Efficacy of Lab bioassay
The largest larval mortality was recorded in 3rd instar T. absoluta larvae, and the therapy was superior. The treatment with H. indica at 160 IJs/cm2 resulted in the highest percent larvae mortality, with 90.00 percent larval mortality, followed by S. feltiae at 160 IJs/cm2 (85.38 percent). The next best treatments, in order of efficacy, were H. indica at 80 IJs/cm2 (74.12 percent), S. feltiae at 80 IJs/cm2 (69.50 percent), and H. indica at 80 IJs/cm2 (74.12 percent) (Table 2). The mortality rate of larvae ranged from 31.53 to 90.00 percent. The highest larval mortality of 4th instar T. absoluta larvae was recorded, and it was discovered to be the most superior treatment. The treatment with S. feltiae at 160 IJs/cm2 resulted in the highest percent larvae mortality, with 90.00 percent larval mortality, followed by H. indica at 160 IJs/cm2 (80.76 percent) (Fig. 4). The next best treatments, in order of efficacy, were S. feltiae at 80 IJs/cm2 (74.12 percent), H. indica at 80 IJs/cm2 (67.84 percent), and H. indica at 80 IJs/cm2 (67.84 percent) (Table 2).
Bioassay of larvicidal activity
Tuta absoluta 3rd instar larvae had LC50 of 19.29 IJs/cm2, 08.55 IJs/cm2, LC75 of IJs/cm2, 83.12 IJs/cm2, 40.47 IJs/cm2, and LC90 of IJs/cm2, 50.44 IJs/cm2, 78.89 IJs/cm2, respectively, for 48 hours. LC50 of 07.52 IJs/cm2, 05.42 IJs/cm2, LC75 of 25.42 IJs/cm2, 20.70 IJs/cm2, and LC90 of 26.03 IJs/cm2, 69.19 IJs/cm2 for 72 h exposure (Fig 1) (Table 3). T. absoluta 4th instar larvae had LC50 of 09.32 IJs/cm2, 13.90 IJs/cm2, LC75 of IJs/cm2, 48.17 IJs/cm2, 60.10 IJs/cm2, and LC90 of IJs/cm2, 74.18 IJs/cm2, 76.43 IJs/cm2, respectively, for 48 hours. LC50 of 05.89 IJs/cm2, 08.92 IJs/cm2, LC75 of 20.29 IJs/cm2, 32.61 IJs/cm2, and LC90 of 61.71 IJs/cm2, 56.63 IJs/cm2 for 72 h exposure (Fig 2) (Table 3).
Table 2.
Larvicidal activity of tested nematode strain against tomato pinworm 3rd and 4th instar larva stage mortality (%) mean performance
3rd Instar of Tuta absoluta
|
|
(4th) Final instar of Tuta absoluta
|
|
Tuta absoluta mortality (%) 24 hrs after treatment
|
|
|
Tuta absoluta mortality (%) 24 hrs after treatment
|
|
Treatment
|
Steinernema feltiae
|
|
Heterorhabditis indica
|
Mean
|
|
Steinernema feltiae
|
|
Heterorhabditis indica
|
Mean
|
|
24 hrs
|
48 hrs
|
72 hrs
|
|
24 hrs
|
48 hrs
|
72 hrs
|
|
24 hrs
|
48 hrs
|
72 hrs
|
|
24 hrs
|
48 hrs
|
72 hrs
|
Control
|
0.00
|
0.00
|
0.00
|
|
0.00
|
0.00
|
0.00
|
0.00
|
|
0.00
|
0.00
|
0.00
|
|
0.00
|
0.00
|
0.00
|
0.00
|
|
(0.00)*
|
(0.00)
|
(0.00)
|
|
(0.00)
|
(0.00)
|
(0.00)
|
(0.00)
|
|
(0.00)
|
(0.00)
|
(0.00)
|
|
(0.00)
|
(0.00)
|
(0.00)
|
(0.00)
|
10 IJs/cm2
|
17.50
|
37.50
|
57.50
|
|
30.00
|
55.00
|
65.00
|
43.75
|
|
30.00
|
50.00
|
60.00
|
|
27.50
|
42.50
|
52.50
|
43.75
|
|
(24.15)
|
(37.64)
|
(49.30)
|
|
(33.04)
|
(47.86)
|
(53.75)
|
(40.95)
|
|
(33.04)
|
(44.98)
|
(50.87)
|
|
(31.53)
|
(40.59)
|
(46.42)
|
(41.23)
|
20 IJs/cm2
|
27.50
|
50.00
|
70.00
|
|
40.00
|
62.50
|
72.50
|
53.75
|
|
42.50
|
62.50
|
77.50
|
|
42.50
|
57.50
|
67.50
|
58.33
|
|
(31.38)
|
(44.98)
|
(56.92)
|
|
(39.15)
|
(52.31)
|
(58.58)
|
(47.22)
|
|
(40.65)
|
(52.25)
|
(61.74)
|
|
(40.59)
|
(49.30)
|
(55.26)
|
(49.96)
|
40 IJs/cm2
|
45.00
|
65.00
|
82.50
|
|
50.00
|
75.00
|
82.50
|
66.66
|
|
50.00
|
75.00
|
85.00
|
|
50.00
|
67.50
|
77.50
|
67.50
|
|
(42.03)
|
(53.75)
|
(65.44)
|
|
(44.98)
|
(60.61)
|
(68.76)
|
(55.92)
|
|
(44.98)
|
(60.24)
|
(67.47)
|
|
(44.98)
|
(55.26)
|
(61.74)
|
(55.77)
|
80 IJs/cm2
|
55.00
|
75.00
|
87.50
|
|
62.50
|
80.00
|
90.00
|
75.00
|
|
57.50
|
80.00
|
90.00
|
|
60.00
|
75.00
|
85.00
|
74.58
|
|
(47.86)
|
(60.08)
|
(69.50)
|
|
(52.31)
|
(63.78)
|
(74.12)
|
(61.27)
|
|
(49.37)
|
(66.73)
|
(74.12)
|
|
(50.81)
|
(60.24)
|
(67.84)
|
(61.51)
|
160 IJs/cm2
|
65.00
|
82.50
|
97.50
|
|
75.00
|
92.50
|
100.00
|
85.41
|
|
67.50
|
87.50
|
100.00
|
|
72.50
|
87.50
|
95.00
|
85.00
|
|
(53.91)
|
(65.44)
|
(85.38)
|
|
(60.08)
|
(76.15)
|
(90.00)
|
(71.82)
|
|
(55.26)
|
(72.46)
|
(90.00)
|
|
(58.42)
|
(69.50)
|
(80.76)
|
(71.06)
|
Mean
|
35.00
|
51.66
|
65.83
|
|
42.91
|
60.83
|
68.33
|
|
|
41.21
|
59.16
|
68.75
|
|
42.08
|
55.00
|
62.91
|
|
|
(33.22)
|
(43.65)
|
(54.42)
|
|
(38.26)
|
(50.12)
|
(57.53)
|
|
|
(37.21)
|
(49.44)
|
(57.36)
|
|
(37.72)
|
(45.81)
|
(52.00)
|
|
LSD (p< 0.05)
|
9.03
|
6.68
|
7.56
|
|
6.66
|
9.55
|
12.59
|
|
|
6.05
|
13.76
|
8.77
|
|
6.08
|
6.28
|
9.03
|
|
*Figures in parentheses are arc sine transformed values
Table 3.
Log probit analysis of larvicidal activity of tested nematode strain against tomato pinworm instars, 3rd and 4th stage
Stage of Insect
|
Nematode sp.
|
Exposure Time (hr)
|
LC50 (IJs/cm2)
95% LCl-UCL
|
LC75 (IJs/cm2)
95% LCl-UCL
|
LC90 (IJs/cm2)
95% LCl-UCL
|
Intercept
|
Slope
|
χ2 value
|
P-value
|
III- instar
|
S. feltiae
|
48
|
19.29 (12.83 - 29.01)
|
83.12 (55.28 - 24.99)
|
50.44 (25.79 - 65.31)
|
-1.36
|
0.23
|
0.27
|
0.004**
|
72
|
07.52 (05.11 - 11.07)
|
25.42 (17.27 - 37.41)
|
26.03 (51.66 - 11.89)
|
-1.11
|
0.25
|
2.06
|
0.012*
|
III- instar
|
H. indica
|
48
|
08.55 (05.42 - 13.51)
|
40.47 (25.63 - 63.90)
|
78.89 (10.79 - 58.77)
|
-0.93
|
0.23
|
1.99
|
0.018*
|
72
|
05.42 (03.51 - 08.36)
|
20.70 (13.41 - 31.97)
|
69.19 (44.81 - 17.83)
|
-0.85
|
0.26
|
1.85
|
0.032*
|
IV- instar
|
S. feltiae
|
48
|
09.32 (05.80 - 14.98)
|
48.17 (29.98 - 77.41)
|
74.18 (31.42 - 39.34)
|
-0.91
|
0.23
|
0.46
|
0.018*
|
72
|
05.89 (03.92 - 08.85)
|
20.29 (13.51 - 30.47)
|
61.71 (41.09 - 92.68)
|
-0.96
|
0.26
|
1.53
|
0.022*
|
IV- instar
|
H. indica
|
48
|
13.90 (09.16 - 21.10)
|
60.10 (39.60 - 91.20)
|
76.43 (47.89 - 40.56)
|
-1.21
|
0.23
|
2.18
|
0.007**
|
72
|
08.92 (06.01 - 13.24)
|
32.61 (21.98 - 48.38)
|
56.63 (70.52 - 55.23)
|
-1.14
|
0.24
|
1.02
|
0.010*
|
- EPNs suspensions were administered at a concentration of (IJs/cm2).
- Lethal Concentration are calculated by Probit Methods.
- Significant differences from control are indicated (**P < 0.01; *P < 0.05).
|
Efficacy of Greenhouse Tests
The survival population of the tomato leafminer Tuta absoluta on tomato one day before, three, seven, ten, and fourteen days after the first spray was presented in (Table 2). The average number of T. absoluta larvae that survived one day before being sprayed ranged from 5.77 to 7.36 larvae per plant. The pre-treatment data was determined to be non-significant, indicating that the pest population in the experimental plot was uniform. A small increase in the larval population was seen in all treated plots 14 days after the first spray. The average number of larvae that survived each plant ranged from 1.31 to 2.13. The maximum number of larvae per plant was found in the untreated control plot, which had 4.09 larvae per plant. Treatment with H. indica at 1,00,000 IJs/cm2 (1.31 larvae/plant) was shown to be consistently effective against T. absoluta, followed by treatment with H. indica at 2,00,000 IJs/cm2 (1.42 larvae/plant). Treatments with S. feltiae at 1,00,000 IJs/cm2 (1.59 larvae/plant) and S. feltiae at 2,00,000 IJs/cm2 (1.68 larvae/plant) were the next in order of efficacy, with no significant differences between them.
Overall, the efficacy results showed that H. indica at 1,00,000 IJs/cm2 (1.78 larvae/plant) was the most successful treatment in lowering the T. absoluta surviving population when compared to other treatments. The next most successful treatment was S. feltiae at a rate of 1,00,000 IJs/cm2 (1.97 larvae/plant). In order of efficacy, H. indica was next with 2,00,000 IJs/cm2 (2.00 larvae/plant). A small increase in the larval population was seen in all of the treated plots 14 days after the second spray. The average number of larvae survival populations per plant ranged from 1.18 to 1.51. It was found to be the highest in the untreated control plot, with 4.24 larvae per plant. Treatment with H. indica at 2,00,000 IJs/cm2 (1.18 larvae/plant) was shown to be consistently effective against T. absoluta, as was treatment with S. feltiae at 2,00,000 IJs/cm2 (1.38 larvae/plant). Treatments with H. indica at 1,00,000 IJs/cm2 (1.45 larvae/plant), H. indica at 4,00,000 IJs/cm2 (1.48 larvae/plant), and H. indica at 4,00,000 IJs/cm2 (1.48 larvae/plant) were the next in order of efficacy, and there were no significant differences in the remaining treatments.
Thus, the treatment with H. indica at 2,00,000 IJs/cm2 (1.60 larvae/plant) was shown to be superior than H. indica at 1,00,000 IJs/cm2 (1.66 larvae/plant) and H. indica at 4,00,000 IJs/cm2 (1.77 larvae/plant) in terms of overall performance. S. feltiae at 1,00,000 IJs/cm2 (1.84 larvae/plant), S. feltiae at 2,00,000 IJs/cm2 (1.85 larvae/plant), and S. feltiae at 4,00,000 IJs/cm2 (2.06 larvae/plant) were all shown to be similarly effective in lowering the T. absoluta population. A small increase in the larval population was seen in all of the treated plots at 14 DAS of the third spray. The average number of larvae survival populations per plant ranged from 1.02 to 1.98. The maximum number of larvae per plant was found in the untreated control plot, at 4.92. Treatment with H. indica at 4,00,000 IJs/cm2 (1.02 larvae/plant) was shown to be consistently effective against T. absoluta, as did treatment with H. indica at 2,00,000 IJs/cm2 (1.09 larvae/plant). Treatments with S. feltiae at 2,00,000 IJs/cm2 (1.17 larvae/plant), S. feltiae at 1,00,000 IJs/cm2 (1.34 larvae/plant), and S. feltiae at 4,00,000 IJs/cm2 (1.53 larvae/plant) were found to be equally successful, as were treatments with H. indica at 1,00,000 IJs/cm2. The treatments, on the other hand, produced 4.92 larvae per plant compared to 4.92 larvae per plant in the untreated control.
After the third spray, the overall performance of the various treatments revealed that the H. indica treatment at 4,00,000 IJs/cm2 was consistently most effective and superior to the other treatments, with the lowest larval population (1.17 larvae/plant) compared to 4.48 larvae/plant in the untreated control. The next most effective treatment was H. indica at a concentration of 2,00,000 IJs/cm2 (1.34 larvae/plant). Significant differences between the treatments were not identified, with S. feltiae at 2,00,000 IJs/cm2 (1.60 larvae/plant) and S. feltiae at 4,00,000 IJs/cm2 (1.65 larvae/plant) being on par. S. feltiae at 1,00,000 IJs/cm2 (1.83 larvae/plant) and H. indica at 2,00,000 IJs/cm2 (2.25 larvae/plant) treatments were shown to be somewhat efficient in lowering the surviving T. absoluta population. After three sprayings, the overall results of the current experiment demonstrated that among the entomopathogenic agents, H. indica at 2,00,000 IJs/cm2 was consistently effective against T. absoluta, with the lowest larvae population (1.64 Larvae/plant). H. indica at 4,00,000 IJs/cm2 and S. feltiae at 1,00,000 IJs/cm2, as well as S. feltiae at 2,00,000 IJs/cm2, produced greater results against T. absoluta.
Table 4.
Efficacy of entomopathogenic nematode against Tuta absoluta in tomato crop (overall effect of three sprays).
Sr. No
|
Treatments
|
Dose IJs/m2
|
Pre count
|
1st Spray
|
Mean
|
2nd Spray
|
Mean
|
3rd Spray
|
Mean
|
Mean survival population of Tuta absoluta larvae/plant
|
Mean survival population of Tuta absoluta larvae/plant
|
Mean survival population of Tuta absoluta larvae/plant
|
3 DAS
|
7 DAS
|
10 DAS
|
14 DAS
|
3 DAS
|
7 DAS
|
10 DAS
|
14 DAS
|
3 DAS
|
7 DAS
|
10 DAS
|
14 DAS
|
1
|
S. feltiae
|
1,00,000
|
5.77
|
2.417
|
2.16
|
1.72
|
1.59
|
1.97
|
2.15
|
1.92
|
1.79
|
1.51
|
1.84
|
2.66
|
1.70
|
1.63
|
1.34
|
1.83
|
|
|
|
(2.60)*
|
(1.84)
|
(1.77)
|
(1.64)
|
(1.60)
|
(1.71)
|
(1.77)
|
(1.70)
|
(1.67)
|
(1.58)
|
(1.68)
|
(1.91)
|
(1.64)
|
(1.62)
|
(1.53)
|
(1.67)
|
2
|
S. feltiae
|
2,00,000
|
6.52
|
2.677
|
2.36
|
2.05
|
1.68
|
2.19
|
2.12
|
2.10
|
1.80
|
1.38
|
1.85
|
1.83
|
1.76
|
1.64
|
1.17
|
1.60
|
|
|
|
(2.74)
|
(1.91)
|
(1.83)
|
(1.74)
|
(1.63)
|
(1.77)
|
(1.76)
|
(1.76)
|
(1.67)
|
(1.54)
|
(1.68)
|
(1.68)
|
(1.66)
|
(1.62)
|
(1.47)
|
(1.60)
|
3
|
S. feltiae
|
4,00,000
|
6.90
|
2.74
|
2.40
|
2.34
|
2.07
|
2.38
|
2.17
|
2.12
|
2.12
|
1.83
|
2.06
|
1.58
|
1.74
|
1.77
|
1.53
|
1.65
|
|
|
|
(2.80)
|
(1.93)
|
(1.84)
|
(1.82)
|
(1.75)
|
(1.83)
|
(1.78)
|
(1.76)
|
(1.76)
|
(1.68)
|
(1.74)
|
(1.60)
|
(1.65)
|
(1.66)
|
(1.59)
|
(1.62)
|
4
|
H. indica
|
1,00,000
|
7.20
|
2.317
|
2.06
|
1.44
|
1.31
|
1.78
|
1.87
|
1.56
|
1.77
|
1.45
|
1.66
|
2.59
|
2.31
|
2.12
|
1.98
|
2.25
|
|
|
|
(2.85)
|
(1.82)
|
(1.75)
|
(1.56)
|
(1.51)
|
(1.66)
|
(1.69)
|
(1.60)
|
(1.66)
|
(1.56)
|
(1.62)
|
(1.89)
|
(1.82)
|
(1.76)
|
(1.72)
|
(1.79)
|
5
|
H. indica
|
2,00,000
|
6.51
|
2.577
|
2.19
|
1.84
|
1.42
|
2.00
|
1.74
|
1.81
|
1.68
|
1.18
|
1.60
|
1.64
|
1.43
|
1.23
|
1.09
|
1.34
|
|
|
|
(2.73)
|
(1.89)
|
(1.78)
|
(1.68)
|
(1.55)
|
(1.72)
|
(1.65)
|
(1.67)
|
(1.63)
|
(1.47)
|
(1.60)
|
(1.62)
|
(1.56)
|
(1.49)
|
(1.44)
|
(1.52)
|
6
|
H. indica
|
4,00,000
|
6.21
|
2.64
|
2.26
|
2.14
|
2.13
|
2.29
|
1.74
|
1.83
|
2.05
|
1.48
|
1.77
|
1.41
|
1.17
|
1.08
|
1.02
|
1.17
|
|
|
|
(2.68)
|
(1.90)
|
(1.80)
|
(1.77)
|
(1.76)
|
(1.80)
|
(1.65)
|
(1.68)
|
(1.74)
|
(1.57)
|
(1.66)
|
(1.55)
|
(1.42)
|
(1.44)
|
(1.42)
|
(1.45)
|
7
|
Control
|
Water Spray
|
7.36
|
3.53
|
3.87
|
4.08
|
4.09
|
3.89
|
3.79
|
4.03
|
4.28
|
4.24
|
4.08
|
4.16
|
4.23
|
4.61
|
4.92
|
4.48
|
|
|
(2.88)
|
(2.12)
|
(2.20)
|
(2.25)
|
(2.25)
|
(2.20)
|
(2.19)
|
(2.24)
|
(2.29)
|
(2.28)
|
(2.25)
|
(2.27)
|
(2.28)
|
(2.37)
|
(2.43)
|
(2.33)
|
|
SE±
|
N/A
|
0.02
|
0.01
|
0.04
|
0.05
|
|
0.007
|
0.01
|
0.01
|
0.01
|
|
0.02
|
0.02
|
0.02
|
0.01
|
|
|
CD at 5%
|
0.08
|
0.06
|
0.05
|
0.14
|
0.16
|
0.02
|
0.05
|
0.05
|
0.05
|
0.07
|
0.07
|
0.06
|
0.05
|
|
DAS = Days after spray
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
*Figures in parentheses are transformed values Öx+ 0.5
|
|
|
|
|
|
|
|
|
|
|
|
|
Table 5.
Efficacy of entomopathogenic nematode against Tuta absoluta in tomato crop (overall effect of three sprays).
Sr. No
|
Treatments
|
Dose
(IJs/m2)
|
Pre count
|
First spray mean
|
Second spray mean
|
Third spray mean
|
Overall mean
|
1
|
S. feltiae
|
1,00,000
|
5.77
|
1.97
|
1.84
|
1.83
|
1.88
|
|
|
|
(2.60) *
|
(1.71)
|
(1.68)
|
(1.67)
|
(1.68)
|
2
|
S. feltiae
|
2,00,000
|
6.52
|
2.19
|
1.85
|
1.60
|
1.88
|
|
|
|
(2.74)
|
(1.77)
|
(1.68)
|
(1.60)
|
(1.68)
|
3
|
S. feltiae
|
4,00,000
|
6.90
|
2.38
|
2.06
|
1.65
|
2.03
|
|
|
|
(2.80)
|
(1.83)
|
(1.74)
|
(1.62)
|
(1.73)
|
4
|
H. indica
|
1,00,000
|
7.20
|
1.78
|
1.66
|
2.25
|
1.89
|
|
|
|
(2.85)
|
(1.66)
|
(1.62)
|
(1.79)
|
(1.69)
|
5
|
H. indica
|
2,00,000
|
6.51
|
2.00
|
1.60
|
1.34
|
1.64
|
|
|
|
(2.73)
|
(1.72)
|
(1.60)
|
(1.52)
|
(1.61)
|
6
|
H. indica
|
4,00,000
|
6.21
|
2.29
|
1.77
|
1.17
|
1.74
|
|
|
|
(2.68)
|
(1.80)
|
(1.66)
|
(1.45)
|
(1.63)
|
7
|
Control
|
Water Spray
|
7.36
|
3.89
|
4.08
|
4.48
|
4.15
|
|
|
|
(2.88)
|
(2.20)
|
(2.25)
|
(2.33)
|
(2.26)
|
|
SE±
|
|
N/A
|
0.03
|
0.02
|
0.03
|
0.05
|
|
CD at 5%
|
0.08
|
0.11
|
0.08
|
0.11
|
0.16
|
|
DAS = Days after spray
|
|
|
|
|
|
*Figures in parentheses are transformed values Öx+ 0.5
|
|