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Pak. Entomol. Vol. 32, No.2, 2010

163

PAKISTAN ENTOMOLOGIST

ISSN 1017-1827

http://www.pakentomol.com

email: [email protected]

EVALUATION OF INSECTICIDE RESISTANCE IN TWO STRAINS OF FRUIT FLY,BACTROCERA ZONATA (SAUNDERS) (TEPHRITIDAE: DIPTERA), WITH FRUIT DIP

METHOD

Syed Faisal Ahmad, Sohail Ahmed, Rashad Rasool Khan and Muhammad Kashif NadeemDepartment of Agri. Entomology, University of Agriculture, Faisalabad, Pakistan.

ABSTRACT

Present study was conducted to determine the level of insecticide resistance in five insecticides, viz., malathion,trichlorfon, lambda-cyhalothrin, spinosad and bifenthrin, commonly being used for the control of fruit flies, in

two field strains of fruit fly, Bactrocera zonata (Saunders) (Tephritidae: Diptera)by using fruit dip bioassay

method under laboratory conditions. Response data were collected at 24 and 48 hours after releasing gravedfemales in the cages having fruits dipped in appropriate concentrates of each insecticide. Results showed thatB.

zonata from Multan and Faisalabad zones were resistant to trichlorfon, malathion, lambda-cyhalothrin andbifenthrin ranging 3-19 fold, however, population from these places were susceptibility to spinosad. Malathion

registered resistances ratio (3-6 fold) less than bifenthrin (8-11 fold), trichlorofon (10-19 fold) and cyhalothrin(4-9 fold). The data suggest thatB. zonata has developed resistance to trichlorfon and indicate a danger for its

use as cover spray and in baits.

Keywords: Fruit fly,Bactrocera zonata, insecticide, resistance.

INTRODUCTION

About 11 species of fruit flies are recorded fromPakistan and most notable among them areBactocerazonata, B. cucurbitae, B. dorsalis, Myiopardalispardalina, Carpomiya incompleta, C. vesuviana,

Dacus ferrugincus and D. diversus (Abdullah andLatif, 2001; Abdullah et al., 2002; Stonehouse et al.,2002; Panhwar, 2005). The hosts of fruit fliesrecorded in Pakistan are apple, ber, guava, mango,musk melon and bitter gourd (Khan and Musakhel,

1999; Sultan et al., 2000; Ahmad et al., 2005).

Fruit flies rest on non-host plants which may or may

not sprayed. If not sprayed directly, these might haveresidues of insecticides by means of drifts from fields

where insecticides have been applied. The baitingwhich also includes insecticides is another source offruit flies succumbed to insecticide pressure. Thesetwo reasons are enough to justify speculation aboutinsecticide resistance in fruit flies. The topical

method of insecticide application was used to analyzethe resistance in laboratory bioassay which has been

a standardized method with Food and Agriculture

Organization (FAO) as well. Other methods of

application have received less attention and fruit dipis one of these methods (Hsu and Feng, 2000;Maklakov et al., 2001).

The extent of damage reported by the fruit fliesspecie, Bactrocera dorsalis was 5-100% loss inPakistan (Syed et al., 1970). Damage caused by fruitflies to fruit and vegetable growers in Pakistan isabout 200 million US dollars annually at farm level

with added losses to traders, retailers and exporters(Stonehouse et al., 1998). The greatest threat caused

by the fruit flies is the rejection of fruit commodity

especially mangoes due to presence of its maggotsand make it unfit for human consumption

(Stonehouse et al., 2002).

In Pakistan, the control of fruit flies is mainlydependent on the use of insecticides. Theseinsecticides have different methods of application

such as baiting, attractant insecticides and coversprays. The heavy infestation of fruit flies has lead to


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the use of cover sprays (Anonymous, 1986). Theinsecticides, for example, organophosphates,

carbamates, synthetic pyrethroids and new chemistryare being indiscriminately used by farmers as cover

sprays (Stonehouse et al., 1997; Alston, 2002;Ahmad et al., 2005; El-Aw et al., 2008). In this

paper, we have determined resistance in somepopulations ofB. zonata collected from Multan andFaisalabad and compared with a laboratory reared

population against bifenthrin (Talstar 10 EC),trichlorfon (Diptrex 80 SP), lambda-cyhalothrine(Karate 2.5 EC), Malathion (Fyfanon 57 EC) and

spinosad (Tracer 240 SC).

MATERIALS AND METHODS

Present study was conducted under laboratoryconditions (28

oC, 555% RH) in Department of Agri.

Entomology, University of Agriculture, Faisalabad todetermine the level of resistance against fiveinsecticides against fruit fly, B. zonata (Saunders)

commonly used for its control. Field populations ofB. zonata from Faisalabad and Multan zone werecollected from the infested and fallen fruits of themangoes and guava. A reference susceptible strainwas obtained from CABI, Multan in pupal form

which has been reared for the last many years withoutinsecticide exposure for comparison. The experimentwas laid down according to completely randomizeddesign with three replicates including an untreated

control. Rearing of both susceptible and field strainsofB. zonata were carried in Perspex cages on healthymango fruits for egg laying. The infested fruits werethen placed in a wooden cage having soil at the

bottom for pupation. The pupae were isolated fromthe soil and placed in a separate cage for emergence.

The adults were fed on banana based artificial diethaving ingredients such as egg yolk, sugar, honey,yeast, syrup vitamin B complex blended in the ratioof 2:4:8:2:2:1 respectively in an electric blender tomake a paste and was kept in a freezer for subsequent

use.

Commercial formulations of tested insecticides wereobtained from their manufacturers and were usedafter their dilutions in distilled water for the

determination of level of resistance against fieldpopulations ofB. zonata. 5-6 serial concentrations of

each insecticide were made to obtain most practicalconcentration that yielded mortality between 5-95%in each case. Fruit dip bioassay method was used to

expose both susceptible and field strains ofB. zonataagainst insecticides. Fresh mangoes were dipped in

the insecticide solution for 2-3 seconds and then wereair dried. Treated fruits were placed in the plastic jars

and equal numbers of 12-15 days old female adultswere transferred to each jar where they were also

provided with the normal adult diet. The openings ofthe plastic jars were covered with muslin cloth inorder to prevent escape of flies and also for proper

aeration. Irreversible knockdown followed by deathof the adult fruit flies was the criterion to determinemortality at the intervals of 24 and 48 hours.

Data for adult mortality were subjected to Probit

Analysis and was corrected by Abbotts formula(Abbott, 1925) and analyzed by Probit Analysis

(Finney, 1971) using the software POLO-PC (LeOraSoftware, 1987). The LC50 values of each compound

were estimated and compared with that of thelaboratory strain to determine the ratio of insecticideresistance.

RESULTS

Response ofB. zonata strains against bifenthrin

LC50 (ppm) of bifenthrin against Faisalabad

population was 458.62 at 24 hrs which was reducedto 247.77 after 48 hrs. In susceptible strain the valueof LC50 was found to be 55.79 and 25.2 ppm after 24and 48 hrs, respectively. Thus, Faisalabad strain

exhibited the resistance ratio of 8 folds after 24 hrswith an increase up to 9.8 folds after 48 hrs. InMultan strain, LC50 of bifenthrin was found to be533.33 and 279.28 ppm at 24 and 48 hrs,respectively, with the resistance ratio of 11 folds(Table 1).

Response ofB. zonata strains against trichlorfon

Faisalabad strain was found to be 10 and 13 foldsmore resistant as compared to the susceptible strainwith the LC50 (ppm) of 133.33 and 61.93 at 24 and 48

hr respectively in comparison to that of susceptible

strain 12.79 and 4.75 at 24 and 48 hrs, respectively(Table 2). Multan strain was found more resistant (6-9) to trichlorofon with the LC50 values of 214.45 and93.67 ppm at 24 and 48 hrs, respectively (Table 2).

Response ofB. zonata strains against malathion

LC50 (ppm) for Faisalabad strain, respectively, were60.81 and 24.96 ppm at 24 and 48 hrs (Table 3) withlow resistance ratio of 3 folds.


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Table 1. LC50 and Fit of Probit lines in strains ofB. zonata against bifenthrin.

StrainsObservation

(hrs )

LC50(ppm)

CI

(95%)

Fit of Probit line

SlopeSE 2

RR

24 55.79 39.16-91.63 1.410.27 0.38 -Laboratory

48 25.2 18.17-33.55 1.90.31 1.29 -24 458.62 305.89-852.04 1.210.26 0.22 8.22

Faisalabad 48 247.77 172.93-345 1.720.31 1.12 9.8324 533.33 367.8-950.23 1.380.27 0.90 9.55

Multan48 279.28 168.78-331.91 1.760.31 0.96 11.08

CI= Confidence interval; RR= Resistance ratio; LC50= Lethal concentration.

Table 2.-LC50 and Fit of Probit lines in strains ofB. zonata against trichlorfon.

StrainsObservation

(hrs )

LC50(ppm)

CI

(95%)

Fit of Probit line

SlopeSE 2

RR

24 12.79 8.86-21.11 1.340.27 0.52 -Laboratory

48 4.75 3.34-6.27 1.980.33 2.92 -

24 133.33 91.95-237.56 1.380.27 0.90 10.42

Faisalabad 48 61.93 42.86-86.83 1.680.31 0.91 13.0324 214.45 151.67-343.31 1.440.27 0.20 16.76

Multan48 93.67 64.84-127.33 1.730.30 0.84 19.72


Table 3. LC50 and Fit of Probit lines in various strains ofB. zonata against malathion.

StrainsObservation

(hrs )

LC50(ppm)

CI

(95%)

Fit of Probit line

SlopeSE 2

RR

24 16.66 11.49-29.69 1.380.27 0.90 -Laboratory

48 7.74 5.4-7.78 1.720.31 1.12 -24 60.81 41.94-106.4 1.350.27 0.17 3.65

Faisalabad 48 24.96 16.93-34.45 1.710.31 0.99 3.2224 91.68 64.35-142.98 1.40.27 0.10 5.50

Multan48 48.17 33.46-65.7 1.730.30 0.97 6.22


Table 4. LC50 and Fit of Probit lines in strains ofB. zonata against lambda-cyhalothrin.

StrainsObservation

(hrs )

LC50(ppm)

CI

(95%)

Fit of Probit Line

SlopeSE 2

RR

24 53.61 37.91-85.82 1.440.27 0.20 -Laboratory

48 17.49 7.72-28.38 2.000.33 3.36 -24 229.97 161.47-380.43 1.420.27 0.21 4.28

Faisalabad 48 84.91 61.88-110.1 2.280.37 1.99 4.8524 422.44 229.84-703.39 1.350.27 0.56 7.87

Multan48 162.13 113.84-214.50 1.420.27 2.87 9.26



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Table 5. LC50 and Fit of Probit lines in strains ofB. zonata against spinosad.

StrainsObservation

(hrs )

LC50(ppm)

CI

(95%)

Fit of Probit Line

SlopeSE 2

RR

24 53.61 37.91-85.82 1.440.27 0.20 -Laboratory

48 19.89 13.92-26.6 1.870.31 0.87 -24 41.73 28.85-65.02 1.350.26 0.23 0.77

Faisalabad 48 21.61 15.48-28.35 2.140.35 2.5 1.0824 87.45 59.46-141.86 1.280.26 0.76 1.63

Multan48 36.96 26.51-41.08 2.280.37 1.29 1.85


LC50 for the Multan strain was 91.68 ppm at 24 hrswhich was decreased to 48.17 ppm after 48 hrs of

exposure with resistance ratio of 5 and 6 fold,respectively.

Response ofB. zonata strains against lambda-

cyhalothrin

LC50 (ppm) for lambda-cyhalothrin was 53.61 and17.49 at 24 and 48 hrs with RR of 4 folds. LC50 of

422.44 (7 folds) and 162.13 (9 folds) ppm wasrecorded in Multan strain (Table 4).

Response ofB. zonata strains against spinosad

Both the field populations ofB. zonata were found

highly susceptible to spinosad (Table 5). After theexposure of 24 hrs, resistance ratio in Faisalabadstrain was found to be 0.77, which increased to 1.08

after 48 hrs presenting susceptibility with the LC50(ppm) of 41.73 and 21.61 after 24 and 48 hrs,

respectively, whereas, Multan strain exhibited theresistance ratio of 1 both after 24 and 48 hrs, and alsoshowed susceptibility towards spinosad with the LC50of 87.85 and 36.96 ppm in comparison to that ofsusceptible strain (53.61 and 19.89 ppm after 24 and

48 hrs, respectively).

DISCUSSION

From the results it is evident that both the field

strains exhibit varying ratios of insecticide resistanceagainst insecticides in the order of trichlorofon

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