mildew was different among the treatments with fungicide in some cultivars (Table 1). For instance, a higher control of powdery mildew was observed in leaflets of cv. BMX Apolo RR sprayed with azoxystrobin + ciproconazol in the second season. Although the two mixtures have similar chemical groups, there is the possibility that one of them has higher efficiency. In this regard, Garcés-Fiallos et al. (2011) comparing the efficiency of two fungicide mixtures to control leaf diseases in wheat crop, they found that pyraclostrobin + epoxiconazol together with spray nozzles that generate fine drops, besides controlling the diseases may generate an increase in grain yield. Another possibility is that the leaf area of some genotypes interfered in the fungicides spraying. 1191 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 Table 1. Area under the disease progress curve (AUDPC) of powdery mildew based on the severity (%) on leaflets of six genotypes established in two sowing date, treated twice with the fungicides ciproconazol + azoxystrobin and epoxiconazol + pyraclostrobin, in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. Passo Fundo, RS, Brasil. Harvest 2007-2008 Fungicide Stage GENOTYPES A 4910 RG BMX Apolo RR A 6001 RR Fundacep 55 RR Coodetec 214 RR I II I II I II I II I II Untreated plants 65.11a 96.57a 68.23a 125.39a 69.67a 115.01a 37.98a 71.17a 40.63a 121.81a Azoxystrobin + Ciproconazol PRE + 21 days 10.55b1 27.48c 14.75b 58.00c 28.76b 48.35b 5.23b 26.59c 13.19b 71,56c PRE + R5.1 15.57b 22.16c 21.31b 55.14c 37.05b 51.31b 11.33b 22.39c 22.68b 75,45c R1 + R5.1 22.59b 53.17b 20.85b 52.48c 24.01b 54.82b 8.00b 31.41 bc 15.14b 66,67c Pyraclostrobin + Epoxiconazol PRE + 21 days 24.70b 54.35b 26.87b 99.70b 32.78b 69.42b 10.68b 25.93c 10.97b 68,92c PRE + R5.1 31.39b 55.68b 23.90b 90.69b 33.06b 73.06b 14.49b 58.67ab 25.89b 100,25b R1 + R5.1 23.77b 61.94b 19.74b 86.57b 22.86b 74.09b 13.03b 32.06bc 22.41b 76,54c Means 26.98B 53.63A 27.50B 80.79A 35.20B 68.59A 13.86B 37.91A 21.81B 82.77A CV (%) 36.09 21.91 37.97 10.04 21.00 13.5 43.11 26.69 24.72 7.65 1 Means followed by lowercase and capital letters in the column and row, respectively, do not differ significantly by the Tukey test (p≤0.05). 1192 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 Fungicides generated a control of Asian rust in average 80%, when compared to control (Table 2). The efficiency of these mixtures to control this disease has been reported by several authors (GODOY; CANTERI, 2004; SCHERM et al., 2009). For instance, pyraclostrobin + epoxiconazol applied at phenological stage V9 (stem with nine leaf) besides controlling the disease (GARCÉS-FIALLOS; FORCELINI, 2011a; GARCÉS-FIALLOS; FORCELINI, 2013), may generate an increase in leaf area of soybean plants (GARCÉS-FIALLOS; FORCELINI, 2011b). However, the number of lesions cm-2 in control leaflets of some cultivars was similar to treated ones (BMX Apolo RR and Coodetec 214 RR in the two and the first season, respectively) or some application time (phenological stages R1 and R5.1) with pyraclostrobin + epoxiconazol (A 6001 RR). Perhaps, the low intensity of the disease in these cultivars and sowing date interfered in the results, generating even a high coefficient of variation. A higher intensity of Asian rust and powdery mildew was observed in the cultivars evaluated in the second sowing season, when compared to first (Tables 1 and 2), possibly due to inoculum source of plants established in the first season. Considering the availability of inoculum, the first crops may present lower disease intensity compared to the later ones. The inoculum availability is higher in areas sown at end of the recommended period (REIS et al., 2006). Leaf spraying made in the second season at pre-closure of space between rows + phenological stage R5.1 (cvs. Fundacep 55 RR and Coodetec in the two season) and at phenological stages R1 + R5.1 (cv. A 6001 RR) did not efficiently control powdery mildew and Asian rust, respectively. Perhaps, to powdery mildew the time interval was too long, whereas to Asian rust the fungicides application was late. Between the intensity of diseases and the cycle of cultivars, only was observed an increasing behavior of Asian rust. For instance, the number of lesions cm-2 in leaflets of cv. 4910 RG super-early was in average 20-fould higher than that of cv. CD 214 RR moderate-cycle (Table 2). The use of early- cycle plants may reduce the time of exposure to pathogen, as well as sowing at preferential seasons, avoiding late sowings. Early-cycle cultivars may have lower damage when compared to late-cycle ones (REIS et al., 2006). According to Forcelini (2009), two applications would be enough to protect the early and semi-early cultivars. However, our results showed that two applications were sufficient to control the disease. What must be taken into account is that in longer-cycle genotypes, there is a final period of one to two weeks in which plants may be damaged by increased disease intensity (FORCELINI, 2009). Quantification of thousand grain weight and grain yield The thousand grain weight was in average 10% higher in plants treated with fungicide, compared to those not treated (Table 3). Fungicides applications in soybean crops generate a higher number of grains, pods, grains per pods and grain weight per plant (SOARES et al., 2004; GARCÉS-FIALLOS; FORCELINI, 2011b). However, the mixtures and the application times differentially affected this productive variable in the evaluated genotypes. Although the fungicides applied in pre-closure of the space between the lines may induce an increase of grain yield, besides controlling diseases such as Asian rust (GARCÉS-FIALLOS; FORCELINI, 2013), this behavior seems to depend of genotype and season. For instance, the cvs. A 4910 RG and Fundacep 55 RR in the first and second sowing date, respectively, the thousand grain weight of one of the treatments was similar to control. Fungicides positively affected grain yield of cv. BMX Apolo RR and A 6001 RR in both sowing date, and of cvs. Coodetec 214 RR and A 4910 RG in the first and second sowing date, respectively, when compared to control (Table 4). Fungicides application in aerial part of soybean crop, besides reducing the Asian rust, may influence in a higher yield of grains (MILES; LEVY, 2007). The higher production obtained in these cultivars was possibly due to protection of healthy leaf area. This variable may influence the grain filling (GARCÉS-FIALLOS; FORCELINI, 2011b), reflecting itself at the end on grain yield. However, this productive variable was influenced by the moment of application, differently in each genotype and season. For example, in the first season the grain yield in cv. A 6001 RR treated with azoxystrobin + ciproconazol was lower than those treated with pyraclostrobin + epoxiconazol. Meanwhile, in the second season there was no difference between fungicides and grain yield. No difference was found among treatments in cvs. Fundacep 55 RR and Coodetec 214 RR, in the second sowing season. Perhaps, the occurrence of hail rain occurred at 04/21/2008 affected this variable. 1193 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 Table 2. Number of lesions cm2 of Asian rust on leaflets of six genotypes established in two sowing date, treated twice with the fungicides ciproconazol + azoxystrobin and epoxiconazol + pyraclostrobin, in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. Passo Fundo, RS, Brasil. Harvest 2007-2008 Fungicide Stage GENOTYPES A 4910 RG BMX Apolo RR A 6001 RR Fundacep 55 RR Coodetec 214 RR I II I II I II I II I II Untreated plants 1.23a 2.19a 0.02a 1.71a 2.84a 19.21a 13.61a 72.98a 2.19a 58.43a Azoxystrobin + Ciproconazol PRE + 21 days 0.06b 0.00b 0.03a 0.15a 0.66b 2.76c 0.07b 2.97b 0.42a 8,33b PRE + R5.1 0.06b 0.00b 0.04a 0.02a 0.05b 2.48c 0.02b 0.68b 0.51a 5,25b R1 + R5.1 0.00b 0.00b 0.02a 0.03a 0.02b 3.37c 0.06b 0.67b 0.03a 3,71b Pyraclostrobin + Epoxiconazol PRE + 21 days 0.06b 0.19b 0.03a 0.36a 0.28b 8.89b 1.10b 5.34b 0.26a 6,35b PRE + R5.1 0.18b 0.02b 0.03a 0.62a 0.29b 8.32b 0.10b 8.84b 1.39a 10,45b R1 + R5.1 0.18b 0.29b 0.03a 0.03a 0.08b 17.53a 0.38b 3.85b 0.05a 5,91b Means 0.24 0.37 0.03B 0.40A 0.57B 8.77A 2.02B 14.12A 0.71B 13.67A CV (%) 20.02 64.22 18.02 53.24 35.44 35.70 49.86 49.07 49.55 18.46 1 Means followed by lowercase and capital letters in the column and row, respectively, do not differ significantly by the Tukey test (p≤0.05). 1194 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 Table 3. Thousand grain weight (g) on plants of six genotypes established in two sowing date, treated twice with the fungicides ciproconazol + azoxystrobin and epoxiconazol + pyraclostrobin, in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. Passo Fundo, RS, Brasil. Harvest 2007-2008 Fungicide Stage GENOTYPES A 4910 RG BMX Apolo RR A 6001 RR Fundacep 55 RR Coodetec 214 RR I II I II I II I II I II Untreated plants 168.30c1 146.66c 157.68c 128.25c 134.35c 112.79c 155.18c 146.89bc 119.81b 99.20b Azoxystrobin + Ciproconazol PRE + 21 days 188.05b 164.63a 166.29b 146.82a 143.71b 132.36a 168.64b 151.16ab 129.45a 115,82a PRE + R5.1 185.24b 165.41a 171.39a 146.19a 141.35b 128.61a 174.15a 161.39a 133.85a 116,19a R1 + R5.1 196.63a 160.01a 179.78a 145.34a 146.03b 131.30a 174.03a 151.24ab 137.43a 114,84a Pyraclostrobin + Epoxiconazol PRE + 21 days 172.97c 160.73a 168.09b 136.72b 146.69b 120.41b 168.99b 148.89b 138.64a 109,98a PRE + R5.1 189.78b 161.71a 168.24b 134.36b 161.87a 128.80a 161.69b 140.08c 132.05a 109,38a R1 + R5.1 186.60b 157.79b 175.36a 144.20a 156.82a 124.10b 176.90a 146.31bc 127.76a 113,87a Means 183.94A 159.56B 169.55A 140.27B 147.26A 125.48B 168.51A 149.42B 131.28A 111.87B CV (%) 5.14 6.31 3.32 6.85 6.29 5.94 3.84 4.18 7.45 5.62 1 Means followed by lowercase and capital letters in the column and row, respectively, do not differ significantly by the Tukey test (p≤0.05). Table 4. Grain yield (kg ha-1) on plants of six genotypes established in two sowing date, treated twice with the fungicides ciproconazol + azoxystrobin and epoxiconazol + pyraclostrobin, in three moments 1: pre-closure of the space between the lines and 21 days after; 2: pre-closure of space between rows and R5.1 stage (10% of beginning seed); and 3: R1 (beginning bloom) and R5.1 stages. Passo Fundo, RS, Brasil. Harvest 2007-2008 Fungicide Stage GENOTYPES A 4910 RG BMX Apolo RR A 6001 RR Fundacep 55 RR Coodetec 214 RR I II I II I II I II I II Untreated plants 3122.43b1 2309.67b 2350.80b 2300.40b 2485.78c 1561.08b 3595.99b 864.81a 2186.79c 990.62a Azoxystrobin + Ciproconazol PRE + 21 days 3796.30a 3081.27a 3994.89a 3389.51a 3499.75b 2373.44a 4375.09a 821.17a 2575.16b 1251,42a PRE + R5.1 2998.97b 3266.46a 4022.42a 3402.56a 3206.28b 2191.79a 4351.98a 821.26a 2988.89a 1277,78a R1 + R5.1 3261.32b 3122.43a 4156.82a 3149.16a 3474.30b 2060.06a 4197.64a 995.53a 3018.31a 1123,73a Pyraclostrobin + Epoxiconazol PRE + 21 days 3240.74b 2937.24a 4052.01a 3044.34a 3859.14a 2128.31a 3816.18ab 883.39a 2834.07a 1200,92a PRE + R5.1 3708.85a 2906.38a 3952.58a 3380.09a 3807.93a 2183.81a 3598.04b 753.38a 2935.54a 1117,32a R1 + R5.1 3148.15b 2854.94a 3924.57a 3160.75a 3734.55a 2120.34a 4093.36a 891.67a 2951.45a 1306,23a Means 3325.25A 2925.48B 3779.16A 3118.12B 3409.67A 2088.40B 4001.18A 861.60B 2784.31A 1181.14B CV (%) 14.16 5.69 12.69 9.49 9.39 10.91 14.99 19.10 13.03 20.91 1 Means followed by lowercase and capital letters in the column and row, respectively, do not differ significantly by the Tukey test (p≤0.05). 1195 Chemical control of foliar diseases… DE ALMEIDA, R.; FORCELINI, C. A.; GARCÉS-FIALLOS, F. R. Biosci. J., Uberlândia, v. 33, n. 5, p. 1188-1196, Sept./Oct. 2017 A higher thousand grains weight and grain yield was observed in all genotypes planted in the second sowing season, compared to first one. Perhaps, both a higher disease intensity and late sowing may have contributed to reduction of productive potential. The vegetative and productive performance of soybean cultivars are influenced by the sowing date (PEREIRA-PEIXOTO et al., 2000; GALLOTI et al., 2005; GARCÉS-FIALLOS et al., 2014). Even this factor is the one that most influence on grain yield (PEREIRA-PEIXOTO et al., 2000). In this work was found an interaction among soybean genotypes and planting date in both sanitary and productivity variables. This should be taken into account to recommending the sowing season, as well as fungicides and application times, to control diseases such as Asian rust or powdery mildew. CONCLUSION Our results indicate that the chemical control of leaf diseases in soybean crop depends of the cultivar and sowing date. RESUMO: O objetivo foi estudar o efeito da aplicação antecipada de duas misturas de fungicidas no controle da ferrugem asiática e do oídio, bem como no rendimento de grãos em cinco cultivares de soja em duas épocas de semeadura. O experimento foi conduzido no campo experimental da FAMV/UPF. Utilizaram-se as cultivares A 4910 RG (super precoce), BMX Apolo RR, A 6001 RR e Fundacep 55 RR (precoces) e Coodetec 214 RR (moderado), estabelecidas em 13/11/2007 e 3/12/2007. Os fungicidas piraclostrobina + epoxiconazole e azoxistrobina + ciproconzole foram pulverizados duas vezes em 1: pré-fechamento do espaço entre as linhas e 21 dias após, 2: pré-fechamento do espaço entre as linhas e R5.1 (10% de granação), e 3: R1 (início da floração) e R5.1. Avaliaram-se a severidade (% da área foliar afetada) do oídio e o número de lesões cm2 da ferrugem asiática. Logo após as plantas foram colhidas, o peso de mil grãos (g) e rendimento de grãos (kg ha-1) foram quantificados. O delineamento experimental utilizado foi o de parcelas divididas com quatro repetições, onde a parcela principal foram as cinco cultivares, e as subparcelas foram o tratamento controle (plantas não tratadas) e os seis programas de controle químico. Para a separação das médias dos tratamentos e épocas, foram utilizados os testes de Tukey e t-Student (p≤0.05), respectivamente. De modo geral, a aplicação foliar de fungicidas controlou tanto a ferrugem asiática como o oídio, assim como também gerou um aumento do peso de mil grãos e rendimento de grãos. No entanto, parece existir uma interação entre os genótipos e data de semeadura. Assim, nossos resultados nos permitem inferir que o controle químico das doenças foliares na cultura da soja depende do cultivar e da data de semeadura. PALAVRAS-CHAVE: Glycine max L. Triazóis. Estrobilurinas. Oídio. Ferrugem asiática. 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