Insecticidal effect on a population of Spilarctia obliqua (Lepidoptera: Arctiidae)

RESEARCH PAPER

Insecticidal effect on a population of Spilarctia obliqua(Lepidoptera: Arctiidae)M. Shafiq ANSARI, Haidar ALI and Shazia SHAFQAT

Department of Plant Protection, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, India

Correspondence

M. Shafiq Ansari, Department of PlantProtection, Faculty of Agricultural Sciences,Aligarh Muslim University, Aligarh, UP202002, India.Email: [email protected]

Received 30 September 2010;accepted 7 November 2011.

doi: 10.1111/j.1748-5967.2012.00478.x

Abstract

Survivors of Spilarctia obliqua derived from 3rd instars that had ingested LC50 ofimidacloprid (0.025%), dichlorvos (0.014%) and endosulfan (0.012%) werestudied through the life table method. Survivorship was reduced in insecticideexposed populations as compared to 45-day in the control groups. Egg hatchingwas significantly decreased for the insecticide treated populations. Total larvalmortality was the highest for endosulfan (36.76%) as compared to the individualsthat died among control groups (14.29%). Life expectancy (ex) was decreasedgradually over time and stage of development for insecticides tested and the controlgroups. Dichlorvos (0.014%) has caused a significant reduction in the potentialfecundity i.e. 315 females/female/generation, while 415 in the unexposed cohorts.Net reproductive rate (Ro) was the lowest in endosulfan (118.47 females/female/generation) treatment followed by dichlorvos (141.97), imidacloprid (144.49) andthe control groups (272.42). Similarly, the intrinsic rate of increase (rm) wassubstantially decreased after exposure with endosulfan (0.124 females/female/day)as compared to 0.135 in the unexposed cohort. The finite rate of increase (l) wasnot significantly different among the insecticide treatments and control groups.Mean generation time was significantly reduced after exposure to dichlorvos(37.19 days). However, 41.34 days were required to complete one generation byS. obliqua in the absence of insecticides. Based on these results, population ofS. obliqua would double in 5.19 days under the influence of dichlorvos whilerequiring 5.13 days for unexposed cohorts.

Key words: doubling time, intrinsic rate of increase, potential fecundity, Spilarctia obliqua.

Introduction

Spilarctia obliqua (Walker) (Lepidoptera: Arctiidae) is asporadic and polyphagous insect pest that attacks 126 plantspecies belonging to 25 families including 25 weed species(Singh & Singh 1995). A major outbreak occurred in Sep-tember 1975 in Bihar, India causing severe damage to dif-ferent oilseeds and edible legume crops (Sinha et al. 1975).It is distributed throughout much of the Oriental region(Goel et al. 2004). The young caterpillars feed gregariouslyon younger leaves, leaving behind the midrib. Older cater-pillars feed voraciously on leaves, soft stems and branchesand may denude the crop within a few days. S. obliqua

breeds from March to April and July to November underdifferent agro climatic conditions. It passes the hottestpart of summer (May–June) and winter (December toFebruary) in the pupal stage among plant debris (Atwal &Dhaliwal 1986). Indiscriminate use of toxic insecticidesfor the management of this pest (Kundu 1991; Jaglan &Sircar 1997) results in environmental pollution, hazards tobeneficial organisms, and the development of resistance(Perry et al. 1998). Consequently, a comprehensive inte-grated pest management (IPM) program is needed toreduce its density below the economic threshold withthe judicious selection and timing of applications ofinsecticides.

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Lethal concentrations (LC) are commonly used to assessthe pesticide toxicity to arthropods (Overmeer & Van Zon1982; Stark & Rangus 1994) but they do not properly assessthe population-level effect of the chemicals (Forbes &Calow 1999; Stark & Banken 1999; Stark & Banks 2003).Determining the efficacy of pesticide requires informationabout the life history and behavior of the pest species (Carey1993; Wennergren & Stark 2000; Stark et al. 2004). There-fore, Stark and Wennergren (1995) have proposed demo-graphic toxicological analysis that incorporated the life tableparameters in the context of toxicology. It is a process thatallows comparison of the life table parameters for unexposedpopulations with those exposed to various concentrationsand the types of toxicants. Therefore, it is an appropriateapproach that takes into account all the biological parametereffects that a toxicant might have at the levels of organiza-tion higher than the individual (Stark et al. 1997, 1998,2004). Life table response experiments (LTREs) are beingincreased to measure multiple endpoints of the effects thathave been recommended as a superior laboratory toxicologi-cal endpoint (Stark et al. 1997).

Population growth rate, especially increase of the intrinsicrate (rm) has been recommended together with LC estimatesfor toxicity assessments to provide a more accurate estimateof population-level-effects of toxic compounds (Walthall &Stark 1996; Stark et al. 1997; Forbes & Calow 1999). Dixon(1987) has also suggested that the rm provides an effectivesummary of an insect’s life history traits. Stark et al. (2007)have strongly advocated that the most widely used measuresof effect in LTREs are the rm because a total measure of thepopulation-level effect can be determined with one number.When the rm is zero, the population is stable (unchanging),when the rm is a positive number, the population is increasingexponentially and when the rm is negative, the population isdeclining exponentially towards extinction. For a finite rateof increase (l), a population multiplication rate value of oneindicates a stable population, numbers greater than one indi-cate a growing population and numbers lower than one indi-cate a population decline.

LC50 will reduce the number of individuals by half and the50% individuals that survived from exposure will be studiedthrough the life table analysis. The objective of this study isto determine the differential effects of commonly used insec-ticides on the life table of S. obliqua. Few studies have beenpublished on the use of demography and similar measures ofpopulation growth rate are determined to evaluate the effectof pesticides on insect mortality, growth and development(Stark et al. 1997; Stark & Banks 2003; Rezaei et al. 2007).These results will finally provide a better understanding andprediction of the total effect of an insecticide at the popula-tion level of a species (Kareiva et al. 1996) thus providing acomplete time series portrait of toxicology (Forbes & Calow1999).

Imidacloprid, a chloronicotinyl insecticide, was intro-duced to landscape pest management in the early 1990’s(Sclar et al. 1998). Its systemic activity, low mammaliantoxicity, and effectiveness against a wide range of pests:aphids, scale insects, whiteflies, Coleoptera and Lepidopterawhich makes it as an attractive choice for a number of plantprotection programs (Mullins 1993). Imidacloprid has amixed reputation regarding its safety to natural enemies ofpests (Kunkel et al. 1999; James & Vogele 2001). It hasmode of action similar to that of nicotine, functioning as anagonist on the nicotine acetylcholine receptor to the postsy-naptic membrane (Boyd & Boethel 1998). Elbert et al.(1991) have also suggested that the toxicity of imidaclopridis strongly dependent on the developmental stages andmethod of exposures. Endosulfan, a cyclodiene compound,antagonizes the action of the neurotransmitter, gamma-aminobutyric acid (GABA) which induces the uptake ofchloride ions by neurons. The blockage of this activity by acyclodiene insecticide results in only a partial repolarizationof the neuron and a state of uncontrolled excitation isobserved (Klaassen & Watkins 1999). Dichlorvos, an orga-nophosphate, exerts its effects by inhibiting esterases, espe-cially acetyl cholinesterase (AChE) (Wang et al. 2004).AChE is a key enzyme that terminates nerve impulses bycatalyzing the hydrolysis of the neurotransmitter, acetylcho-line in the nervous system. It is a contact and stomachinsecticide with fumigant and penetrant in action. Dichlor-vos is rapidly lost from leaf surfaces by volatilization andhydrolysis.

Material and methods

Maintenance of stock culture

Caterpillars of S. obliqua were collected from castor plantsin the district of Aligarh, Uttar Pradesh, India. They werekept in jars measuring 20 ¥ 10 cm containing fresh castorleaves for feeding. Tops of the jars were covered over by amuslin cloth and secured with rubber bands to preventescape. These jars were then kept at 30 � 1°C and 80 � 5%relative humidity. In order to maintain hygienic condition,food was changed every 24-h prior to pupation. Pupae weresorted and kept in separate jars (20 ¥ 10 cm) for emergence.After emergence, one male and female was kept in a jar andprovided a 10% sugar solution soaked in cotton wool forfeeding and 3–4 strips of white paper sheets were hung fromthe top of each jar for resting and oviposition. Eggs wereremoved from the jars and the paper strips using a soft haircamel brush and transferred to Petri plates over castor leavesfor hatching. Freshness of leaf was maintained by wet cottonwrapped around the leaf petiole. This method was repeatedthroughout the 4th generation to acclimatize S. obliqua underlaboratory conditions.

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Insecticides

The commercial formulations of Imidacloprid (200% SLM/S Bayer India, Mumbai, India), Dichlorvos (76% EC M/SUnited Phosphorus Ltd, Mumbai, India) and Endosulfan(35% EC M/S Insecticide (India) Ltd, Delhi, India) wereused.

Insecticide bioassay

LC50 values for imidacloprid, dichlorvos and endosulfanwere determined against 3rd instars of S. obliqua by theleaf-dip bioassay method. Six concentrations of eachinsecticide were prepared in distilled water. A total of 30newly moulted 3rd instars were obtained from stock cul-ture and starved for 2-h for testing at each concentration.Pieces of castor leaves were dipped for 10 sec in each con-centration of an insecticide and air dried at room tempera-ture. Impregnated leaves were then kept in plasticcontainers (500 mL) and five larvae were released intoeach container and allowed to feed for 24-h. Concurrently,five larvae were released on a non-treated leaf (control)and replicated 6 times for each treatment. The containerwith the treated leaf was changed and a fresh castor leafwas provided to the larvae. Mortality counts which alsoincluded moribund larvae were made at 24 h after treat-ment. Corrected mortality was obtained using Abbott’s(1925) formula. Mortality data was subjected to ProbitAnalysis (Finney 1952) to determine LC50 values for eachinsecticide.

Treatment of LC50 of insecticides

LC50 solution of insecticides; imidacloprid (0.025%),dichlorvos (0.014%) and endosulfan (0.012%) were pre-pared in distilled water. Pieces of castor leaves weredipped separately for 10 sec in each solution and air driedat room temperature. A total of 45 newly moulted 3rd

instars were obtained from stock culture and starved for2-h for testing each insecticide. For the control groups,castor leaves were dipped in distilled water and then airdried at room temperature and the same numbers of 3rd

instars were used as with each treatment. An impregnatedleaf was placed in a glass jar (250 mL) and then a singlelarva was released into it and allowed to feed for 24-h.The jar and impregnated leaf was changed 24-h aftertreatment and fresh castor leaf was provided to the larva.Food was changed daily prior to pupation. Emerged adultswere transferred into separate jars (20 ¥ 10 cm) and pro-vided a 10% sugar solution soaked in cotton as a foodsource.

Life table of S. obliqua under the influence of LC50

of insecticides

Surviving adults that had obtained from treatments express-ing LC50 values for imidacloprid, dichlorvos and endosulfanwere paired to evaluate the life table of S. obliqua. Foreach treatment, freshly oviposited eggs of S. obliqua werecounted by means of a hand lens (10X). The eggs were thenkept in batches of 100 (cohort) and replicated 10 times forconstruction of life table. Hatched eggs were counted and 1st

instars were transferred to jars with each jar (10 ¥ 10 cm)containing 5 larvae and 20 jars were used for each replicate.The experiment was replicated 10 times. Fresh castor leaveswere provided to the larvae and changed daily prior to pupa-tion. Observations were made daily on the larval and pupaldurations. Emerged adults from the treated and controlcohorts were then counted and sexed to determine the agespecific fecundity. Ten pairs of males and females were keptin separate jars (20 ¥ 10 cm) and replicated three times forthe treated and control groups. Adults were provided a 10%sugar solution soaked in cotton as a food source. Eggs laidby each female were recorded daily from the day after emer-gence till death. The numbers of eggs were divided on thebasis of 1:1 sex ratio to obtain the number of female birth(mx). Life table was constructed by method of Deevey(1947) and Southwood (1978). Expectancy of life (ex =Tx/Ix), Potential fecundity (Pf = Smx) and Net reproductiverate (Ro = Slx. mx) was determined. Intrinsic rate of increase(rm) was calculated by the formula given by Birch (1948)which is: Se-rm x.lx.mx = 1 and finite rate of increase (l) =Anti loge rm was also estimated. Mean generation time (Tc) isthe mean period over which progeny are produced that iscalculated by the formula: Tc = lx.mx.x/lx.mx. Corrected gen-eration time (t) is defined as the period from birth of theindividuals to birth of offspring and estimated by t = loge

Ro/rm. Doubling time (DT) is defined as the time required forthe population to double its number that is calculated as:DT = loge 2/rm.

Data analysis

Population parameters were analyzed using written compu-ter software. Difference in the above parameters for thetreatment and the control groups were compared using theone-way analysis of variance (ANOVA), Minitab-11 forWindows, unless stated otherwise. The mean values werecompared using Duncan’s Multiple Range Test (DMRT) totest the significant difference.

Results

Survivorship (P = 0.59; d.f. = 3, 11; P = 0.05) of immatureand adult stages of S. obliqua was decreased after treat-

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ment with imidacloprid (F = 39.38; d.f. = 2, 42; P = 0.05),dichlorvos (F = 192.28; d.f. = 2, 42; P = 0.05) and endo-sulfan (F = 221.97; d.f. = 2, 43; P = 0.05) (Fig. 1). Egghatching was significantly (F = 0.55; d.f. = 3, 11; P = 0.05)decreased for the insecticide exposed populations. A totalof 32% unhatched eggs were observed after the exposurewith endosulfan (0.012%), while 9% in the control groups.Larval survival was significantly (F = 15.48; d.f. = 3, 11; P= 0.05) reduced to 63.23% by endosulfan treatment ascompared to 85.71% for the control groups (Table 1). The

highest larval mortality was observed among individualsexposed to endosulfan (36.76%) and the lowest for controlgroups (14.29%) (Fig. 1). Pupal duration was 10 days inthe endosulfan treatment and 13 days in the control groups.Pupal survival was 89.36% in the imidacloprid exposedpopulation as compared to 87.17% in the control groups.Adult emergence was significantly (F = 33.55; d.f. = 3, 11;P = 0.05) reduced to 39% under the influence of endosul-fan, while 68% in the control groups (Table 1). Lifeexpectancy (ex) of exposed and unexposed individuals was

Figure 1 Effect of insecticides onsurvivorship, mortality and expectancyof S. obliqua. , Untreated; ,Imidacloprid; , Dichlorvos; ,Endosulfan.

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high in the early stage of development and then decreasedgradually over times (Fig. 1).

Female survivorship was high in the beginning anddecreased slowly in exposed and unexposed individuals(Fig. 2). Female longevity was 7 days in the treatment

groups as compared to 5 days in control. Unexposed femalessignificantly laid more eggs than the insecticide exposedindividuals. The daily fecundity rate (mx) was significantlyhigher in the beginning of female survivorship for bothexposed and unexposed populations than to the advancing

Table 1 Effect of insecticides on the survival of S. obliqua

Treatment Mean No. larvae % Larval survival Mean No. pupae % Pupal survival Emergence of adult

Imidacloprid (0.025%) 47.00 � 2.15b 63.51 � 1.74b 47.00 � 1.88b 89.36 � 2.12a 42.00 � 1.68b

Dichlorvos (0.014%) 51.00 � 2.22b 64.55 � 2.30b 51.00 � 2.27b 92.15 � 1.78a 47.00 � 1.72b

Endosulfan (0.012%) 43.00 � 2.20c 63.23 � 2.18b 43.00 � 1.86c 90.69 � 2.16a 39.00 � 2.82c

Untreated 78.00 � 2.14a 85.71 � 2.28a 78.00 � 2.26a 87.17 � 1.74a 68.00 � 2.20a

L.S.D. (P = 0.05) 7.16 8.38 6.14 8.18 5.18F- value (df = 3,11) 29.46 15.48 42.82 32.54 33.55Sem � 2.28 2.24 2.16 2.31 2.42

Values not followed by the same letter are significantly different (P < 0.05) by Duncan’s Multiple Range Test (DMRT).

Figure 2 Effect of insecticides on fecundity (mx) and female survivorship (lx) of S. obliqua. , mx; , lx.

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age (Fig. 2). Post oviposition period was prolonged to 3 daysin dichlorvos treated females as compared to 1 day in thecontrol groups.

Dichlorvos (0.014%) has caused a significant (P < 0.05)reduction in the potential fecundity (Pf) as compared toimidacloprid and endosulfan and also was significantlylower than the control groups (Table 2). The net reproductiverate (Ro) was significantly decreased for the treatmentgroups as compared to control (F = 18; d.f. = 3, 11;P = 0.05). The Ro was lowest (118.47 females/female/generation) for endosulfan and the highest (272.42) occurredin the control groups. The intrinsic rate of increase (rm) waslowest for groups treated with endosulfan (0.124 females/female/day) compared to the control (0.135). The finite rateof increase (l) was smallest for endosulfan (1.152females/female/day) but was not significant among insecticide treat-ments and the control groups. Mean generation time (Tc)was significantly reduced among treatment groups as com-pared to the control with the similar results were obtained forcorrected generation time (t). Fractional difference was cal-culated in doubling time (DT) for both treatments and thecontrol groups.

Discussion

Exposure to pesticides may result in a wide range of effectson an organism (Banks et al. 2007, 2008). In addition todeath, exposure can result in shortened life span, reducednumber of offspring, changes in the time of first reproduc-tion, prolonged generation times, weight loss, and the muta-tion in offspring (Stark & Banks 2003) and may also lead topopulation decline and collapse (Stephens & Sutherland1999). The fluctuation in biological parameters in the pesti-cide treated populations may reflect changes observed in thestructures or the function of carboxyl esterase and glutath-

ione transferases are increased as compared to the untreatedpopulations (Yin et al. 2008b). Moreover, Stark (2005) hassuggested that the effects of toxicants on the population leveldiffered greatly and exposure to diazinon resulted in a popu-lation larger than expected, and the majority of the pesticidesand adjuvant have caused population extinction over a 10days period. Population dynamics of Apolygus lucorum wasseverely disrupted after application of endosulfan (Liu et al.2008) and also significantly reduced the longevity andfecundity of females.

In the present study, survivorship was decreased in theimmature and adult stages after exposure to insecticides.Reduction in survivorship was also observed forAcyrthosiphum pisum (Stark & Wennergren 1995), Brevico-ryne brassicae (Lashkari et al. 2007) and Plutella xylostella(Ansari et al. 2008; Yin et al. 2009). Egg hatching of S. obli-qua was decreased in the treatment groups which may be theresult of inappropriate incorporation of yolk so that embryofailed to complete the developmental phase (Kaur et al.1993). However, Kumar and Chapman (1984) have alsosuggested that the reduction in hatching may be due to theinability of embryos to perforate the surrounding vitellinemembrane because chitinous mouth hook assembly becomeweak which is required for hatching (Wilson & Cryan 1997),as well as a direct toxic effect of the insecticide which hadbeen left unmetabolized in the body of the parents that mayalso be incorporated in the eggs (Abd-Elghafar et al. 1991).Mortality at immature (larval and pupal) and adult stages ofS. obliqua was high and varied in the treatment groups. Starkand Wennergren (1995) found concentration dependentdeath rate in A. pisum by Margosan-O. However, mortalitycaused by pesticides was significantly higher than thecontrol (Rezaei et al. 2007).

Reduction of fecundity was observed in the treatmentgroups that may be due to an inhibitory effect on

Table 2 Effect of insecticides on life indices of S. obliqua

Life parametersImidacloprid

(0.025%)Dichlorvos(0.014%)

Endosulfan(0.012%) Untreated

LSD(P = 0.05)

F- value(df = 3,11)

Potential fecundity (Pf = Smx) 351.00 � 6.57b 315.00 � 8.08c 322.00 � 5.77c 415.00 � 8.47a 22.80 4.79Net reproductive rate (Ro = lx.mx) 144.49 � 1.15b 141.97 � 1.13c 118.47 � 1.73d 272.42 � 2.88a 2.47 18.00Intrinsic rate of increase

(e-rmx.lxmx = 1)0.129 � 5.77e-3a 0.133 � 5.72e-3a 0.124 � 5.77e-3a 0.135 � 5.6e-3a 0.02 0.34

Finite rate of increase(l = Anti loge rm)

1.227 � 0.57a 1.237 � 0.52a 1.225 � 6.35e-3a 1.229 � 0.02a 0.07 8.43

Mean length of generation(Tc = lx.mx.x/Ro)

38.32 � 0.56b 37.19 � 0.10c 38.27 � 0.57b 41.34 � 0.52a 0.70 15.51

Corrected generation time(t = loge Ro/rm)

38.34 � 0.55b 37.14 � 0.57c 38.28 � 0.59b 41.53 � 0.50a 0.24 18E+04

Doubling time (DT = loge2/rm) 5.30 � 0.03b 5.19 � 0.05b 5.55 � 0.07a 5.13 � 0.08b 0.18 0.12

Values not followed by the same letter are significantly different (P < 0.05) by Duncan’s Multiple Range Test (DMRT).

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reproductive development or inhibition of oviposition byblocking necessary endocrine secretions (Pratt et al. 1980)or inhibition of ovarian development as well as malforma-tion of oviposition organs (Asai et al. 1985) and inhibition ofvitellogenesis (Taneja et al. 1979). Parental reproductivephysiology may also be disrupted because of disturbances ofneurosecretory system after application of insecticides (Sod-erlund & Bloomquist 1989) and also neurohormone imbal-ances, which may affect the normal function of reproduction(Maddrell & Reynolds 1972). Fecundity of P. xylostella wassignificantly decreased by imidacloprid (0.002%) (Ansariet al. 2008). Yin et al. (2008a) reported that survivingfemales of P. xylostella obtained from 3rd instars treatedwith LC25 of spinosad laid smaller eggs, which showed alower percentage of hatching (fertility) than the control.Lashkari et al. (2007) also found that fecundity of thecontrol groups was significantly greater than those treatedwith imidacloprid.

The net reproductive rate (Ro) of S. obliqua was signifi-cantly reduced in treatment groups as compared to thecontrol. Kaur et al. (2001) found that the number of femalesover generation (Ro) declined as a function of pesticidesconcentrations and it was supported by Stark and Wenner-gren (1995) that Ro was significantly decreased as a functionof pesticide.

Most of the pesticides have an ability to decrease theintrinsic rates of increase (rm) for some insects (Jackson &Peterson 2000; Lashkari et al. 2007). The rm was substan-tially decreased in treated groups as compared to the controlin the present study. It was reduced in a concentrationdependent manner when neonates of A. pisum were exposedto concentrations of Morgosan-O and become negative at60 ppm of azadirachtin showing that the population wouldbe at the verge of extinction (Stark & Wennergren 1995).Walthall and Stark (1996) have found a decrease in the rm

after exposure of imidacloprid on A. pisum. A significantreduction has occurred in the rm when populations ofB. brassicae were exposed to imidacloprid and pymetrozine(Lashkari et al. 2007) and also reduced when P. xylostellaingested imidacloprid (Ansari et al. 2008) but a slightlyhigher rm values were observed by Boykin and Campbell(1982) when mites were fed on peanut leaves treated withmancozeb, carbaryl, mancozeb+ carbaryl verses those fed onuntreated leaves. Li et al. (2006) reported that the intrinsicrate of increase of mites was significantly delayed after thejuvenile stages were treated with chlofentezine. However,neither an increase nor decrease was observed in the rm ofA. gossypii when exposed to bifenthrin, acephate or carbo-furon (Kerns & Stewart 2000).

Mean generation time (Tc) of S. obliqua was significantlydiffered in the treatments and control groups, which issimilar to the work of Stark and Wennergren (1995) whoreported that the mean generation time was declined as the

pesticide concentration increased. Populations exposed atbirth were more affected than that of exposed as adults. Itwas confirmed by Lashkari et al. (2007) when B. brassicaewas exposed to sublethal concentrations of imidacloprid andpymetrozine. However, generation time was prolonged in aconcentration dependent manner when A. pisum wasexposed to imidacloprid (Walthall & Stark 1996) and the Tc

was increased to 35% after application of imidacloprid,propargite and pymetrozine on Chrysoperla carnea (Rezaeiet al. 2007). Doubling time of populations may reflect anincrease in the time it takes for survivors to compensatefor the loss of individuals. Unexposed population of S. obli-qua will double in 4.91 days while fractional differenceswere observed among the treated groups. Groups ofB. brassicae exposed to imidacloprid had more time to com-pensate for the loss of individuals (Lashkari et al. 2007) andthe same result is reported by Ansari et al. (2008) that theimidacloprid (0.002%) has prolonged the doubling time ofP. xylostella.

It is concluded that insecticides caused a significant effecton the survival and mortality of S. obliqua. Endosulfan anddichlorvos significantly reduced the fecundity, reproductiverate and intrinsic rate of increase of the population of S. obli-qua and their suitability as selective insecticides. Therefore,these insecticides may be valuable for the integrated pestmanagement and insecticide resistance management onoilseeds and edible legume cultivating areas and other crop-ping systems.

References

Abbott WS (1925) A method of computing the effectiveness of aninsecticide. Journal of Economic Entomology 18: 265–267.

Abd-Elghafar SF, Appel AG, Mack TP (1991) Effects of severalinsecticide formulations on oothecal drop and hatchability inGerman cockroaches (Dictyoptera: Blattellidae). Journal ofEconomic Entomology 84: 502–509.

Ansari MS, Ahmad T, Ali H, Gulrez H (2008) Effect of imida-cloprid on life table of Plutella xylostella (Linn.). Annals ofPlant Protection Sciences 16: 341–346.

Asai T, Kajihara OK, Fukuda M, Maekawa S (1985) Studies onthe mode of action of buprofezin. II. Effects on reproduction ofthe brown planthopper, Nilaparvata lugens Stal (Homoptera-:Delphacidae). Applied Entomology and Zoology 20: 111–117.

Atwal AS, Dhaliwal GS (1986) Agricultural Pests of South Asiaand Their Management, 449–450. Kalyani Publishers, NewDelhi.

Banks HT, Banks JE, Dick LK, Stark JD (2007) Estimation ofdynamic rate parameters in insect populations undergoing sub-lethal exposure to pesticides. Bulletin of Mathematical Biology69: 2139–2180.

Banks JE, Dick LK, Banks HT, Stark JD (2008) Time varyingvital rates in ecotoxicology: selective pesticides and aphidpopulation dynamics. Ecological Modelling 210: 155–160.

M. S. Ansari et al.

336 Entomological Research 42 (2012) 330–338© 2012 The Authors. Entomological Research © 2012 The Entomological Society of Korea and Wiley Publishing Asia Pty Ltd

Birch LC (1948) The intrinsic rate of natural increase of an insectpopulation. The Journal of Animal Ecology 17: 15–26.

Boyd ML, Boethel DJ (1998) Residual toxicity of selected insec-ticides to Heteropteran predaceous species (Heteropotera: Lyg-aeidae, Nabidae, Pentatomidae) on soybean. EnvironmentalEntomology 27: 154–160.

Boykin LS, Campbell WV (1982) Rate of population increase ofthe two spotted spider mite, Tetranychus urticae (Acaricide:Tetranychidae) on peanut Arachis hypogea leaves treatedwith pesticides. Journal of Economic Entomology 75: 966–971.

Carey JR (1993) Applied Demography for Biologists with SpecialEmphasis on Insects, 206 pp. Oxford University Press, NewYork.

Deevey ES (1947) Life table for natural populations of animals.Quarterly Review of Biology 22: 283–314.

Dixon AFG (1987) Parthenogenetic reproduction and the rate ofincrease in aphids. In: Minks AK, Harrewijn P (eds) Aphids:Their Biology, Natural Enemies and Control, Vol. A, pp. 269–287. Elsevier, Amsterdam, The Netherlands.

Elbert A, Becker B, Hartwig J, Erdelen C (1991) Imidacloprid, anew systemic insecticide. Pflanzenschutz Nachrichten Bayer44: 113–116.

Finney DJ (1952) Probit Analysis. Cambridge University Press,London.

Forbes VE, Calow P (1999) Is the per capita rate of increase agood measure of population-level effects in ecotoxicology?Environmental Toxicology and Chemistry 18: 1544–1556.

Goel SC, Kumar S, Bhardwaj DK (2004) Salient features andbibliography of Bihar hairy caterpillar, Spilosoma obliqua Wlk.(Lepidoptera: Arctiidae). Uttar Pradesh Journal of Zoology 24:1–31.

Jackson DM, Peterson JK (2000) Sublethal effects of resin glu-cosides from periderm of sweet potato storage roots on Plutellaxylostella (Lepidoptera:Plutellidae). Journal of EconomicEntomology 93: 388–393.

Jaglan RS, Sircar P (1997) Relative toxicity of synthetic pyre-throid emulsion formulations against larvae of Spilosomaobliqua (Walker) and Spodoptera litura (Fab.). Journal ofInsect Science (Online) 10: 52–54.

James DG, Vogele B (2001) The effect of imidacloprid on sur-vival of some beneficial arthropods. Plant Protection Quarterly16: 58–62.

Kareiva P, Stark JD, Wennergren U (1996) Using demographictheory community ecology and spatial models to illuminateecotoxicology. In: Baird DJ, Maltby L, Grey-Smith PW,Douben PET (eds) Ecological Dimensions, pp. 13–23.Chapman & Hall, London.

Kaur H, Sandhu R, Dhillon SS (1993) Substituted pyrimidine-2-thiols: a newly discovered group of antifertility agents againstred cotton bug. Indian Journal of Entomology 55: 396–403.

Kaur JJ, Rao DK, Sehgal SS, Seth RK (2001) Effect of hexaneextract of NSKE on development and reproduction behavior ofSpodoptera litura. Annals of Plant Protection Sciences 9: 171–178.

Kerns DL, Stewart SD (2000) Sublethal effects of insecticides onthe intrinsic rate of increase of cotton aphid. EntomologiaExperimentalis et Applicata 94: 41–49.

Klaassen CD, Watkins JB (1999) Casarett & Doull’s Toxicology:the Basic Science of Poisons, 5th edn, pp. 542–547. MacGraw-Hill Publ. Co., New York.

Kumar K, Chapman RB (1984) Sublethal effects of insecticideson the diamondback moth, Plutella xylostella (L). PesticideScience 15: 344–352.

Kundu GG (1991) Bihar hairy caterpillar, Spilosoma obliquaWalker (Lepidoptera: Arctiidae) on soybean. Indian Journal ofEntomology 53: 491–493.

Kunkel BA, Held DW, Potter DA (1999) Impact of halofenozide,imidacloprid and bendiocarb on beneficial invertebrates andpredatory activity in turf grass. Journal of Economic Entomol-ogy 93: 511–518.

Lashkari MR, Sahragard A, Ghadamyari M (2007) Sublethaleffects of imidacloprid and pymetrozine on population growthparameters of cabbage aphid, Brevicoryne brassicae on rape-seed, Brassica napus L. Insect Science 14: 207–212.

Li DX, Tian J, Shen ZR (2006) Assessment of sublethal effects ofclofentezine on life-table parameters in hawthorn spider mite(Tetranychus viennensis). Experimental and Applied Acarology38: 255–273.

Liu Y, Lu Y, Wu K, Wyckhuys KG, Xue F (2008) Lethal and sublethal effects of endosulfan on Apolygus lucorum (Hemi-ptera:Miridae). Journal of Economic Entomology 101: 1805–1810.

Maddrell SHP, Reynolds SE (1972) Release of hormones ininsects after poisoning with insecticides. Nature 236: 404–406.

Mullins JW (1993) Imidacloprid: a new nitro guanidine insecti-cide. In: Duke SO, Menn JJ, Plimmer JR (eds) Pest Controlwith Enhanced Environmental Safety, pp. 183–189. AmericanChemical Society Symposium-Report, Washington, DC.

Overmeer WPJ, Van Zon AQ (1982) A standardized methods fortesting the side effects of pesticides on the predacious mite,Amblyseius andersoni (Acarina:Phytoseiidae). Entomophaga27: 357–364.

Perry AS, Samamoto I, Ishaaya I, Perry RY (1998) Insecticides inAgriculture and Environment, 261 pp. Springer, Berlin.

Pratt GE, Jeuning RC, Hammett AH, Brooks GT (1980) Lethalmetabolism of precocene-I to a reactive epoxide by locustcarpora allata. Nature 284: 320–323.

Rezaei M, Talebi K, Naveh VH, Kavousi A (2007) Impacts of thepesticides imidacloprid, propargite and pymetrozine on Chrys-operla carnea (Stephens) (Neuroptera: Chrysopidae): IOBCand life table assays. Biocontrol 52: 385–398.

Sclar DC, Gerace D, Cranshaw WS (1998) Observations ofpopulation increases and injury by spider mites (Acaricide:Tetranychidae) on ornamental plants. Journal of EconomicEntomology 91: 250–255.

Singh I, Singh G (1995) Biology of Bihar hairy caterpillar, Spi-losoma obliqua (Walker) on sunflower in Punjab. Journal ofInsect Science (Online) 8: 48–54.

Effect of insecticides on Spilarctia obliqua

337Entomological Research 42 (2012) 330–338© 2012 The Authors. Entomological Research © 2012 The Entomological Society of Korea and Wiley Publishing Asia Pty Ltd

Sinha MM, Yadav RP, Kumar A (1975) Outbreak of Bihar hairycaterplillar, Diacrisia obliqua (Walker) in North Bihar. Ento-mological News 7: 3.

Soderlund DM, Bloomquist JR (1989) Neurotoxic actions ofpyrethroid insecticides. Annual Review of Entomology 34:77–96.

Southwood TRE (1978) Ecological Methods with Particular Ref-erences to the Study of Insect Population, 524 pp. Chapmanand Hall, London.

Stark JD (2005) How closely do acute lethal concentration esti-mates predict effects of toxicants on population? IntegratedEnvironmental Assessment and Management 1: 109–113.

Stark JD, Banken JAO (1999) ) Importance of population struc-ture at the time of toxicant exposure. Ecotoxicology and Envi-ronmental Safety 42: 282–287.

Stark JD, Banks JE (2003) Population level effects of pesticidesand other toxicants on arthropods. Annual Review of Entomol-ogy 48: 505–519.

Stark JD, Rangus TM (1994) Lethal and sublethal effects of theneem insecticide formulation, Margosan-O, on the pea aphid.Pesticide Science 41: 155–160.

Stark JD, Wennergren U (1995) Can population effects of pesti-cides be predicted from demographic toxicological studies?Journal of Economic Entomology 85: 1089–1096.

Stark JD, Banken JAO, Walthall WK (1998) The importance ofthe population perspective for the evaluation of side effects ofpesticides on beneficial species. In: Haskell PT, McEwen P(eds) Ecotoxicology: Pesticides and Beneficial Organisms, pp.348–359. Kluwer Academic Publishers, Dordrecht, The Neth-erlands.

Stark JD, Banks JE, Acheampong S (2004) Estimating suscepti-bility of biological of control agents to pesticides: influence oflife history strategies and population structure. BiologicalControl 29: 392–398.

Stark JD, Tanigoshi L, Bounfour M, Antonelli A (1997) Repro-ductive potential: its influence on the susceptibility of thespecies to pesticides. Ecotoxicology and Environmental Safety37: 273–279.

Stark JD, Vargas R, Banks JE (2007) Incorporating ecologicallyrelevant measures of pesticide effect for estimating the com-patibility of pesticides and biocontrol agents. Journal of Eco-nomic Entomology 100 (4): 1027–1032.

Stephens PA, Sutherland WJ (1999) Consequences of the Alleeeffect for behaviour, ecology and conservation. Trends inEcology and Evolution 14: 401–405.

Taneja SK, Sood V, Taneja S, Nath A (1979) effect of apholateon neurosecretion of pars intercerebralis, fat bodies, andovarian development of the red cotton cotton bug, Dysdercuskoenigii (F.). Indian Journal of Experimental Biology 17: 133–138.

Walthall WK, Stark JD (1996) A comparison of acute mortalityand population growth rate as endpoints of toxicologicaleffects. Ecotoxicology and Environmental Safety 37: 45–52.

Wang JJ, Cheng WX, Ding W, Zhao ZM (2004) The effect of theinsecticide dichlorvos on esterase activity extracted from thepsocids, Liposcelis bostrychophila and L. entomophila.Journal of Insect Science (Online) 4: 23–27.

Wennergren U, Stark JD (2000) Modeling long-term effects ofpesticides on populations: beyond just counting dead animals.Ecological Applications 10: 295–302.

Wilson TG, Cryan JR (1997) Lofenuron, a chitin synthesis inhibi-tor, interrupts development of Drosophila melanogaster. TheJournal of Experimental Zoology 278: 37–44.

Yin XH, Wu QJ, Li XF, Zhang YJ, Xu BY (2008a) Effect ofsub lethal concentrations of spinosad on the activities ofdetoxifying enzymes in the larvae of diamondback moth,Plutella xylostella. Chinese Journal of Pesticide Science 10:28–34.

Yin XH, Wu QJ, Li XF, Zhang YJ, Xu BY (2008b) Sub lethaleffects of spinosad on Plutella xylostella (Lepidoptera:Y-ponomeutidae). Crop Protection 27: 1385–1391.

Yin XH, Wu QJ, Li XF, Zhang YJ, Xu BY (2009) Demographicchanges in multigeneration Pultella xylostella (Lepidoptera:Plutellidae) after exposure to sub lethal concentration ofspinosad. Journal of Economic Entomology 102: 357–365.

M. S. Ansari et al.

338 Entomological Research 42 (2012) 330–338© 2012 The Authors. Entomological Research © 2012 The Entomological Society of Korea and Wiley Publishing Asia Pty Ltd