3.1 Insect densities on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season 2021 and early season, 2022
In the late season 2021, population densities of Aulacophora foveicollis, Aulacophora nigripennis, Aulacophora hilaris, Coridus viduatus and Epilachna chrysomelina were significantly (p < 0.05) lower in the plots sprayed at 8.00, 6.00, 4.00 and 2.00 kg/ha once a-week while the untreated plot had lower densities of these insect pests. The density of A. foveicollis, A. hilaris, and E. chrysomelina were significantly higher in the control plots (11.00), (11.33) and (14.00), while the lowest was observed in the plots sprayed at 8.00, 6.00, 4.00 and 2.00 kg/ha once a-week in the early season, 2022 (Table 1).
Table 1
Insect densities on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season 2021 and early season, 2022
Frequency
|
Rate (kg/ha)
|
Aulacophora foveicollis
|
Aulacophora nigripennis
|
Aulacophora hilaris
|
Bactrocera cucurbitae
|
Coridius viduatus
|
Epilachna chrysomelina
|
Late season, 2021
|
|
|
|
|
|
|
|
Once
|
8.00
|
1.33f
|
1.00g
|
0.33e
|
0.33c
|
1.67d
|
2.10f
|
a-week
|
6.00
|
2.00f
|
1.67g
|
1.00e
|
0.67bc
|
3.33d
|
3.02f
|
|
4.00
|
1.33f
|
1.33g
|
0.67e
|
1.00bc
|
1.67d
|
2.33f
|
|
2.00
|
1.67f
|
1.67g
|
1.00e
|
0.67bc
|
2.33d
|
3.40f
|
Once-in
|
8.00
|
3.67e
|
3.67f
|
3.00d
|
2.00bc
|
7.33c
|
7.30de
|
Two-weeks
|
6.00
|
6.33b-d
|
4.67ef
|
4.33cd
|
2.67a-c
|
8.00bc
|
6.00e
|
|
4.00
|
5.33cd
|
5.67c-e
|
4.33cd
|
2.67a-c
|
10.33b
|
6.02e
|
|
2.00
|
7.33b
|
5.33de
|
6.33b
|
3.00a-c
|
10.33b
|
8.67c
|
Once-in
|
8.00
|
5.33d
|
4.33ef
|
3.33d
|
2.67a-c
|
8.00bc
|
8.03cd
|
Three-weeks
|
6.00
|
7.33b
|
6.33b-d
|
4.67cd
|
1.33bc
|
9.33bc
|
7.40de
|
|
4.00
|
6.67bc
|
7.00bc
|
5.67bc
|
3.00a-c
|
9.33bc
|
8.33cd
|
|
2.00
|
7.33b
|
7.33b
|
7.00b
|
3.67ab
|
9.00bc
|
10.33b
|
Control
|
0
|
10.00a
|
9.67a
|
10.33a
|
5.00a
|
12.00a
|
13.10a
|
Early Season, 2022
|
|
|
|
|
|
Once
|
8.00
|
2.33f
|
2.00a-c
|
1.33e
|
1.33c
|
2.67h
|
3.00f
|
a-week
|
6.00
|
3.00f
|
2.67a-c
|
2.00e
|
1.67bc
|
4.33g
|
4.00f
|
|
4.00
|
2.33f
|
2.33a
|
1.67e
|
2.00bc
|
2.67h
|
3.33f
|
|
2.00
|
2.67f
|
2.67a-c
|
2.00e
|
1.67bc
|
2.67h
|
4.00f
|
Once-in
|
8.00
|
4.67e
|
4.67a-c
|
4.00d
|
3.00bc
|
8.33cd
|
8.00de
|
Two-weeks
|
6.00
|
7.33b-d
|
5.67a-c
|
5.33cd
|
3.67a-c
|
9.00bc
|
7.00e
|
|
4.00
|
6.33cd
|
9.67b
|
5.33cd
|
3.67a-c
|
6.33df
|
7.00e
|
|
2.00
|
8.33b
|
6.33a-c
|
7.33b
|
4.00a-c
|
8.33cd
|
9.67c
|
Once-in
|
8.00
|
6.33cd
|
5.33a-c
|
4.33d
|
3.67a-c
|
9.00bc
|
9.00cd
|
Three-weeks
|
6.00
|
8.33b
|
7.33a-c
|
5.67cd
|
2.33bc
|
10.33ab
|
8.00d-e
|
|
4.00
|
7.67bc
|
7.33a-c
|
6.67bc
|
4.00a-c
|
7.67c-f
|
9.33cd
|
|
2.00
|
8.33b
|
8.33a-c
|
8.00b
|
4.67ab
|
8.33b-e
|
11.33b
|
Control
|
0
|
11.00a
|
10.67a
|
11.33a
|
6.00a
|
11.00a
|
14.0a
|
Mean values along the same column within a season followed by the similar alphabets are not significantly different from one another at another using SNK at p < 0.05.
3.2 Characteristics of insect-induced damage on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season, 2021
In the late season 2021, percent leaf damage, percent leaf damage intensity, percent flower abortion, percent fruit damage and percent relative yield loss were significantly influenced by rate and application frequency of B. bassiana. Percent leaf damage and percent leaf damage intensity were similar across treated plots while the control plots had the highest (60.46% and 60.17%) percent leaf damage and percent leaf damage intensity. Also, the percent fruit damage was significantly lower (P < 0.05) in the plots sprayed at 8.00, 6.00, 4.00 and 2.00 kg/ha once a-week while control plot observed the highest percent fruit damage (Table 2).
Similarl to the late season 2021, percent leaf damage was not significantly different across treated plots with the control plot having the highest percent leaf damage. Also, percent relative yield loss was significantly lower in the plots sprayed at 8.00, 6.00, 4.00 and 2.00 kg/ha once a-week, while the control plot had the highest percent relative yield loss (Table 3).
3.3 Yield of cucumber at different application rates and frequencies of Beauveria bassiana in late season, 2021 and early season, 2022
Cucumber fruits yield was significantly influenced by rate and application frequency of B. bassiana in the late season 2021. Plots sprayed at 8.00 kg/ha produced higher weight of cucumber fruits relative to other plots. The lowest yield was however observed in the control plots.
Also, percent yield increase was significantly higher in the plots sprayed at 8.00 kg/ha relative to the other treated plots in the early season, 2022 (Table 4).
Table 2
Characteristics of insect-induced damage on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season, 2021
Frequency
|
Rate (kg/ha)
|
Rate (%)
|
Leaf Damage (%)
|
Leaf
Damage intensity (%)
|
Flower Abortion (%)
|
Fruit Damage (%)
|
Relative yield loss (%)
|
Once
|
8.00
|
100
|
6.75b
|
23.67b
|
12.28d
|
13.57f
|
14.16d
|
a-week
|
6.00
|
75
|
9.57b
|
27.44b
|
13.75d
|
14.17f
|
12.94d
|
|
4.00
|
50
|
10.44b
|
25.32b
|
14.93cd
|
15.90f
|
12.63d
|
|
2.00
|
25
|
13.23b
|
24.94b
|
15.95cd
|
14.93f
|
15.58cd
|
Once-in
|
8.00
|
100
|
16.55b
|
32.43b
|
20.66b-d
|
30.27de
|
32.86bc
|
Two-weeks
|
6.00
|
75
|
16.95b
|
31.79b
|
29.62b-d
|
26.00e
|
32.95ab
|
|
4.00
|
50
|
16.95b
|
32.31b
|
24.43b-d
|
28.70de
|
31.51bc
|
|
2.00
|
25
|
18.51b
|
34.60b
|
40.09ab
|
40.00c
|
46.37ab
|
Once-in
|
8.00
|
100
|
22.05b
|
35.76b
|
32.86b-d
|
44.17c
|
41.94ab
|
Three-weeks
|
6.00
|
75
|
24.49b
|
34.03b
|
39.12ab
|
37.03cd
|
38.03ab
|
|
4.00
|
50
|
25.09b
|
39.79b
|
36.14b-d
|
31.93de
|
43.55ab
|
|
2.00
|
25
|
23.81b
|
38.17b
|
40.35a-c
|
54.30b
|
48.33ab
|
Control
|
0
|
0
|
60.46a
|
60.17a
|
60.17a
|
62.70a
|
72.72a
|
Mean values along the column followed by the same alphabets are not significantly different from one another using SNK at p < 0.05.
Table 3
Characteristics of insect-induced damage on cucumber treated with Beauveria bassiana at different application rates and frequencies in the early season, 2022
Frequency
|
Rate (kg/ha)
|
Leaf Damage (%)
|
Leaf
Damage Intensity (%)
|
Flower Abortion
(%)
|
Fruit Damage (%)
|
Relative yield loss (%)
|
Once
|
8.00
|
17.44b
|
11.88e
|
13.94d
|
9.87d
|
12.25e
|
a-week
|
6.00
|
21.77b
|
16.97de
|
16.37d
|
14.00cd
|
15.79e
|
|
4.00
|
19.91b
|
17.88de
|
16.91cd
|
16.50cd
|
15.12e
|
|
2.00
|
19.09b
|
22.57de
|
18.33cd
|
25.47b-d
|
25.68de
|
Once-in
|
8.00
|
24.10b
|
29.73cd
|
23.37b-d
|
34.70a-d
|
39.34b-d
|
Two-weeks
|
6.00
|
26.52b
|
20.33de
|
32.40b-d
|
34.33a-d
|
37.98ab
|
|
4.00
|
26.80b
|
29.44cd
|
25.86b-d
|
35.70a-d
|
35.01cd
|
|
2.00
|
30.40b
|
28.70cd
|
39.50ab
|
43.90a-c
|
55.10ab
|
Once-in
|
8.00
|
31.05b
|
37.13bc
|
34.60b-d
|
40.00a-c
|
51.85a-c
|
Three-weeks
|
6.00
|
29.46b
|
42.10b
|
39.73a-d
|
47.73ab
|
45.16a-c
|
|
4.00
|
36.01b
|
48.31b
|
37.61b-d
|
42.40a-c
|
52.83a-c
|
|
2.00
|
33.94b
|
44.02b
|
43.18a-c
|
54.53ab
|
59.62ab
|
Control
|
0
|
47.64a
|
80.64a
|
61.36a
|
61.97a
|
72.51a
|
Mean values along the column followed by the same alphabets are not significantly different from one another using SNK at p < 0.05.
Table 4
Yield of cucumber at different application rates and frequencies of Beauveria bassiana in late season, 2021 and early season, 2022
Late season, 2021
|
Early season, 2022
|
Frequency
|
Rate (kg/ha)
|
Yield/plant(kg)
|
Yield/ha(ton)
|
Yield increase (%)
|
|
Yield/plant (kg)
|
Yield/ha(ton)
|
Yield increase (%)
|
Once
|
8.00
|
0.97a
|
14.43a
|
546.67a
|
|
0.86a
|
13.44a
|
514.29a
|
a-Week
|
6.00
|
0.74c
|
13.57ab
|
393.33c
|
|
0.64c
|
12.06b
|
357.14c
|
|
4.00
|
0.83b
|
13.50ab
|
453.33b
|
|
0.73b
|
11.22bc
|
421.43b
|
|
2.00
|
0.65d
|
12.23b
|
333.33d
|
|
0.55d
|
10.48c
|
292.86d
|
Once- in
|
8.00
|
0.47ef
|
7.12de
|
213.33ef
|
|
0.37ef
|
6.24e
|
164.29ef
|
Two-weeks
|
6.00
|
0.59d
|
8.88c
|
293.33d
|
|
0.49d
|
8.20d
|
250.00d
|
|
4.00
|
0.50e
|
7.51cd
|
233.33e
|
|
0.39e
|
6.686e
|
164.29e
|
|
2.00
|
0.37gh
|
5.60ef
|
146.67gh
|
|
0.27gh
|
4.44fg
|
92.86gh
|
Once-in
|
8.00
|
0.36f-h
|
5.45ef
|
140.00f-h
|
|
0.26f-h
|
4.38fg
|
85.71f-h
|
Three-weeks
|
6.00
|
0.44e-g
|
6.57d-f
|
193.33e-g
|
|
0.34e-g
|
5.64ef
|
142.86e-g
|
|
4.00
|
0.35f-h
|
5.31ef
|
133.33f-h
|
|
0.25gh
|
4.23fg
|
78.57gh
|
|
2.00
|
0.31h
|
4.63f
|
106.67h
|
|
0.21hi
|
3.47gh
|
50.00hi
|
Control
|
0
|
0.15i
|
2.26g
|
-
|
|
0.14i
|
2.34h
|
-
|
Mean values along the column followed by the same alphabets are not significantly different from one another using SNK at p < 0.05.
Table 5
Correlation coefficients of the relationship between insect pest densities, fruit damage and cucumber yield in the late season, 2021 and early season, 2022.
|
Late season 2021
|
|
Early season, 2022
|
Insect
|
Leaf damage (%)
|
Yield/ha
|
Fruit damage (%)
|
|
Leaf damage (%)
|
Yield/ha
|
Fruit damage (%)
|
Aulacophora foveicollis
|
0.62**
|
-0.89**
|
0.86**
|
|
0.76**
|
-0.87**
|
0.82**
|
Aulacophora hilaris
|
0.71**
|
-0.87**
|
0.86**
|
|
0.79**
|
-0.88**
|
0.79**
|
Aulacophora nigripennis
|
0.67**
|
-0.90**
|
0.85**
|
|
0.44
|
-0.45**
|
0.41
|
Epilachna chrysomelina
|
0.71**
|
-0.9**
|
0.94**
|
|
0.81**
|
-0.95**
|
0.82**
|
Coridius viduatus
|
0.57**
|
− 0.92**
|
0.79**
|
|
0.66**
|
-0.87**
|
0.73**
|
Bactrocera cucurbitae
|
NA
|
NA
|
0.72**
|
|
NA
|
NA
|
0.48*
|
** = significant at p < 0.01 |
NA = not applicable |
Table 6
Profitability*of Beauveria bassiana application at different rates and frequencies in late season, 2021 and early season, 2022
Late season, 2021
|
|
Early season, 2022
|
Frequency
|
Rate (kg/ha)
|
Number of spray
|
Additional Revenue($)
|
Additional Cost ($)
|
Marginal Return
|
|
Additional Revenue($)
|
Additional Cost ($)
|
Marginal Return
|
Once
|
8.00
|
6
|
6,582.19
|
3,430.10
|
1.00
|
|
7,204.18
|
3,430.10
|
1.00
|
a-week
|
6.00
|
6
|
6,117.06
|
3,389.00
|
0.80
|
|
6,308.52
|
3,389.00
|
0.86
|
|
4.00
|
6
|
6,079.20
|
3,245.67
|
0.87
|
|
5,763.34
|
3,245.67
|
0.78
|
|
2.00
|
6
|
5,392.31
|
3,090.98
|
0.74
|
|
5,283.06
|
3,090.98
|
0.71
|
Once-in
|
8.00
|
3
|
2,628.55
|
1,768.59
|
0.49
|
|
2,531.20
|
1,768.59
|
0.43
|
Two-weeks
|
6.00
|
3
|
3,580.45
|
1,748.31
|
1.05
|
|
3,808.28
|
1,748.31
|
1.18
|
|
4.00
|
3
|
2,839.48
|
1,728.03
|
0.64
|
|
2,816.77
|
1,728.03
|
0.63
|
|
2.00
|
3
|
1,806.45
|
1,707.75
|
0.05
|
|
1,362.95
|
1,707.75
|
-0.20
|
Once-in
|
8.00
|
2
|
1,725.32
|
1,541.43
|
0.12
|
|
1,324.01
|
1,541.43
|
-0.14
|
Three weeks
|
6.00
|
2
|
2,331.08
|
1,511.69
|
0.54
|
|
2,141.78
|
1,511.69
|
0.42
|
|
4.00
|
2
|
1,649.61
|
1,476.53
|
0.12
|
|
1,226.67
|
1,476.53
|
-0.17
|
|
2.00
|
2
|
1,281.82
|
1,324.55
|
-0.03
|
|
733.40
|
1,324.55
|
-0.45
|
Control
|
0
|
-
|
-
|
-
|
|
|
-
|
-
|
-
|
Based on 250.00 and 300.00 per kg in late season, 2021 and early season, 2022. Also, Conversion rate to dollar () is 462.232
3.4 Correlation coefficients of the relationship between insect pest densities, fruit damage and cucumber yield in 2021 and 2022
In both seasons, as the population densities of leaf and stem insect pests: A. indica, A. hilaris, A. nigripennis, A. foveicollis, A. vittatum, E. chrysomelina and C. viduatus increases, the percent leaf damage also increases. Also, as the population density of B. cucurbitae (fruits insect pests) increases percent fruit damage also increases (Table 6).
3.5 Profitability of Beauveria bassiana at different rates and frequencies in early season, 2021 and 2022
Cucumber production was highly profitable in the plots sprayed with B. bassiana at 8.00 kg/ha once a-week and 6.00 kg/ha once-in two-weeks in the late season 2021 and early season, 2022. Furthermore, profitability test showed that plot sprayed at 2.00 kg/ha once in three-weeks was not profitable in the late season 2021. Also, the plots sprayed at 2.00 kg/ha once in two weeks and plots sprayed at 8.00kg/ha, 4.00kg/ha and 2.00 kg/ha once in three-weeks was not profitable in the early season, 2022. (Table 5)