The results of pooled data of two seasons pertaining to screening for biocontrol potential of different microbial isolates against major lepidopteran pests and per cent damage due to pod borers in soybean was recorded. Further, yield data was also recorded and presented here.
Spodoptera litura (Pooled)
During the period of experiment (Kharif, 2022 and 2023), the pooled mean larval population of S. litura was ranged between 9.25 to 11.25 larvae per meter row length. After imposition of treatment, the results of pooled data indicated that, significant reduction in larval population was registered in DBT-64 (200 ml/l) with the mean population of 2.32 larvae per mrl with 62.22 per cent reduction over control (% ROC) followed by DBT-80 at 200 ml/l (2.59 larvae/mrl and 57.86% ROC) which were statistically on par with each other. In contrast, control (6.15 larvae/mrl) plot recorded highest population followed by DBT-90 @ 100 (5.28 larvae/mrl). While, M. rileyi and spinosad recorded the mean population of 1.18 and 1.82 larvae /mrl and regarded as superior treatment over microbial isolates (Table 2).
Table 2
Effect of entomopathogenic microbial isolates against larval population of S. litura in soybean under field condition (Pooled)
Treatments /Isolates | Larval population after spray (No. of larvae/mrl) | Mean | Reduction over control (%) |
First spray | Second spray |
DBS | 3 DAS | 7 DAS | 10 DAS | DBS | 3 DAS | 7 DAS | 10 DAS |
T1- DBT-64 @ 100 ml/l | 9.59 (3.09) | 5.70 (2.38)c−f | 4.29 (2.03)d−f | 2.84 (1.69)f−h | 9.26 (3.03) | 5.00 (2.23)cde | 3.75 (1.93)c−f | 2.25 (1.47)de | 3.97 | 35.46 |
T2- DBT-64 @ 200 ml/l | 10.92 (3.30) | 3.75 (1.89)abc | 2.42 (1.44)bc | 1.50 (1.21)cde | 9.34 (3.06) | 3.00 (1.72)ab | 2.42 (1.53)abc | 0.85 (0.92)abc | 2.32 | 62.22 |
T3- DBT-80 @ 100 ml/l | 10.17 (3.18) | 6.00 (2.44)def | 4.67 (2.13)d−g | 2.92 (1.69)e−h | 9.84 (3.13) | 5.25 (2.28)cde | 4.09 (2.02)c−f | 2.33 (1.50)de | 4.21 | 31.59 |
T4- DBT-80 @ 200 ml/l | 9.25 (3.03) | 4.08 (1.98)a−d | 2.75 (1.57)bc | 1.75 (1.32)cde | 8.92 (2.97) | 3.30 (1.80)bc | 2.67 (1.61)bc | 1.00 (0.98)bc | 2.59 | 57.86 |
T5- DBT-90 @ 100 ml/l | 10.10 (3.15) | 6.83 (2.61)f | 5.93 (2.43)fg | 4.17 (2.04)hi | 9.77 (3.10) | 6.09 (2.47)de | 4.92 (2.22)ef | 3.75 (1.94)f | 5.28 | 14.15 |
T6- DBT-90 @ 200 ml/l | 11.09 (3.33) | 6.34 (2.51)def | 4.97 (2.20)efg | 3.08 (1.74)fgh | 10.76 (3.28) | 5.75 (2.40)de | 4.50 (2.11)def | 2.58 (1.59)de | 4.54 | 26.25 |
T7- AUUB-209 @ 100 ml/l | 10.25 (3.20) | 6.55 (2.55)f | 5.25 (2.28)efg | 3.75 (1.93)h | 9.92 (3.15) | 5.83 (2.41)de | 4.70 (2.17)def | 2.75 (1.66)ef | 4.81 | 21.87 |
T8- AUUB-209 @ 200 ml/l | 10.75 (3.27) | 4.42 (2.06)b−e | 3.25 (1.74)cd | 2.14 (1.43)def | 10.42 (3.22) | 4.30 (2.06)bcd | 2.92 (1.69)bcd | 1.58 (1.26)cd | 3.10 | 49.58 |
T9- NLE @ 100 ml/l | 10.83 (3.28) | 6.72 (2.59)ef | 5.67 (2.38)fg | 3.30 (1.82)gh | 10.50 (3.23) | 6.42 (2.53)de | 4.80 (2.16)def | 3.80 (1.94)f | 5.12 | 16.81 |
T10- NLE @ 200 ml/l | 10.10 (3.18) | 4.75 (2.15)b−f | 3.75 (1.89)c−e | 2.42 (1.53)d−g | 9.77 (3.12) | 4.50 (2.11)a−e | 3.38 (1.78)b−e | 1.92 (1.39)de | 3.45 | 43.86 |
T11- M. rileyi @ 2 g/l | 10.60 (3.26) | 3.43 (1.79)ab | 1.42 (1.13)ab | 1.00 (1.00)bc | 10.27 (3.20) | 2.17 (1.31)a | 2.08 (1.41)ab | 0.80 (0.89)ab | 1.82 | 70.47 |
T12- Spinosad 45 SC @ 0.2 ml/l | 10.09 (3.18) | 2.33 (1.50)a | 1.00 (0.98)a | 0.60 (0.74)a | 9.76 (3.12) | 1.68 (1.30)a | 1.10 (1.05)a | 0.35 (0.58)a | 1.18 | 80.84 |
T13- Control | 11.25 (3.35) | 7.15 (2.67)f | 6.50 (2.55)g | 5.75 (2.40)h | 10.58 (3.25) | 6.67 (2.58)e | 5.50 (2.34)f | 5.34 (2.31)g | 6.15 | |
S. Em.± | - | 0.17 | 0.15 | 0.12 | - | 0.16 | 0.09 | 0.11 | | |
CV (%) | 8.40 | 14.25 | 12.29 | 14.05 | 8.27 | 13.89 | 13.83 | 11.43 | | |
Figures in parentheses are √x + 0.5 transformed values; Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBS-Day Before Spray; DAS-Days After Spray; mrl: meter row length; DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp.) |
Thysanoplusia orichalcea (Pooled)
Before treatment, the mean larval population of T. orichalcea was ranged between 4.77 to 5.83 larvae per meter row length. After imposition of treatment, The lowest mean larval population and highest reduction over control was noticed in DBT-64 at 200 ml/l (2.52 larvae/ mrl and 62.00% ROC) followed by DBT-80 at 200 ml/l (2.80 larvae/ mrl and 57.81% ROC) which were statistically on par with each other. In contrast, control (6.63 larvae/mrl) plot recorded highest population followed by DBT-90 @ 100 (5.18 larvae/mrl). While, M. rileyi and spinosad recorded the lowest mean population of 2.07 and 1.37 larvae /mrl and regarded as superior treatment over microbial isolates (Table 3).
Table 3
Effect of entomopathogenic microbial isolates against larval population of T. orichalcea in soybean under field condition (Pooled)
Treatments /Isolates | Larval population after spray (No. of larvae/mrl) | Mean | Reduction over control (%) |
First spray | Second spray |
DBS | 3 DAS | 7 DAS | 10 DAS | DBS | 3 DAS | 7 DAS | 10 DAS |
T1- DBT-64 @ 100 ml/l | 4.94 (2.22) | 4.89 (2.21)cde | 4.17 (2.04)c−f | 3.42 (1.79)c−f | 4.59 (2.13) | 4.84 (2.19)d−f | 3.00 (1.73)c−f | 2.65 (1.63)de | 3.83 | 42.30 |
T2- DBT-64 @ 200 ml/l | 4.78 (2.18) | 3.80 (1.90)abc | 3.02 (1.66)a−c | 2.02 (1.42)a−c | 4.80 (2.19) | 3.19 (1.77)bc | 1.97 (1.40)bc | 1.14 (1.07)b | 2.52 | 62.00 |
T3- DBT-80 @ 100 ml/l | 5.69 (2.39) | 4.92 (2.22)cde | 4.37 (2.09)c−f | 3.83 (1.91)d−g | 4.59 (2.13) | 5.12 (2.26)d−f | 3.25 (1.74)c−f | 2.84 (1.69)de | 4.05 | 38.89 |
T4- DBT-80 @ 200 ml/l | 4.87 (2.20) | 4.17 (2.04)a−d | 3.34 (1.77)a−d | 2.27 (1.51)a−d | 5.08 (2.25) | 3.59 (1.88)bc | 2.17 (1.47)b−d | 1.27 (1.12)bc | 2.80 | 57.81 |
T5- DBT-90 @ 100 ml/l | 5.44 (2.33) | 5.97 (2.44)de | 5.37 (2.32)ef | 5.07 (2.25)g | 5.15 (2.26) | 6.12 (2.47)f | 4.38 (2.08)fg | 4.17 (2.03)f | 5.18 | 21.92 |
T6- DBT-90 @ 200 ml/l | 5.38 (2.32) | 5.20 (2.28)cde | 4.62 (2.14)def | 4.25 (2.06)efg | 4.70 (2.17) | 5.28 (2.30)ef | 3.42 (1.85)d−f | 2.08 (1.41)cd | 4.31 | 35.02 |
T7- AUUB-209 @ 100 ml/l | 5.46 (2.34) | 5.70 (2.39)de | 5.12 (2.26)ef | 4.63 (2.14)fg | 4.70 (2.17) | 5.79 (2.41)f | 4.17 (2.03)fg | 3.55 (1.87)ef | 4.83 | 27.23 |
T8- AUUB-209 @ 200 ml/l | 4.78 (2.19) | 4.53 (2.12)cd | 3.75 (1.94)b−e | 2.67 (1.63)b−e | 4.92 (2.21) | 3.92 (1.98)cd | 2.50 (1.53)b−d | 3.25 (1.79)ef | 3.27 | 50.68 |
T9- NLE @ 100 ml/l | 5.67 (2.38) | 5.72 (2.39)de | 5.05 (2.24)ef | 4.64 (2.15)fg | 5.70 (2.38) | 5.80 (2.40)f | 3.79 (1.95)ef | 3.42 (1.84)ef | 4.73 | 28.60 |
T10- NLE @ 200 ml/l | 4.77 (2.18) | 4.42 (2.09)bcd | 3.67 (1.86)b−e | 2.80 (1.66)b−e | 4.77 (2.18) | 4.17 (2.03)c−e | 2.42 (1.56)b−e | 3.22 (1.78)ef | 3.28 | 50.54 |
T11- M. rileyi @ 2 g/l | 4.86 (2.20) | 2.97 (1.65)ab | 2.50 (1.58)ab | 1.63 (1.27)ab | 4.62 (2.15) | 2.83 (1.66)ab | 1.67 (1.29)b | 0.85 (0.92)ab | 2.07 | 68.72 |
T12- Spinosad 45 SC @ 0.2 ml/l | 4.87 (2.20) | 2.10 (1.42)a | 1.83 (1.35)a | 1.30 (1.14)a | 4.72 (2.17) | 1.94 (1.39)a | 0.67 (0.82)a | 0.40 (0.62)a | 1.37 | 79.30 |
T13- Control | 5.83 (2.41) | 7.00 (2.65)e | 5.97 (2.44)f | 7.84 (2.80)h | 6.00 (2.44) | 7.75 (2.78)g | 5.63 (2.37)g | 5.61 (2.37)g | 6.63 | |
S. Em.± | - | 0.15 | 0.15 | 0.14 | - | 0.10 | 0.13 | 0.10 | | |
CV (%) | 8.53 | 12.78 | 13.79 | 14.08 | 8.20 | 8.47 | 14.29 | 12.58 | | |
Figures in parentheses are √x + 0.5 transformed values; Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBS-Day Before Spray; DAS-Days After Spray; mrl: meter row length; DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp. |
Spilosoma obliqua (Pooled)
The mean larval population of S. obliqua was ranged between 4.77 to 5.83 larvae per meter row length. After imposition of treatment, DBT-64 and DBT-80 at 200 ml/l emerged as superior treatments by recording the lowest mean population of 1.17 and 1.34 larvae per meter row length with the reduction over control of 66.28 and 61.48 per cent, respectively. While, AUUB-209 and neem leaf endophyte (200 ml/l) recorded the mean population of 1.67 and 1.68, respectively. In contrast, highest population was recorded in control (3.48 larvae/ mrl) (Table 4).
Table 4
Effect of entomopathogenic microbial isolates against larval population of S. obliqua in soybean under field condition (Pooled)
Treatments /Isolates | Larval population after spray (No. of larvae/mrl) | Mean | Reduction over control (%) |
First spray | Second spray |
DBS | 3 DAS | 7 DAS | 10 DAS | DBS | 3 DAS | 7 DAS | 10 DAS |
T1- DBT-64 @ 100 ml/l | 3.23 (1.80) | 2.50 (1.56)de | 2.22 (1.46)def | 1.98 (1.40)d−f | 2.77 (1.66) | 1.85 (1.36)de | 1.58 (1.26)de | 1.44 (1.19)ef | 1.93 | 44.63 |
T2- DBT-64 @ 200 ml/l | 3.33 (1.83) | 1.83 (1.35)abc | 1.28 (1.13)abc | 1.05 (1.02)bc | 2.73 (1.65) | 1.18 (1.08)b | 0.97 (0.99)b | 0.73 (0.85)b | 1.17 | 66.28 |
T3- DBT-80 @ 100 ml/l | 3.23 (1.80) | 2.67 (1.61)de | 2.30 (1.49)def | 2.17 (1.47)b−f | 2.84 (1.69) | 1.97 (1.40)e | 1.75 (1.32)ef | 1.58 (1.25)fg | 2.07 | 40.46 |
T4- DBT-80 @ 200 ml/l | 3.30 (1.82) | 2.02 (1.39)a−d | 1.50 (1.23)a−d | 1.28 (1.12)c | 2.77 (1.66) | 1.33 (1.15)bc | 1.08 (1.04)bc | 0.84 (0.91)bc | 1.34 | 61.48 |
T5- DBT-90 @ 100 ml/l | 3.35 (1.83) | 3.47 (1.86)ef | 2.82 (1.66)ef | 2.67 (1.63)g | 2.85 (1.69) | 2.67 (1.63)g | 2.42 (1.55)h | 2.25 (1.50)h | 2.71 | 22.08 |
T6- DBT-90 @ 200 ml/l | 3.30 (1.82) | 3.00 (1.73)def | 2.44 (1.54)de | 2.20 (1.48)ef | 2.84 (1.69) | 2.17 (1.47)ef | 1.89 (1.37)e−g | 1.75 (1.32)fg | 2.24 | 35.68 |
T7- AUUB-209 @ 100 ml/l | 3.27 (1.81) | 3.17 (1.77)def | 2.52 (1.57)de | 2.42 (1.55)fg | 2.80 (1.67) | 2.47 (1.57)fg | 2.17 (1.47)gh | 2.00 (1.41)gh | 2.46 | 29.49 |
T8- AUUB-209 @ 200 ml/l | 3.30 (1.82) | 2.33 (1.50)c−e | 1.93 (1.39)b−e | 1.75 (1.32)d | 2.77 (1.66) | 1.58 (1.26)cd | 1.33 (1.15)cd | 1.08 (1.04)b−d | 1.67 | 52.09 |
T9- NLE @ 100 ml/l | 3.41 (1.85) | 3.22 (1.79)ef | 2.55 (1.58)ef | 2.42 (1.55)fg | 2.84 (1.69) | 2.42 (1.56)fg | 2.08 (1.44)def | 2.00 (1.41)gh | 2.45 | 29.74 |
T10- NLE @ 200 ml/l | 3.33 (1.83) | 2.33 (1.50)c−e | 1.97 (1.37)b−e | 1.79 (1.33)de | 2.75 (1.66) | 1.58 (1.26)cd | 1.33 (1.15)cd | 1.08 (1.04)c−e | 1.68 | 51.77 |
T11- M. rileyi @ 2g/l | 3.26 (1.81) | 1.57 (1.25)ab | 1.15 (1.07)ab | 0.88 (0.93)ab | 2.75 (1.66) | 1.08 (1.04)ab | 0.85 (0.92)ab | 0.52 (0.71)ab | 1.01 | 71.06 |
T12- Spinosad 45 SC @ 0.2 ml/l | 3.27 (1.81) | 1.35 (1.16)a | 0.78 (0.88)a | 0.42 (0.63)a | 2.82 (1.68) | 0.88 (0.94)a | 0.63 (0.79)a | 0.27 (0.52)a | 0.72 | 79.26 |
T13- Control | 3.42 (1.85) | 4.52 (2.13)f | 3.38 (1.84)f | 3.25 (1.80)h | 3.30 (1.82) | 3.34 (1.83)h | 3.42 (1.85)i | 3.00 (1.73)i | 3.48 | |
S. Em.± | - | 0.10 | 0.12 | 0.08 | - | 0.11 | 0.08 | 0.05 | | |
CV (%) | 8.30 | 12.10 | 13.14 | 8.6 | 9.2 | 8.96 | 8.05 | 8.63 | | |
Figures in parentheses are √x + 0.5 transformed values; Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBS-Day Before Spray; DAS-Days After Spray; mrl: meter row length; DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp.) |
Defoliation (%) due to defoliators
Leaf feeding of soybean leaves by insects leading to defoliation, is the most commonly observed type of soybean insect injury, but soybean plants have the ability to compensate for insect defoliation. When making pest-management decisions, a crucial consideration is the size of the remaining leaf canopy and the growth stage of the crop. The results of pooled analysis of per cent defoliation caused due to defoliators revealed that, lowest defoliation was recorded in DBT-64 (200 ml/l) with 12.87 per cent followed by DBT-80 @ 200 ml/l (30.21%). Whereas, M. rileyi and spinosad registered the defoliation per cent to the extent of 11.67 and 7.81, respectively. However, highest defoliation was noticed in control (43.39%) followed by DBT-90 (35.89%) (Table 5).
Table 5
Effect of different microbial isolates on defoliation due to defoliators in soybean (Pooled)
Treatments /Isolates | Leaf damage (%) * | Mean | Reduction over control (%) |
DBS | After first spray | After second spray |
T1- DBT-64 @ 100 ml/l | 39.10 (38.70) | 27.66 (31.73)g | 24.83 (29.89)g | 27.59 | 36.43 |
T2- DBT-64 @ 200 ml/l | 38.73 (38.49) | 12.83 (20.99)c | 11.56 (19.88)c | 12.87 | 70.34 |
T3- DBT-80 @ 100 ml/l | 39.39 (38.87) | 30.34 (33.42)h | 27.34 (31.53)h | 30.21 | 30.37 |
T4- DBT-80 @ 200 ml/l | 38.62 (38.42) | 16.53 (23.99)d | 14.21 (22.15)d | 16.64 | 61.64 |
T5- DBT-90 @ 100 ml/l | 40.09 (39.28) | 35.92 (36.82)l | 32.85 (34.97)k | 35.89 | 17.29 |
T6- DBT-90 @ 200 ml/l | 38.77 (38.51) | 31.19 (33.95)i | 28.52 (32.28)i | 31.26 | 27.96 |
T7- AUUB-209 @ 100 ml/l | 39.33 (38.84) | 32.72 (34.89)j | 29.00 (32.58)i | 32.62 | 24.83 |
T8- AUUB-209 @ 200 ml/l | 39.27 (38.80) | 22.58 (28.37)e | 20.24 (26.74)e | 22.47 | 48.22 |
T9- NLE @ 100 ml/l | 38.67 (38.45) | 34.39 (35.90)k | 29.72 (33.04)j | 34.43 | 20.65 |
T10- NLE @ 200 ml/l | 39.05 (38.68) | 25.17 (30.11)f | 22.67 (28.43)f | 25.11 | 42.14 |
T11- M. rileyi @ 2g/l | 38.67 (38.45) | 11.56 (19.88)b | 8.17 (16.61)b | 11.67 | 73.10 |
T12- Spinosad 45 SC @ 0.2 ml/l | 39.04 (38.67) | 8.00 (16.43)a | 6.33 (14.57)a | 7.81 | 81.99 |
T13- Control | 40.18 (39.34) | 43.39 (41.20)m | 43.82 (41.45)l | 43.39 | |
S. Em.± | - | 0.12 | 0.12 | | |
CV (%) | 7.07 | 7.01 | 817 | | |
*Mean of three observations recorded at 3, 7 and 10 DAS; Values in parentheses are the arc sine transformed values. Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBS: Day Before Spray; DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp.) |
Cydia ptychora (Pooled)
The results of pooled data of C. ptychora incidence during 2022 and 2023 revealed that, lowest larval population was registered in DBT-64 (200 ml/l) with the mean population of 1.07 larvae per five pods followed by DBT-80 @ 200 ml/l (1.24 larvae/5 pods) with reduction over control of 60.87 and 54.67 per cent, respectively (Table 6).
Table 6
Effect of entomopathogenic microbial isolates against larval population of Cydia ptychora in soybean (Pooled)
Treatments /Isolates | No. of larvae/ 5 pods | Mean | Reduction over control (%) |
DBS | 65 DAS | 75 DAS | 85 DAS |
T1- DBT-64 @ 100 ml/l | 4.22 (2.04) | 1.33 (1.15)efg | 1.79 (1.30)c−e | 2.43 (1.54)c−f | 1.85 | 32.46 |
T2- DBT-64 @ 200 ml/l | 4.47 (2.11) | 0.70 (0.83)c | 0.87 (0.93)ab | 1.67 (1.25)abc | 1.07 | 60.87 |
T3- DBT-80 @ 100 ml/l | 4.60 (2.14) | 1.38 (1.17)hij | 1.91 (1.38)d−f | 2.50 (1.58)def | 1.93 | 29.44 |
T4- DBT-80 @ 200 ml/l | 4.46 (2.11) | 0.80 (0.89)cd | 1.09 (1.04)bc | 1.83 (1.35)a−d | 1.24 | 54.76 |
T5- DBT-90 @ 100 ml/l | 4.04 (2.01) | 1.97 (1.40)ij | 2.72 (1.63)f | 3.08 (1.76)ef | 2.59 | 5.52 |
T6- DBT-90 @ 200 ml/l | 4.13 (2.03) | 1.50 (1.21)f−i | 2.08 (1.44)d−f | 2.42 (1.55)c−f | 2.00 | 27.03 |
T7- AUUB-209 @ 100 ml/l | 4.69 (2.17) | 1.67 (1.29)g−i | 2.25 (1.50)ef | 2.92 (1.71)ef | 2.28 | 16.87 |
T8- AUUB-209 @ 200 ml/l | 3.96 (1.99) | 1.00 (1.00)c−e | 1.67 (1.29)c−e | 2.09 (1.45)b−e | 1.58 | 42.19 |
T9- NLE @ 100 ml/l | 4.54 (2.13) | 1.80 (1.34)hij | 2.50 (1.58)ef | 3.05 (1.74)ef | 2.45 | 10.56 |
T10- NLE @ 200 ml/l | 4.13 (2.03) | 1.17 (1.08)def | 1.50 (1.21)cd | 2.50 (1.58)def | 1.72 | 37.19 |
T11- M. rileyi @ 2 g/l | 4.38 (2.09) | 0.42 (0.64)b | 0.75 (0.86)ab | 1.39 (1.17)ab | 0.85 | 68.98 |
T12- Spinosad 45 SC @ 0.2 ml/l | 3.98 (2.00) | 0.19 (0.43)a | 0.58 (0.75)a | 1.22 (1.10)a | 0.66 | 75.87 |
T13- Control | 4.59 (2.14) | 2.34 (1.53)j | 2.55 (1.60)f | 3.34 (1.83)f | 2.74 | |
S. Em.± | - | 0.06 | 0.08 | 0.10 | | |
CV (%) | 9.40 | 10.53 | 12.19 | 12.24 | | |
Figures in parentheses are √x + 0.5 transformed values; Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBS-Day Before Spray; DAS-Days After Spray; DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp.) |
Pod damage (%) (pooled)
The results of pooled analysis of pod damage revealed that, lowest pod damage was noticed in DBT-64 @ 200 ml/l (17.33%) followed by DBT-80 @ 200 ml/l (18.59%). The next best treatments were AUUB-209 and neem leaf endophyte @ 200 ml/l with mean pod damage of 22.08 and 24.34 per cent. Whereas, M. rileyi and spinosad recorded least pod damage with 12.25 and 8.28 per cent, respectively (Table 7).
Table 7
Influence of different microbial isolates on pod damage and grain yield of soybean
Treatments /Isolates | Pooled |
*Pod damage (%) | Yield (q/ ha) |
T1- DBT-64 @ 100 ml/l | 28.34 (32.16)g | 14.86a |
T2- DBT-64 @ 200 ml/l | 17.33 (24.60)c | 18.17b |
T3- DBT-80 @ 100 ml/l | 33.10 (35.12)h | 14.44c |
T4- DBT-80 @ 200 ml/l | 18.59 (25.54)d | 16.58d |
T5- DBT-90 @ 100 ml/l | 48.50 (44.14)l | 11.10e |
T6- DBT-90 @ 200 ml/l | 43.00 (40.98)k | 12.78f |
T7- AUUB-209 @ 100 ml/l | 39.34 (38.85)i | 13.17g |
T8- AUUB-209 @ 200 ml/l | 22.08 (28.03)e | 15.71h |
T9- NLE @ 100 ml/l | 41.00 (39.82)j | 12.09i |
T10- NLE @ 200 ml/l | 24.34 (29.56)f | 15.32j |
T11- M. rileyi @ 2 g/l | 12.25 (20.49)b | 19.17k |
T12- Spinosad 45 SC @ 0.2 ml/l | 8.28 (16.72)a | 20.17l |
T13- Control | 88.00 (69.73)m | 6.67m |
S. Em.± | 0.12 | 0.12 |
CV (%) | 8.6 | 10.47 |
*Values in parentheses for pod damage are the arc sine transformed values. Means in the columns followed by the same alphabet do not differ significantly by DMRT (P = 0.05); DBT-64: Streptomyces hyderabadensis, DBT-80: Streptomyces xiaminensis, DBT-90 (Unidentified), AUUB-209: Streptomyces enissocaesilis and NLE: neem leaf endophyte (Streptomyces sp.) |
Grain yield (Pooled)
The efficacy of different microbial isolates against all the insect pests in soybean reflected in terms of yield. Pooled data of two season for soybean grain yield indicated that, highest grain yield was obtained in plot treated with DBT-64 @ 200 ml/l with 18.17 q/ha which was regarded as significantly superior treatment among all the treatments followed by DBT-80 @ 200 ml/l (16.58 q/ha) which were on par with each other. In contrast, lowest yield was registered in control plot (6.67 q/ha). Whereas, spinosad and M. rileyi registered highest yield of 19.17 and 20.17 q/ha, respectively which were regarded as superior over microbial isolates (Table 7).
During the recent past, Streptomycetes have been considered as a prospective biocontrol agent in agriculture especially with respect to management of insect pests. Hence, the literature regarding the utilization of microbial (actinobacterial) inoculants in pest control is very meagre; other related reviews were considered for discussion with the results of present investigation.
Arun (2022) isolated actinobacteria, DBT-64 and DBT-80 from soil and identified as Streptomyces hyderabadensis and Streptomyces xiaminensis. Superiority of these isolates is due to the most striking feature of these organisms i.e., their ability to produce secondary metabolites. LC-MS analysis results revealed that the metabolites mainly consist of terpenoids, oxidized fatty acids, alkaloids, alkylglucosinolates, bipyridines, oligopyridines, benzopyranoids, class 3 linoleic acid and other functional groups. Suma (2022) reported that, secondary metabolites produced by the Streptomyces sp., coumaroyl tyramine, linoleic acid, cis, trans-farnesyl acetate, benzyl glucosinolate oleanane and scaposin, were having an insecticidal activity against S. litura, P. xylostella and S. frugiperda.
Several Streptomyces metabolites such as avermectin, emamectin, milbemycin and spinosyns have been documented as potential protective agents against a variety of insect pests. They involved in disruption of nicotinic acetylcholine receptors. Their insecticidal activity, unique mode of action and lower environmental effects make them useful novel agents for modern integrated pest management (Kirst, 2010). Among the microbes actinobacteria are reported to produce about 45 per cent of the bioactive compounds and 80 per cent of antibiotics are available in the genera Micromonospora and Streptomyces sp. These are capable of producing antibiotics and bioactive compounds like lomofungin, spoaxmicin, sclerothricin, antimycin, rosamicin, validamycin and rifamycin. Several Streptomyces metabolites have been identified as possible protective agents against a variety of insect pests such as ivermectin, emamectin benzoate, polynactin, milbemycin and spinosad (Moncheva et al., 2002).
Similar kind of results were obtained by (Padanad and Krishnaraj, 2009) who conducted experiment using biopesticides with N. rileyi which were active against third instars of S. litura, resulting in 85 to 97 per cent mortality. Patil et al (2014) stated that early instars were highly susceptible with a mortality of 70.17 per cent, which decreased significantly as the age of the larvae advanced. The results of the Ahirwar et al. (2013) also in agreement with the present findings who tested microbial entomopathogens revealed that Bacillus thuringiensis var. kurstaki (4.26 larvae/mrl) was found to be most effective followed by B. bassiana (5.06 larvae/mrl), M. anisopliae (6.06 larvae/mrl), Spinosad 45 SC (6.40 larvae/mrl) and Dipel (7.56 larvae/mrl). Similarly, Balikayi et al., (2021) opinioned that biopesticides, B. thuringiensis var. kurstaki (Btk) found to be effective treatment against defoliators in soybean which given the grain yield of 16.85 q/ha followed by M. rileyi + Btk (15.47 q/ha) and M. rileyi (13.55 q/ha). These results are partially supporting to the results of the present investigation.
Metarhizium rileyi is known to be a potent entomopathogen against lepidopteran pests of soybean was endorsed by many researchers (Lingappa et al., 2000; Patil, 2002 and Patil and Abhilash, 2014). Spinosad had suppressed all the lepidopteran pest population in soybean and consistently maintained its superiority among all the treatments. The effectiveness of spinosad against lepidopteran pests especially in soybean crop was well documented by Chaudhary and Meghwal (2013); Lakshman et al. (2017); Patil et al. (2014); Patidar and Kumar (2018); Ahirwar et al. (2013); Sonkamble et al. (2018). Mode of action of spinosad is to alter the function of nicotinic and GABA gated ion channels, causing rapid excitation of the insect nervous system, leading to involuntary muscle contractions, tremors, paralysis and death (Salgado, 1998).