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Toxicity of four different insecticides against Trilocha varians (Bombycidae: Lepidoptera)
⁎Corresponding author. naeem.iqbal@mnsuam.edu.pk (Naeem Iqbal)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
Ficus benjamina is an important ornamental plant in many countries of the world. Recently, this plant is attacked by a lepidopteran insect pest known as Trilocha varians (Bombucidae: Lepidoptera) in Pakistan. This pest eats the leaves making the plant unaesthetic. In the current study, toxicity of four insecticides (deltamethrin, chlorantraniliprole, fipronil and emamectin benzoate) was evaluated against T. varians. Different concentrations of these insecticides were prepared in distilled water and 3rd instar larvae were exposed using leaf dip bioassay method. The results showed that deltamethrin was more toxic to T. varians followed by emamectin benzoate, fipronil, and chlorantraniliprole. The LC50 of deltamethrin after 12, 24, 36, 48, and 60 h were 18.04, 16.67, 5.74, 2.46, and 1.79 ppm respectively. The results will be useful for management of T. varians.
Keywords
Chlorantraniliprole
Deltamethrin
Fipronil
Ficus
Ornamental plant
1 Introduction
Ficus benjamina L. is an important ornamental plant of family Moraceae and is commonly known as weeping fig. It is native to tropical and sub-tropical countries and is planted along roadsides and in lawns (Zolotuhin & Witt, 2009). Some parts of this plant have anti-fungal and anti-tumor properties, and are also used for making cloth and shelter for human being (Lansky et al., 2008; Sirisha et al., 2010). In some countries, these ficus plants are treated as sacred in various religious believes (Lansky and Paavilainen, 2010).
Several insect pests such as whitefly and mealybug attack on the F. benjamina (Avery et al., 2011). Leaf eating caterpillar, Trilocha varians (Bombucidae: Lepidoptera) is one of the major pest of Ficus spp. in many countries including Nepal, India, Thailand, Taiwan, Java, Malyisha, Southern China, Japan, Philippines and Indonesia (Zolotuhin and Witt, 2009; Chuenban et al. 2017). It is also an economic pest of jackfruit and many other Ficus spp. The major hosts of T. varians are F. religiosa, F. infectoria, F. elastica and F. benghalensis (Kedar et al., 2014).
Recently, this pest has been found to attack F. benjamina in Pakistan (Ramzan et al., 2019). Some plants were severely infested by T. varians larvae causing up to 100% defoliation and death of the plants. Insecticides can play an important role to save this plant from attack of T. varians. Previously some scientists have tested fipronil and malathion to manage this pest in Malaysia (Basari et al. 2019) but such studies are lacking in Pakistan and needs evaluation of some other insecticides too. By keeping in view the importance of this pest, toxicity of different insecticides was evaluated under laboratory conditions. The aim was to find a suitable insecticide for the control of T. varians. This was the first study regarding to control of present pest in Pakistan.
2 Materials and methods
2.1 Collection and rearing of Trilocha varians
The larvae of T. varians were collected from the unsprayed F. benjamina plants at MNS-University of Agriculture Multan. The collected larvae were brought to rearing laboratory of Institute of Plant Protection by following the methodology of Basari et al. (2019) with some modification. Briefly, they were placed in plastic jars containing fresh F. benjamina leaves and reared at 26 ± 2 °C temperature, 50–60% relative humidity (RH) and 14/10 h day-night photoperiod. The larvae were given fresh and tender leaves of F. benjamina on daily basis. The full grown larvae were shifted into new plastic jars for pupation. After emergence from pupae, adults (male and female) were released in pairs into separate plastic jars covered with muslin cloth for egg laying on fresh leaves. The eggs were shifted into separate plastic containers for hatching. All this culture was maintained till five generations.
2.2 Insecticides
Four insecticides, chlorantraniliprole (Coragen 20SC, FMC, Pakistan), deltamethrin (2.5% EC, Jaffer Agrochemicals), emamectin benzoate (Proclaim 019 EC, Syngenta Pakistan) and fipronil (Regent 5% SC, Bayer CropScience) were purchased from the market for bioassay studies against T. varians.
2.3 Bioassay and lethal concentration and time estimation
Toxicity of insecticides was tested against 3rd instar larvae of T. varians. Five concentrations of each insecticide (causing >0% and <100% mortality) were prepared in distilled water. The bioassays were conducted using leaf dip method. The fresh and equal size F. benjamina plant leaves were collected from unsprayed plants grown in the yard of University. Leaves were washed in flowing water and placed in laminar flow for 1–2 h for water evaporation before treatment. Ten leaves were then dipped into a specific concentration for 30 s and then placed at tissue paper for 1 h. After one hours of drying two treated leaves were placed into each glass petri-dish (6 cm diameter) by using forceps. Five larvae were shifted to each per petri-dish with the help of camel hair brush. The petri-dishes were covered with lid to avoid larvae escape. Each concentration was replicated five times. Equal number of petridishes contained untreated leaves served as control. All petridishes were placed in the laboratory under controlled temperature (26 ± 2 °C) relative humidity (50–60%) and photoperiod (14/10 h day-night). The data of mortality was recorded after 12, 36, 48, 60 and 72 h of application.
2.4 Data analysis
The mortality data were corrected using Abbott’s formula (Abbott, 1925), if the mortality rate in the control was more than 5%. The lethal concentrations (LC50 and LC90) of insecticides were calculated through probit analysis using SPSS software ((IBM SPSS Statistics for Windows, Version 23.0, IBM Corp, Armonk, NY, USA).
3 Results
3.1 Lethal concentration estimation
The toxicity of four insecticides against third larval instars of T. varians after 12, 24, 36, 48, 60 and 72 h is shown in Table 1. Deltamethrin was more toxic insecticide followed by emamectin benzoate, fipronil and chlorantraniliprole. The LC50 values of deltamethrin after 12, 24, 36, 48 and 60 h were 18.04, 16.67,5.74, 2.46 and 1.79 ppm, respectively. The LC90 values of deltamethrin after 12, 24, 36, 48 and 60 h were 227.76, 201.44, 150.36, 99.38 and 26.19 ppm, respectively. All exposed larvae were dead after 72 h at almost all of the concentrations of deltamethrin.
Insecticide
Time
(hour)LC50a (ppm) (95% FLb)*
LC90c (ppm) (95% FLb)*
df
χ2d
P
Ne
Chlorantraniliprole
12
84.30(51.89-235.87)
770.50(262.85-13775.56)
3
0.22
0.97
25
Deltamethrin
12
18.04(12.52-28.62)
227.76(63.26-598.97)
3
3.09
0.37
25
Emamectin benzoate
12
47.61(33.32-79.92)
845.36(177.92-4205803.58)
3
0.20
0.97
25
Fipronil
12
66.57(35.72-381.46)
911.32(145.93-1953.26)
3
0.95
0.81
25
Chlorantraniliprole
24
51.68(46.32-85.72)
754.35(197.87-4313401.43)
3
0.90
0.77
25
Deltamethrin
24
16.67(14.34-34.61)
201.44(98.85-1033.29)
3
0.24
0.97
25
Emamectin benzoate
24
20.61(9.01-39.02)
533.86(154.21-57114.25)
3
0.28
0.96
25
Fipronil
24
36.60(16.37-103.59)
721.74(183.65-64282.84)
3
0.87
0.83
25
Chlorantraniliprole
36
21.43(9.85-31.34)
509.03(199.99-1579.78)
3
2.16
0.98
25
Deltamethrin
36
5.74(0.44-11.75)
150.36(60.58-6011.57)
3
1.29
0.73
25
Emamectin benzoate
36
17.53(4.45-36.72)
307.09(149.89-1449.73)
3
0.57
0.90
25
Fipronil
36
21.99(13.36-52.25)
605.73(141.61-120706.82)
3
0.24
0.97
25
Chlorantraniliprole
48
19.87(4.78-40.63)
221.14(98.44-3443.15)
3
0.65
0.81
25
Deltamethrin
48
2.46(.002-7.23)
99.38(40.73-19950.68)
3
0.28
0.96
25
Emamectin benzoate
48
14.45(6.45-23.48)
213.18(90.56-2437.15)
3
1.39
0.71
25
Fipronil
48
19.10(9.32-83.16)
352.17(106.72-14372.21)
3
0.44
0.93
25
Chlorantraniliprole
60
14.87(7.32-23.45)
160.63(77.95-1368.58)
3
7.34
0.95
25
Deltamethrin
60
1.79(.008-5.06)
26.19(13.979-122.82)
3
1.29
0.73
25
Emamectin benzoate
60
12.93(5.92-20.38)
155.76(73.57-1138.93)
3
5.25
0.15
25
Fipronil
60
6.03(2.64-9.52)
70.45(34.38-458.59)
3
1.39
0.71
25
Chlorantraniliprole
72
9.87(5.45-8.88)
26.98(19.98-51.34)
3
0.31
0.99
25
Deltamethrin
72
-
-
-
-
-
-
Emamectin benzoate
72
5.84(2.65-8.55)
23.75(16.73-45.91)
3
0.40
0.94
25
Fipronil
72
4.64(1.74-7.49)
51.22(26.83-265.61)
3
0.30
0.96
25
The LC50 values of emamectin benzoate and chlorantraniliprole after 12 h were 47.61 and 84.30 ppm while after 72 h, they were 5.84 and 9.87 ppm respectively (Table 1). Emamectin benzoate was found to be more toxic than fipronil and chlorantraniliprole. However, LC50 and LC90 values of fipronil after 12, 24, 36, 48, 60 and 72 h were 66.57, 36.60, 21.99, 19.10, 6.03, 4.64 and 911.32, 721.74, 605.73, 352.17, 70.45, 51.22 ppm, respectively (Table 1).
4 Discussion
The various methods such as cultural, physical, botanical, biological and chemical have been practiced at national and international level to control the pest population in different countries (Udayagiri, 1988; Kedar et al., 2014). Among all these methods, chemical method is the most effective and widely used to control insect pests. If proper concentration of an insecticide is applied, it can kill the insect pest within shorter period of time. The use or exposure of similar groups of insecticides for long time can cause insecticide resistance in insect pests. It is advised to use different insecticides in rotation to manage the pest population.
Current study was conducted to test the efficacy of different insecticides to control the pest population under laboratory conditions. For this purpose, four insecticides, chlorantraniliprole, deltamethrin, emamectin benzoate and fipronil were chosen to test the LC50 and LC90 against the larvae of T. varians. There are limited studies conducted against this pest that involve testing different insecticides. In Malaysia a study has been conducted to determine the lethal time 50 (LT50) and lethal time 90 (LT90) by using two insecticides, fipronil and malathion. However, studies using newer chemicals had not been conducted before to determine the LC50 and LC90 against this pest in the world including Pakistan. Thus, we intended to calculate LC50 and LC90 of four insecticides by using different concentrations against this pest.
Our study showed that all insecticides were proved toxic and effective to T. varians. Among all insecticides, deltamethrin was proved most toxic insecticide and caused high mortality of larvae as compared to other insecticides partularly chlorantraniliprole which caused least mortality. While authors in Malaysia (Basari et al., 2019) have reported that fipronil was most toxic insecticides than malathion. Our findings are not in line with the findings of their previous study (Basari et al., 2019). In other studies, fipronil has been reported very toxic insecticides with lower LT50 and LT50 values against other insect pests (Colliot et al., 1992; Zhang et al., 2015). which was not the case in our study against T. varians. Fipronil was slow acting insecticide in our study and similar observations have reported by earlier researchers against various insect pests (Gautam et al., 2012; Li et al., 2016). During the study no mortality was recorded under control and all larvae change into pupae and than emerged as adults after few (six) days. Overall, the present study reported that deltamethrin could be better option to control this the emerging insect pests (T. varians).
5 Conclusion
The current study revealed that deltamethrin and emamectin benzoate were more lethal and toxic to larvae of T. varians. Hence these two insecticides can be used for the management of T. varians.
Acknowledgements
We are all highly thankful to Muhammad Nawaz Shareef University of Agriculture Multan for providing facility to perform the current research work. Authors would like to acknowledge the support of the King Khalid University through RCAMS/KKU/010-19 under the Research Center for Advanced Materials Science (RCAMS) at King Khalid University, Kingdom of Saudi Arabia.
Conflict of interest
Authors have no conflict of interest.
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