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The per cent disease intensity (PDI) was computed as per the formula suggested by Horsfall and Heuberger (1942).

Sum of all numerical ratings
PDI = ------------------------------------------------------------------------------- X 100
No. of leaves examined X maximum disease severity grade

Based on these observations, percent disease intensity (PDI) of two different types of leaf spots of soybean was recorded. The per cent disease intensity data was arcsine transformed before analysis of variance (ANOVA). Statistical analysis was done with using the standard procedure described by Gomez and Gomez (1986).

RESULTS AND DISCUSSION

The experiment was conducted successfully at ARS, SDAU, Ladol farm with susceptible variety NRC-37 of soybean. We visually observed two different types of leaf spots in the experiment. It was Alternaria leaf spot caused by Alternaria alternata (Fries) Keisslerand the other was cercospora or frog-eye leaf spot caused by Cercospora sojina Hara. The data on PDI of leaf spots (Alternaria & Cercospora) of soybean was recorded periodically at 60, 75 and 90 days after the sowing with consecutive three spray of fungicides (before and after seven days of spray) at 15 days interval and was found low to moderate in range. In Alternaria Leaf Spot (ALS) it was observed in 9.70-34.43 per cent range. Whereas, in case of Frog-eye Leaf Spot (FLS) it was observed with the range of 11.49-36.53 per cent. It has also been found that in all treatments PDI increased with the age of the plants. The data on disease intensity revealed that all fungicides tested reduced the disease intensity significantly as compared to control. Table 1 revealed that in case of Alternaria Leaf Spot (ALS) the minimum PDI was recorded after 7 days of first spray at 60 DAS in the treatment T6 i.e. spraying of pyraclostrobin 13.3% + epoxiconaxole 5% SE @ 0.01% (13.34%) followed by T1 i.e. hexaconazole 5% EC @ 0.005% (14.33%) which was found at par with T6 also then T5 kresoxim-methyl 44.3% SC @ 0.05% with its PDI 14.95 per cent. After 7 days of second spray at 75 DAS and third spray at 90 DAS the minimum PDI was recorded in the same trends. At 7 days after third spray, the minimum PDI was found in T6 (23.11%) followed by T1 and T5 which was found at par with their values 23.75, 34.78 per cent, respectively. (Table 1) Whereas, in case of Frog-eye Leaf Spot (FLS) or Cercospora Brown Leaf Spot, the minimum PDI was recorded after 7 days of first spray at 60 DAS in the treatment T6 i.e. spraying of pyraclostrobin 13.3% + epoxiconaxole 5% SE @ 0.01% (14.33%) followed by T1 i.e. hexaconazole 5% EC @ 0.005% (15.85%) and T5 i.e. kresoxim-methyl 44.3% SC @ 0.05% with its PDI 16.42 per cent. After 7 days of second spray at 75 DAS and third spray at 90 DAS the minimum PDI was recorded in the same trends. The minimum PDI, It was found in T6 (24.75%) with highest grain yield 1640 kg ha-1 followed by T1 and T5 which was found at par with their values 26.55, 27.49 per cent, respectively. The present study on efficacy of different fungicides with their doses against foliar fungal diseases of soybean revealed that the combination of two different group of fungicides i.e. pyraclostrobin 13.3% + epoxiconaxole 5% SE @ 0.01% was found very effective against Alternaria leaf spot & Frog-eye Leaf Spot of soybean and increasing the grain and haulm yield as compared to control. (Table 1).
For the management of frog-eye leaf spot in soybean, evaluation of resistant varieties is considered to be the most feasible and durable solution. Das et al. (2017) were screened out 26 varieties including one susceptible check against FLS under natural condition. Percent Disease Index was worked out and it varied from 4.00 % to 31.00 %. No variety was found Immune (Disease severity 0%). Fifteen varieties i.e., RKS 18, PK 564, PS 1241, PK 1092, Indira Soya 9, PS 1029, NRC 37, PS 1347, MAUS 71, PK 1024, PK 472,PK 416, Alankar, Ankur, JS 335 were observed to be resistant (Disease severity 1% to 10%). Eight varieties (NRC 37, PS 19, PK 327, RAUS 5, PK 1042, JS 9752, Shilajeet, JS -20-29) were categorized as moderately resistant (Disease severity 10% to 20%) and two varieties (Kalitur & Bragg) were showed under moderately susceptible (Disease severity 20% to 30%). Only one variety i. e., PK 262 was found susceptible (Disease severity 30% to 50%). None of the varieties was found highly susceptible (Disease severity above 50.1%). These resistant and moderately resistant varieties can be used as good donor for evolving resistant varieties against Frogeye leaf spot disease in soybean. Similar type of observation was done by Chandra, 2012.
In the year 2003, Prasad et al. conducted an experiment at ICAR Research Complex, Barapani for the management of two commonly occurring diseases like frog eye leaf spot and rust with different fungicides viz., propineb (antracol) @ 0.3%, tricyclazole (beam) @ 0.1 %, hexaconazole 5% EC (contaf 5E) @ 1%, tebuconazole (folicur) @ 0.2%, chlorothalonil 75% WP (kavach 75 WP) @ 0.2%, mancozeb 75% WP (indofil M-45) @ 0.25%, propiconazole 25% EC (tilt 25 EC) @ 0.1 %, benomyl (benlate) @ 0.2% and a neem product azardichtin (nimbicidin) @ 0.3% were evaluated against frog eye leaf spot and rust. They found that all the chemicals were effective against frog-eye leaf spot. Benomyl (12.2 PDI) was found best in reducing the frog eye leaf spot followed by chlorothalonil (13.6), mancozeb (15.4), tebuconazole (15.8), propicanazole and tricyclazole (17) however, these were at par with each other.
An experiment was conducted at AAU, Assam for identification of soybean diseases in assam region by Borah, M. (2019). Among foliar diseases,  Alternaria leaf spot appeared during first week of September vegetative growth stage of the crop whereas, Cercospora leaf spot (CLS) and Pod Blight[ PB (Ct)] were noticed at flowering and pod formation stage viz. September 25th  onward where intermittent rainfall was experienced by the crop. Whereas, in our experimental farm both the diseases were noticed at flowering and pod formation stage viz. September 25th onward.
Shivaprasad et al. (2021) studied on effect of fungicides on severity of coffee leaf rust and influence on yield of coffee. They found pyraclostrobin 133 g/l + epoxiconazole 50 g/l SE @ 1.5-4.5 ml/l recorded minimum severity of CLR diseases and maximum yield. Therefore, pyraclostrobin 133 g/l + epoxiconazole 50 g/l SE @ 1.5 ml/l can well be adopted as one of the component in developing integrated disease management strategies for minimizing the losses due to leaf rust (CLR) in Coffee.
Ribeiro et al. (2014) evaluated eight group of fungicides applied as seed treatment and aerial part of the soybean plants. They found that pyraclostrobin + methyl thiophanate favored root development on plantlets, plant height and grain yield, when it was applied on the soybean seeds. Fungicides applied on the plant aerial parts showed positive effects on control of foliar diseases in soybean.