evaluation of insecticide resistance in two strains of fruit fly ...

Pak. Entomol. Vol. 32, No.2, 2010
PAKISTAN ENTOMOLOGIST
ISSN 1017-1827
http://www.pakentomol.com
email: pakentoeditor@gmail.com
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 Nadeem
Department 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 graved
females in the cages having fruits dipped in appropriate concentrates of each insecticide. Results showed that B.
zonata from Multan and Faisalabad zones were resistant to trichlorfon, malathion, lambda-cyhalothrin and
bifenthrin 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 that B. 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 from
Pakistan and most notable among them are Bactocera
zonata, B. cucurbitae, B. dorsalis, Myiopardalis
pardalina, Carpomiya incompleta, C. vesuviana,
Dacus ferrugincus and D. diversus (Abdullah and
Latif, 2001; Abdullah et al., 2002; Stonehouse et al.,
2002; Panhwar, 2005). The hosts of fruit flies
recorded 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 have
residues of insecticides by means of drifts from fields
where insecticides have been applied. The baiting
which also includes insecticides is another source of
fruit flies succumbed to insecticide pressure. These
two reasons are enough to justify speculation about
insecticide resistance in fruit flies. The topical
method of insecticide application was used to analyze
the 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 dip
is one of these methods (Hsu and Feng, 2000;
Maklakov et al., 2001).
The extent of damage reported by the fruit flies
specie, Bactrocera dorsalis was 5-100% loss in
Pakistan (Syed et al., 1970). Damage caused by fruit
flies to fruit and vegetable growers in Pakistan is
about 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 maggots
and make it unfit for human consumption
(Stonehouse et al., 2002).
In Pakistan, the control of fruit flies is mainly
dependent on the use of insecticides. These
insecticides have different methods of application
such as baiting, attractant insecticides and cover
sprays. The heavy infestation of fruit flies has lead to
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Pak. Entomol. Vol. 32, No.2, 2010
the use of cover sprays (Anonymous, 1986). The
insecticides, for example, organophosphates,
carbamates, synthetic pyrethroids and new chemistry
are 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 some
populations of B. zonata collected from Multan and
Faisalabad 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 laboratory
conditions (28 o C, 55±5% RH) in Department of Agri.
Entomology, University of Agriculture, Faisalabad to
determine the level of resistance against five
insecticides against fruit fly, B. zonata (Saunders)
commonly used for its control. Field populations of
B. zonata from Faisalabad and Multan zone were
collected from the infested and fallen fruits of the
mangoes and guava. A reference susceptible strain
was obtained from CABI, Multan in pupal form
which has been reared for the last many years without
insecticide exposure for comparison. The experiment
was laid down according to completely randomized
design with three replicates including an untreated
control. Rearing of both susceptible and field strains
of B. zonata were carried in Perspex cages on healthy
mango fruits for egg laying. The infested fruits were
then placed in a wooden cage having soil at the
bottom for pupation. The pupae were isolated from
the soil and placed in a separate cage for emergence.
The adults were fed on banana based artificial diet
having ingredients such as egg yolk, sugar, honey,
yeast, syrup vitamin B complex blended in the ratio
of 2:4:8:2:2:1 respectively in an electric blender to
make a paste and was kept in a freezer for subsequent
use.
Commercial formulations of tested insecticides were
obtained from their manufacturers and were used
after their dilutions in distilled water for the
determination of level of resistance against field
populations of B. zonata. 5-6 serial concentrations of
each insecticide were made to obtain most practical
concentration that yielded mortality between 5-95%
in each case. Fruit dip bioassay method was used to
expose both susceptible and field strains of B. zonata
against insecticides. Fresh mangoes were dipped in
the insecticide solution for 2-3 seconds and then were
air dried. Treated fruits were placed in the plastic jars
and equal numbers of 12-15 days old female adults
were transferred to each jar where they were also
provided with the normal adult diet. The openings of
the plastic jars were covered with muslin cloth in
order to prevent escape of flies and also for proper
aeration. Irreversible knockdown followed by death
of the adult fruit flies was the criterion to determine
mortality at the intervals of 24 and 48 hours.
Data for adult mortality were subjected to Probit
Analysis and was corrected by Abbott’s formula
(Abbott, 1925) and analyzed by Probit Analysis
(Finney, 1971) using the software POLO-PC (LeOra
Software, 1987). The LC 50 values of each compound
were estimated and compared with that of the
laboratory strain to determine the ratio of insecticide
resistance.
RESULTS
Response of B. zonata strains against bifenthrin
LC 50 (ppm) of bifenthrin against Faisalabad
population was 458.62 at 24 hrs which was reduced
to 247.77 after 48 hrs. In susceptible strain the value
of LC 50 was found to be 55.79 and 25.2 ppm after 24
and 48 hrs, respectively. Thus, Faisalabad strain
exhibited the resistance ratio of 8 folds after 24 hrs
with an increase up to 9.8 folds after 48 hrs. In
Multan strain, LC 50 of bifenthrin was found to be
533.33 and 279.28 ppm at 24 and 48 hrs,
respectively, with the resistance ratio of 11 folds
(Table 1).
Response of B. zonata strains against trichlorfon
Faisalabad strain was found to be 10 and 13 folds
more resistant as compared to the susceptible strain
with the LC 50 (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 LC 50 values of 214.45 and
93.67 ppm at 24 and 48 hrs, respectively (Table 2).
Response of B. zonata strains against malathion
LC 50 (ppm) for Faisalabad strain, respectively, were
60.81 and 24.96 ppm at 24 and 48 hrs (Table 3) with
low resistance ratio of 3 folds.
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Pak. Entomol. Vol. 32, No.2, 2010
Table 1. LC 50 and Fit of Probit lines in strains of B. zonata against bifenthrin.
Strains
Observation LC 50
CI
Fit of Probit line
(hrs ) (ppm) (95%) Slope±SE λ 2 RR
Laboratory
24 55.79 39.16-91.63 1.41±0.27 0.38 -
48 25.2 18.17-33.55 1.9±0.31 1.29 -
Faisalabad
24 458.62 305.89-852.04 1.21±0.26 0.22 8.22
48 247.77 172.93-345 1.72±0.31 1.12 9.83
Multan
24 533.33 367.8-950.23 1.38±0.27 0.90 9.55
48 279.28 168.78-331.91 1.76±0.31 0.96 11.08
CI= Confidence interval; RR= Resistance ratio; LC 50 = Lethal concentration.
Table 2.-LC 50 and Fit of Probit lines in strains of B. zonata against trichlorfon.
Strains
Observation LC 50 CI
Fit of Probit line
(hrs ) (ppm) (95%) Slope±SE λ 2 RR
Laboratory
24 12.79 8.86-21.11 1.34±0.27 0.52 -
48 4.75 3.34-6.27 1.98±0.33 2.92 -
Faisalabad
24 133.33 91.95-237.56 1.38±0.27 0.90 10.42
48 61.93 42.86-86.83 1.68±0.31 0.91 13.03
Multan
24 214.45 151.67-343.31 1.44±0.27 0.20 16.76
48 93.67 64.84-127.33 1.73±0.30 0.84 19.72
CI= Confidence interval; RR= Resistance ratio; LC 50 = Lethal concentration.
Table 3. LC 50 and Fit of Probit lines in various strains of B. zonata against malathion.
Strains
Observation LC 50
CI
Fit of Probit line
(hrs ) (ppm) (95%) Slope±SE λ 2 RR
Laboratory
24 16.66 11.49-29.69 1.38±0.27 0.90 -
48 7.74 5.4-7.78 1.72±0.31 1.12 -
Faisalabad
24 60.81 41.94-106.4 1.35±0.27 0.17 3.65
48 24.96 16.93-34.45 1.71±0.31 0.99 3.22
Multan
24 91.68 64.35-142.98 1.4±0.27 0.10 5.50
48 48.17 33.46-65.7 1.73±0.30 0.97 6.22
CI= Confidence interval; RR= Resistance ratio; LC 50 = Lethal concentration.
Table 4. LC 50 and Fit of Probit lines in strains of B. zonata against lambda-cyhalothrin.
Strains
Observation LC 50
CI
Fit of Probit Line
(hrs ) (ppm) (95%) Slope±SE λ 2 RR
Laboratory
24 53.61 37.91-85.82 1.44±0.27 0.20 -
48 17.49 7.72-28.38 2.00±0.33 3.36 -
Faisalabad
24 229.97 161.47-380.43 1.42±0.27 0.21 4.28
48 84.91 61.88-110.1 2.28±0.37 1.99 4.85
Multan
24 422.44 229.84-703.39 1.35±0.27 0.56 7.87
48 162.13 113.84-214.50 1.42±0.27 2.87 9.26
CI= Confidence interval; RR= Resistance ratio; LC 50 = Lethal concentration.
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Pak. Entomol. Vol. 32, No.2, 2010
Table 5. LC 50 and Fit of Probit lines in strains of B. zonata against spinosad.
Strains
Observation LC 50 CI
Fit of Probit Line
(hrs ) (ppm) (95%) Slope±SE λ 2 RR
Laboratory
24 53.61 37.91-85.82 1.44±0.27 0.20 -
48 19.89 13.92-26.6 1.87±0.31 0.87 -
Faisalabad
24 41.73 28.85-65.02 1.35±0.26 0.23 0.77
48 21.61 15.48-28.35 2.14±0.35 2.5 1.08
Multan
24 87.45 59.46-141.86 1.28±0.26 0.76 1.63
48 36.96 26.51-41.08 2.28±0.37 1.29 1.85
CI= Confidence interval; RR= Resistance ratio; LC 50 = Lethal concentration.
LC 50 for the Multan strain was 91.68 ppm at 24 hrs
which was decreased to 48.17 ppm after 48 hrs of
exposure with resistance ratio of 5 and 6 fold,
respectively.
Response of B. zonata strains against lambdacyhalothrin
LC 50 (ppm) for lambda-cyhalothrin was 53.61 and
17.49 at 24 and 48 hrs with RR of 4 folds. LC 50 of
422.44 (7 folds) and 162.13 (9 folds) ppm was
recorded in Multan strain (Table 4).
Response of B. zonata strains against spinosad
Both the field populations of B. zonata were found
highly susceptible to spinosad (Table 5). After the
exposure of 24 hrs, resistance ratio in Faisalabad
strain was found to be 0.77, which increased to 1.08
after 48 hrs presenting susceptibility with the LC 50
(ppm) of 41.73 and 21.61 after 24 and 48 hrs,
respectively, whereas, Multan strain exhibited the
resistance ratio of 1 both after 24 and 48 hrs, and also
showed susceptibility towards spinosad with the LC 50
of 87.85 and 36.96 ppm in comparison to that of
susceptible 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 resistance
against insecticides in the order of trichlorofon <
bifenthrin < lambda-cyhalothrine < Malathion <
spinosad. Both the field strains showed high degree
of susceptibility towards spinosad. Hsu and Feng
(2000) assayed B. dorsalis adults and found
trichlorfon to be the least effective among the five
insecticides tested. Our results are also in line to that
of Kashyap and Hameed, 1982, but contradictory to
the findings of Raga and Sato (2006) who reported
trichlorofon as most effective against Ceratitis
capitata. Slope and λ 2 value (≤ 1-2) revealed
homogenous population of B. zonata being tested in
the present assay. Resistance to malathion in similar
species of fruit fly B. dorselis has been reported (Hsu
et al., 2004) and present results of resistance to
malathion also strengthen wide spread distribution of
its resistance. Magana et al. (2007) have shown
resistance to malathion in the field populations of
Ceratitis capitata. The cross resistance pattern can
also be witnessed in present study as populations
were resistant to trichlorfon and malathion and also
cyhalothrin and befintrhin, indicating two mechanism
of resistance operating in these populations. Elevated
hydrolytic and oxidative metabolic enzymes
combined altered AchE with poor catalytic efficiency
might contribute to resistance of B. dorsalis to
malathion (Hsu et al., 2004).
CONCLUSION
Further studies on populations of fruit flies in
different insecticides oriented farming systems will
help to understand the biochemical mechanism of
resistance. This study also suggests replacement of
trichlorfon with spinosad.
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