Introduction

Earais vittella (F.) (Noctuidae: Lepidoptera), also known as spotted bollworm, is a notorious polyphagous pest of many malvaceous crops (Aziz et al. 2012). Some of its major host crops include Gossypium spp. (cotton), Abelmoschus esculentus (okra), Abutilon indicum, Hibiscus cannabinus, Althaearosea (hollyhock) and Malwa parviflora (sonchal) (Rasool et al. 2002; Jan et al. 2015; Rahman et al. 2016). The spotted bollworm is active throughout the year and have 6 to 8 generations during each year. Several buds and bolls are damaged by a single larva in its life span. In cotton, it pupates in bolls and reduces the boll growth (Aziz et al. 2011; Jan et al. 2015) commonly the buds, flowers, and fruits are attacked by second instar larvae and results in the reduction of quality and quantity. It may reduce the yield up to 50% in cotton and about 69% in okra (Aziz et al. 2011).

The use of chemicals plays a key role in the management of pests in fields, resulting in a low risk of yield loss (Popp and Hantos 2011). E. vitella infestation has been managed using different insecticides including, pyrethroids and organophosphates (Praveen et al. 2007; Umrao et al. 2013). Irregular and massive application of such chemicals has resulted in resistance development in field pests (Abbas et al. 2014; Gulzar and Wright 2014; Abbas and Shad 2015; Ahmad et al. 2019). Novaluron is one of the recent insect growth regulators (IGR) that belong to the insecticidal group, benzoylphenyl urea. It is a chitin synthesis inhibitor that acts through ingestion and contact. It targets the larval stage of insects which synthesize chitin actively (Lohmeyer and Pound 2012). The residual activity of novaluron in field conditions depends upon the environmental conditions and ranges from 10 to 30 days (Ishaaya et al. 2003). It has a very low toxic effect on mammals, birds, earthworms (Ishaaya et al. 2007) and adults of non-targeted beneficial insect species (Cutler et al. 2005).

The application of pesticides in fields does not kill all the pest populations with immediate effects, so over time the pesticide decreases and, as a result, the sublethal effects including behavioral and physiological changes in pests can occur (Rehan and Freed 2015). These sublethal concentrations of pesticides can significantly alter the adult development, adult insect weight, larval and pupa periods and reproduction parameters of the insect (Han et al. 2012). For a comprehensive pesticide evaluation, only acute toxicity is not enough, but the sublethal effects may also be included (Zhang et al. 2015). Previously, Rahmani and Bandani (2013) found that the sub-lethal doses of thiamethoxam chemical significantly altered the different Hippodamia variegate population parameters in adverse modus. This study was planned to elucidate the sublethal effects of the novaluron on population parameters of E. vittella by application of Age-stage, two-sex life table theory. The finding of this study may be helpful to monitor the insecticide resistance in E. vittella to insect growth regulators (IGRs) in fields and develop improved integrated pest management strategies.

Materials and Methods

Insect culture and insecticides

Laboratory culture of spotted bollworm (E. vittella) was established from the larvae collected from okra fields in the surrounding of Rawalpindi, Taxila and Attock. The infested pods from the fields were transferred into transparent plastic jars (20 cm length and 10 cm wide) and were kept under control conditions (27 ± 2°C, 60 ± 5% R.H. photoperiod of 16 L: 8 D). Insect culture was maintained on okra fruits as described by Al-Mehmmady (2000). Fresh okra fruits were washed thoroughly by tap water and air-dried before feeding to the neonates. The okra fruits were cut into 0.5‒1.0 cm pieces, 4‒5 larvae were released per piece and placed in the plastic container. The food was replaced daily till pupation. The larvae were carefully removed from the okra pods and the excreta were cleaned. The pupae were shifted to another plastic jar (10 cm length and 5 cm width) until adult emergence. The emerged adults were shifted to adult cages and fed with 10% sugar solution. Nappy strips were hanged in the adult cages as oviposition sites, these strips were replaced regularly when eggs were observed.

Novaluron, insect growth regulator, (Corvus®) FMC Pvt. Ltd. was used at the recommended dose along with different concentrations against the 1^st instar larvae of spotted bollworm (E. vittella) to investigate the larvicidal effects.

Bioassays

Bioassays were performed by using diet emersion method and toxicity of novaluron was checked against 1^st larval instar of spotted bollworm (E. vitella). Different concentrations of novaluron by serial dilutions (mg L^-1) of stock solution were prepared using distilled water. Fresh okra fruits were dipped separately in each concentration for 10 sec and then dried for 10 min at room temperature. Five okra fruits were used in one replication. Two 1st instar larvae were released on each okra pods in all replications treated with different concentrations. Each treatment was replicated four times. Distilled water was used as a control treatment. All the treated larvae were kept under controlled conditions (Temperature of 25 ± 2°C; R. H. of 65 ± 5%). Mortality data were assessed after 72 h.

Sublethal effects on demographic parameters of E. vittella

In life table study, 210 eggs were used, which were collected after 24 h of deposition by females of the laboratory population. Three treatments (control, LC₂₀, and LC₅₀) were prepared for this experiment. Seventy eggs were treated with each treatment. Each egg is an individual petri dish that was considered as one replicate (Huang and Chi 2013; Zhang et al. 2015). All the Petri dishes were kept under controlled conditions. The egg hatching data were recorded daily. The neonates from control, LC₂₀ and LC₅₀ were shifted on the okra pods treated with control, LC₂₀ and LC₅₀, respectively. The larval development was observed daily and fresh okra pods were provided after each instar. Pupae were removed and placed in new Petri dishes until emergence. After the adult emergence, they were paired (one male and one female) and transferred to individual plastic containers for oviposition. The adults were checked daily for oviposition and transferred to new containers for egg-laying. The fecundity and survival rate of the adults have assessed until the death of the adults.

Data analysis

The LC values were calculated based on mortality data by using R Statistical Software version 2.9.0 (R Development Core Team 2009). The data regarding different stage development periods, survival rate and fecundity along with oviposition periods were analyzed using Age-stage, two-sex life table theory (Chi and Liu 1985; Chi 1988) with TWO SEX-MS Chart software (Chi 2017). Means of the biological parameters were compared by using 100,000 bootstrap techniques to achieve stable SE estimates (Huang and Chi 2013). The curves for age-specific survival rate, fecundity, life expectancy and reproductive values were generated bu using Sigma Plot 14.0. The net reproductive rate was calculated as:

The intrinsic rate of increase (r) is calculated by using the iterative bisection method from:

With age indexed from zero (Goodman 1982). The mean generation time (T) is calculated as follow:

The Gross reproductive rate (GRR) is calculated by the formula as follow:

The age-specific survival rate (l_x) and age-specific fecundity (m_x) were given as:

Results

Toxicity bioassays

The toxicity of novaluron against the 1^st instar of E. vittella after 72 h is given in Table 1. The LC₂₀and LC₅₀ were calculated as 2.224 mg L^-1 and 9.837 mg L^-1, respectively.

Sub-lethal effects of novaluron on biological parameters of E. vittella

The developmental periods, fecundity and adult longevity of both males and females of E. vittella treated with sub-lethal concentrations (LC₂₀ and LC₅₀) of novaluron are given in Table 2. Egg duration was significantly (P ≤ 0.005, df=2, F=87.61) prolonged when treated with sub-lethal concentrations (4.26 days and 4.07 days for LC₅₀ and LC₂₀ respectively of novaluron as compared with the control (3.66 days). Total larval time was also increased by treating with sub-lethal concentrations (LC₅₀ andLC₂₀) as 12.54 days and11.23 days respectively (P ≤ 0.005, df=2, F=117.24) as compared with control (11.03 days). No significant variation was noted between LC₂₀(11.35 days) and LC₅₀ (11.47 days) in terms of the pupal period but differed significantly (P ≤ 0.005, df=2, F=122.82) when compared with the untreated larvae (Table 2). Adult male longevity was not significantly different (p=0.104, df=2, F=11.82), while female longevity was significantly (P ≤ 0.005, df=2, F=92.87) different ranging from highest (12.7 days) on control to the lowest (7.62 days) on LC₅₀. The differences in total pre-oviposition period (TPOP) between sub-lethal concentrations were statistically non-significant (P ≤ 0.01, df=2, F=7.45), while a significant difference was found between the control and treated larvae. The number of eggs per female varied significantly (P ≤ 0.005, df=2, F=648.22) between sub-lethal concentrations (238.11 and 268.5 eggs per female in LC₅₀ and LC₂₀ respectively). The highest fecundity (330.9 eggs per female) was noted for untreated larvae.

Sub-lethal effects of novaluron on population parameters of E. vittella

Novaluron significantly altered the population parameters of the E. vittella (Table 3). To estimate the population parameters, the bootstrap method with 100,000 replicate sample method was used. The intrinsic rate of increase was decreased by treating with both the concentrations of novaluron (0.128 and 0.140 d^-1 for LC₅₀ and LC₂₀, respectively) as compared with the untreated larvae (0.166 d^-1). A similar trend was found in the finite rate of increase (λ), as the highest value for λ was found in control larvae (1.181 d^-1) which gradually decreases with an increase in concentration from LC₂₀ to LC₅₀ as 1.150 and 1.137 d^-1 respectively. A significant decrease was also observed in net reproductive rate after novaluron treatment from being highest on control larvae (94.542 offsprings per individual) to 76.714 and 61.228 offsprings per individual for LC₂₀ and LC₅₀ treated larvae respectively. Moreover, the gross reproductive rate (GRR) of LC₂₀treated larvae (146.45, offsprings per individual) was significantly similar to that of LC₅₀ and control. The highest GRR was recorded for control larvae (183.42 offsprings per individual), while the lowest recorded for LC₅₀ treated larvae (136.77 offsprings per individual) which were both statistically significant to each other. The mean generation time was prolonged in the treated larvae compared to the control larvae. Minimum mean generation time was taken by the control larvae (27.255 d), followed by LC₂₀ treated larvae (30.967 d). The maximum days were recorded on LC₅₀ treated larvae (31.917 d). The curves of developmental rates of the individuals showed an overlapped nature showing the differences in their development rates (Fig. 1). Females were emerged late in the population than males, while their survival was longer than males. The LC₂₀ and LC₅₀ treatment were observed with less number of larvae as compared with untreated. The longest time for development was noted for LC₅₀and LC₂₀ treated larvae when compared with untreated larvae (Fig. 1).

Age-specific survival rates (lx), age-specific fecundity (fx, female), age-specific fecundity for total population and age-specific maternity (lxmx) are presented in Fig. 2. A significant decline in the curve of lx was noted in LC₂₀ and LC₅₀ treated larvae after 32 days of the treatment. The untreated group has the highest top peaks of fx and mx than compared with the LC₂₀ and LC₅₀ treated group. A significant variation was shown in the life expectancy (e_xj) among the treated (LC₂₀ and LC₅₀) and untreated larvae (Fig. 3). The maximum life expectancy of new eggs was recorded in LC₅₀(39.0 days), followed by LC₂₀ (38.0 days) while the minimum life expectancy of eggs was recorded in the untreated group (36.0 days). Reproductive rate (v_xj) is defined as the measure of dedication to newly coming offspring in the future from age x to stage j (Fig. 4). The contribution of males in the population to the next generation was not well defined, therefore the curve for males was not included. A decline was observed in the reproductive values when larvae treated with LC₅₀ and LC₂₀ as compared to the untreated larvae. Maximum v_xj was recorded on the untreated group, while the minimum was observed in LC₅₀ treated group.

Discussion

In the current study, Age-stage, two-sex life table theory was utilized to calculate the population parameters of E. vittella exposed to the sublethal concentrations of novaluron. Age-stage, two-sex life table study is a promising way to estimate the population parameters of the pest by considering both the Table 1: Acute toxicity of novaluron on the 1^stinstar of E. vittella after 72 h of treatment

Chemical	n	Concentration mg liter^-1 (95% CL)			Slope ± SE	χ² (df)
		LC₁₀	LC₂₀	LC₅₀
Novaluron	240	1.022 (0.534-2.156)	2.224 (1.162-4.256)	9.837 (5.140-18.827)	1.304 ± 0.144	0.997 (5)

LC (lethal concentration), n (number of samples), CL (confidence level), SE (standard error), χ² (Chi square), df (degree of freedom)

Table 2: Life table parameters of E. vittella treated with sub-lethal concentrations of novaluron

Treatment	Control		LC₂₀			LC₅₀
	n	Mean ± SE	n	Mean ± SE	n		Mean ± SE
Egg (days)	70	3.66 ± 0.1^b	70	4.07 ± 0.094^a	70		4.26 ± 0.125^a
1^st instar (days)	64	2.28 ± 0.08^c	60	2.33 ± 0.088^b	58		2.52 ± 0.094^a
2^nd instar (days)	54	2.19 ± 0.076^b	50	2.20 ± 0.082^b	56		2.54 ± 0.096^a
3^rd instar (days)	48	2.17 ± 0.078^b	44	2.36 ± 0.105^a	46		2.48 ± 0.106^a
4^th instar (days)	46	2.13 ± 0.072^b	42	2.19 ± 0.088^b	40		2.53 ± 0.125^a
5^th instar (days)	46	2.26 ± 0.094^b	40	2.15 ± 0.082^b	38		2.47 ± 0.125^a
Larva (days)	46	11.03 ± 0.028^c	40	11.23 ± 0.041^b	38		12.54 ± 0.013^a
Pupa(days)	41	8.74 ± 0.201^b	34	11.35 ± 0.15^a	31		11.47 ± 0.151^a
Male longevity(days)	18	8.52 ± 2.066^a	19	7.72 ± 1.56^a	16		7.12 ± 0.331^a
Female longevity(days)	23	12.7 ± 2.13^a	15	9.04 ± 1.21^b	14		7.62 ± 0.242^c
APOP	23	1.2 ± 0.133^a	15	1.00 ± 0.00^a	14		1.00 ± 0.00^a
TPOP	23	24.5 ± 0.619^b	15	28.3 ± 0.26^a	14		29.22 ± 0.464^a
Fecundity (eggs/f)	23	330.9 ± 26.41^a	15	268.5 ± 19.67^b	14		238.11 ± 14.24^c

LC (lethal concentration), SE (standard error), n (number of insects exposed. Adult pre oviposition period (APOP), total pre oviposition period (TPOP), means sharing similar letters in a row are not different statistical at 5% probability

Table 3: Effect of sub-lethal concentration of novaluron on the biological parameters of E. vittella

Population parameters	Control		LC₂₀		LC₅₀
Population parameters	Mean	SE	Mean	SE	Mean	SE
Intrinsic rate of increase (r)	0.166^a	0.011	0.140^b	0.009	0.128^c	0.010
Finite rate of increase (λ)	1.181^a	0.013	1.150^b	0.010	1.137^b	0.011
Net reproductive rate (R_o)	94.542^a	25.23	76.714^ab	20.679	61.228^b	17.610
Mean generation time (T)	27.255^c	0.573	30.967^b	0.272	31.917^a	0.301
Gross reproductive rate (GRR)	183.42^a	8.055	146.45^ab	32.83	136.77^b	30.553

LC (lethal concentration), SE (standard error), df (degree of freedom), means sharing similar letters in a row are not different statistical at 5% probability

sexes of the existing population (Rahmani and Bandani 2013; Huang and Chi 2013). The intrinsic rate of increase, reproductive rate and total oviposition period are the most important characteristics of the life table study to predict the insect population effected by insecticides (Papachristos and Milonas 2008).

The sub-lethal concentrations (LC₂₀ and LC₅₀) of novaluron for E. vittella were calculated as 2.224 and 9.837 mg L^-1, respectively in this study. Cutler et al. (2005) studied the acute toxicity of novaluron on the second instar of L. decemlineata and calculated LC₅₀ as 18.7 ppm and categorized it as broad-spectrum insecticides. Population parameters of E. vittella studied in this paper showed that the sub-lethal (LC₂₀ and LC₅₀) concentrations of novaluron have decreased the intrinsic rate of increase, finite rate of increase, reproductive value, survival rate, and net reproductive rate, however, the larval period, pupal period and TPOP were increased by the sub-lethal concentrations. The above results proved that the population growth of E. vittella was significantly reduced by the sub-lethal concentrations of novaluron. These results are according to the sub-lethal effects of thiamethoxam on Bradysia odoriphaga (Zhang et al. 2015). Significantly no difference was found in the adult pre-oviposition period (APOP) among treatments, while a significant variation was found in the total pre-oviposition period (TPOP), which was positively correlated with the intrinsic rate of increase of the E. vittella. Sub-lethal concentrations significantly prolonged the larval duration, this may have occurred because of agitations in nerve tissue development by neurotoxic chemical contact (Desneux et al. 2007). Similar results were found when the population of E. vittella treated with sublethal doses of lufenuron (Hafeez et al. 2019). The reason for the prolonged larval duration would be that the treated larvae were more intense with the detoxification of the sub-lethal effect of novaluron causing the increased larval period as compared to the control (Meng et al. 2018). The number of eggs per female also reduced to a significant level by the application of sub-lethal concentrations of novaluron. This showed that the chemical has produced some effects on the ovaries of the females in treated groups (Seth et al. 2004; Qu et al. 2017). It has been found that exposure of insects to insecticides results in the reduction of ovarioles size, basal oocytes, and firmness of follicular epithelium of armyworm, which was the main reason for reduced fecundity (Perveen and Miyata 2000). The reduction may also be due to changes in the behavioral and physiological effects of the insecticide. The short life span of adults will result in the short mating periods,

Fig. 1: Age-stage specific survival rate (s_xj) of E. vittella exposed to sublethal concentration of novaluron

which will ultimately result in fewer eggs in the field and thus a decline will be found in the field population over time. In this study, the population parameters viz., intrinsic rate of increase, gross reproductive rate, net reproductive rate and finite rate of increase were decreased with the LC₂₀ and LC₅₀ treatments. These results are in line with the result of previous studies, in which the intrinsic rate of increase, finite rate of increase and net reproductive rate statistically declined in diamondback moth and cabbage aphid by the treatment of spinosad and imidacloprid respectively (Lashkari et al. 2007; Yin et al. 2008). This study provides a clear knowledge about the population dynamics of E. vittella subjected to the sub-lethal effects of the insecticides. These sublethal concentrations of novaluron can be utilized in the field to delay the development rate and reduce the reproduction ability of the females in the pest population. These

Fig. 2: Survival rate (l_x) and fecundity of E. vittella exposed to sublethal concentration of novaluron

concentrations will reduce the number of insecticides used in fields, reduce the risk of resistance development in the insect pests and reduce environmental pollution.

Conclusion

This study publicized that the novaluron with sub-lethal concentrations significantly decreased the biological rate of E. vitella in the laboratory conditions and advocates the implementation of such doses in the fields for incorporation in integrated pest management strategies.

Author Contributions

DK, AG, BR and MT designed the research. DK, SK and SA conducted the experiments. BR and DK analyzed the data. DK, BR and IH wrote the manuscript. All the authors read and approved the manuscript.

Conflict of Interest

Authors declare that there is no conflict of interest

Funding Source

There is no funding source for the present research

Fig. 4: Reproductive value (V_xj) of E. vittella exposed to sublethal concentration of novaluron

Fig. 3: Life expectancy (e_xj) of E. vittella exposed to sublethal concentration of novaluron

References

Abbas N, SA Shad (2015). Assessment of resistance risk to lambda-cyhalothrin and cross-resistance to four other insecticides in the house fly, Musca domestica L. (Diptera: Muscidae). Parasitol Res 114:2629‒2637

Abbas N, SA Shad, M Razaq, A Waheed, M. Aslam (2014). Resistance of Spodoptera latera (Lepidoptera: Noctuidae) to profenofos: Relative fitness and cross-resistance. Crop Prot 58:49‒54

Ahmad M, B Rasool, M Ahmad, DA Russell (2019). Resistance and synergism of novel insecticides in field populations of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) in Pakistan. J Econ Entomol 112:859‒871

Al-Mehmmady RM (2000). Biological studies on the okra moth, Earias vittella (F.) (Lepidoptera: Noctuidae) in Jeddah, Saudi Arabia. Res Bull 96:5‒18

Aziz MA, MU Hasan, A Ali, J Iqbal (2012). Comparative efficacy of different strategies for management of spotted bollworms, Earias spp. on Okra, Abelmoschus esculentus (L.). Moench. Pak J Zool 44:1203‒1208

Aziz MA, M Hasan A Ali (2011). Impact of abiotic factors on incidence of fruit and shoot infestation of spotted bollworms Earias spp. on okra (Abelmoschus esculentus L.). Pak J Zool 43:863‒868

Chi H (2017). TWOSEX-MSChart: A computer program for the age-stage, two-sex life table analysis http://140.120.197.173/Ecology

Chi H (1988). Life-table analysis incorporating both sexes and variable development rates among individuals. Environ Entomol 17:26–34

hi H, H Liu (1985). Two new methods for the study of insect population ecology. Bull Inst Zool Acad Sin 24:225–240

Cutler GC, CD Scott‐Dupree, JH Tolman, CR Harris (2005). Acute and sublethal toxicity of novaluron, a novel chitin synthesis inhibitor, to Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). Pest Manage Sci 61:1060‒1068

Desneux N, A Decourtye, JM Delpuech (2007). The sublethal effects of pesticides on beneficial arthropods. Annu Rev Entomol 52:81‒106

Goodman D (1982). Optimal life histories, optimal notation, and the value of reproductive value. Amer Nat 119:803–823

Gulzar A, DJ Wright (2014). Fluctuating asymmetry, morphological changes and flight muscle ratio in a Vip3A resistant subpopulation of Heliothis virescens (WF06). Intl J Agric Biol 16:416–420

Hafeez M, S Jan, M Nawaz, E Ali, B Ali, M Qasim, GM Fernandez-Grandon, M Shahid, M Wang (2019). Sub-lethal effects of lufenuron exposure on spotted bollworm Earias vittella (Fab): Key biological traits and detoxification enzymes activity. Environ Sci Pollut Res 26:14300–14312

Han W, S Zhang, F Shen, M Liu, C Ren, X Gao (2012). Residual toxicity and sublethal effects of chlorantraniliprole on Plutella xylostella (Lepidoptera: Plutellidae). Pest Manage Sci 68:1184–1190

Huang YB, H Chi (2013). Age‐stage, two‐sex life tables of Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) with a discussion on the problem of applying female age‐specific life tables to insect populations. Ins Sci 19:263–273

Ishaaya I, A Barazani, S Kontsedalov, AR Horowitz (2007). Insecticides with novel modes of action: Mechanism, selectivity and cross‐resistance. Entomol Res 37:148–152

Ishaaya I, S Kontsedalov, AR Horowitz (2003). novaluron (Rimon), a novel IGR: Potency and cross‐resistance. Ins Biochem Physiol 54:157–164

Jan MT, N Abbas, SA Shad, MA Saleem (2015). Resistance to organophosphate, pyrethroid and biorational insecticides in populations of spotted bollworm, Earias vittella (Fabricius) (Lepidoptera: Noctuidae), in Pakistan. Crop Prot 78:247–252

Lashkari MR, A Sahragard, M Ghadamyari, (2007). Sublethal effects of imidacloprid and pymetrozine on population growth parameters of cabbage aphid, Brevicoryne brassicae on rapeseed, Brassica napus L. Ins Sci 14:207–212

Lohmeyer KH, JM Pound (2012). Laboratory evaluation of novaluron as a development site treatment for controlling larval horn flies, house flies, and stable flies (Diptera: Muscidae). J Med Entomol 49:647–651

Meng QW, JJ Wang, JF Shi, WC Guo, GQ Li (2018). Effect of teflubenzuron ingestion on larval performance and chitin content in Leptinotarsa decemlineata. Amer J Potato Res 95:463–472

Papachristos DP, PG Milonas (2008). Adverse effects of soil-applied insecticides on the predatory coccinellid Hippodamia undecimnotata (Coleoptera: Coccinellidae). Biol Cont 47:77–81

Perveen F, T Miyata (2000). Effects of sublethal dose of chlorfluazuron on ovarian development and oogenesis in the common cutworm Spodoptera litura (Lepidoptera: Noctuidae). Ann Entomol Soc Amer 93:1131–1137

Popp J, K Hantos (2011). The impact of crop protection on agricultural production. Stud Agric Econ 113:47–66

Praveen K, AS Sajjan, R Patil, P Dharmatti, M Kurdikeri (2007). Influence of seed treatment and foliar spray with insecticides and neem products on growth and seed yield in okra (Abelmoschus esculentus [L] Moench). Karnat J Agric Sci 20:388–390

Qu CW, F Zhang, G Li, CL Tetreau, R Wang (2017). Lethal and sublethal effects of dinotefuran on two invasive whiteflies, Bemisia tabaci (Hemiptera: Aleyrodidae). J Asia Pac Entomol 20:325–330

R Development Core Team (2009). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna http://www.R-project.org

Rahman MA, MM Uddin, MA Haque, MM Rahman (2016). Comparative efficacy of different tactics for the management of okra shoot and fruit borer, Earias Vittella (Fab.) under field condition. Intl J Appl Sci Biotechnol 4:74–78

Rahmani S, AR Bandani (2013). Sublethal concentrations of thiamethoxam adversely affect life table parameters of the aphid predator, Hippodamia variegate (Goeze) (Coleoptera: Coccinellidae). Crop Prot 54:168–175

Rasool B, J Arif, M Hamed, S Nadeem (2002). Field performance of Trichogramma chilonis against Helicoverpa armigera under varying sowing times and varieties of cotton. Intl J Agric Biol 4:113–114

Rehan A, S Freed (2015). Fitness cost of methoxyfenozide and the effects of its sublethal doses on development, reproduction, and survival of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Neotrop Entomol 44:513–520

Seth RK, JJ Kaur, DK Rao, SE Reynolds (2004). Effects of larval exposure to sublethal concentrations of the ecdysteroid agonists RH-5849 and tebufenozide (RH-5992) on male reproductive physiology in Spodoptera litura. J Ins Physiol 50:505–517

Umrao RS, S Singh, J Kumar, D Singh, D Singh (2013). Efficacy of novel insecticides against shoot and fruit borer (Earias vittella Fabr.) in okra crop. Hortic Flor Res Spectr 2:251–254

Yin XH, QJ Wu, XF Li, YJ Zhang, BY Xu (2008). Sublethal effects of spinosad on Plutella xylostella (Lepidoptera: Yponomeutidae). Crop Prot 27:1385–1391

Zhang RM, EB Jang, SCJ He (2015). Lethal and sublethal effects of cyantraniliprole on Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). Pest Manage Sci 71:250–256