Potentiation/antagonism of deltamethrin and cypermethrins with organophosphate insecticides in the...

PESTICIDEBiochemistry & Physiology

Pesticide Biochemistry and Physiology 80 (2004) 31–42

www.elsevier.com/locate/ypest

Potentiation/antagonism of deltamethrin and cypermethrinswith organophosphate insecticides in the cotton bollworm,

Helicoverpa armigera (Lepidoptera: Noctuidae)

Mushtaq Ahmad

Central Cotton Research Institute, Multan, Pakistan

Received 19 January 2004; accepted 2 June 2004

Available online 15 July 2004

Abstract

The joint action of pyrethroids deltamethrin and cypermethrins in combination with organophosphates ethion,

profenofos, chlorpyrifos, quinalphos, and triazophos was studied on putatively resistant field populations of Heli-

coverpa armigera from Pakistan by using a leaf-dip method. Ethion produced a good potentiation with deltamethrin,

cypermethrin, alphacypermethrin, and zetacypermethrin, whereas profenofos, chlorpyrifos, quinalphos, and triazophos

exhibited an antagonism with deltamethrin as well as cypermethrins. Implications of using mixtures for counteracting

insecticide resistance are discussed.

� 2004 Elsevier Inc. All rights reserved.

Keywords: Helicoverpa armigera; Pakistan; Potentiation; Antagonism; Deltamethrin; Cypermethrin; Alphacypermethrin; Zetacyper-

methrin; Ethion; Profenofos; Chlorpyrifos; Quinalphos; Triazophos

1. Introduction

Insecticide mixtures are usually used in the field

to enhance the spectrum of control when multiple

pests are attacking simultaneously. They are alsorecommended to increase the efficacy of control

against a single pest, or to delay the development

of insecticide resistance or to combat current re-

sistance in a pest species. Using mixtures as a

countermeasure for resistance management in in-

sect pests has been advocated by several workers

[1–3] but without a good experimental evidence [4].

E-mail address: [email protected].

0048-3575/$ - see front matter � 2004 Elsevier Inc. All rights reserve

doi:10.1016/j.pestbp.2004.06.002

Mixtures are available as pre-mixes from the pes-

ticide companies or they are tank-mixed by the

farmers. Ideally, the insecticides having different

modes of action are mixed on the assumption that

they would complement the action of each otherfor killing the target pest.

In the present study, the term potentiation has

been used to indicate the enhanced toxic effect of

mixing two insecticidally active compounds in

comparison to synergism where the toxicity of an

insecticide is increased by the addition of an in-

secticidally non-toxic compound. When two com-

pounds are mixed, they can either be potentiatingor additive or antagonistic in an insect species.

d.

mail to: [email protected]

32 M. Ahmad / Pesticide Biochemistry and Physiology 80 (2004) 31–42

These effects can be different on different insectspecies or strains depending upon their physiology

and the mechanism(s) of resistance they have de-

veloped. If a mixture is potentiating, it is a useful

tool in enhancing control efficacy and combating

insecticide resistance. In this case, there may be

potential for reducing the application rate of one

or both components of the mixture. If a mixture is

antagonistic, it should not be used, because it willreduce the efficiency of pest control and aggravate

the resistance problem.

Because of their dissimilar modes of action,

pyrethroids and organophosphates (OPs) have

commonly been mixed since mid 1980s to manage

pest complex of cotton and other crops. The

present studies were undertaken to find out the

effect of mixing deltamethrin and cypermethrinswith OPs against field populations of cotton boll-

worm, Helicoverpa armigera (H€ubner) (Lepidop-

tera: Noctuidae), which developed resistance to

endosulfan, pyrethroids, organophosphates and

carbamates in Pakistan during 1990s [5–10].

2. Materials and methods

2.1. Insects

Fifth or sixth instar larvae of field populations

of H. armigera were collected from various loca-

tions in Pakistan. Each collection of about 400

larvae was made by walking through a 2-hectare

block of a particular host crop in a zigzag mannerto randomize collections. Cypermethrin + profe-

nofos mixture was also tested on a susceptible

laboratory strain obtained from the University of

Reading, UK. Larvae and adults were reared in

the laboratory on semi-synthetic diets as men-

tioned previously [5].

2.2. Insecticides

The commercial formulations of insecticidesused in bioassays were: Arrivo (cypermethrin,

100 g/L EC [emulsifiable concentrate]; FMC, Phil-

adelphia, PA, USA), Bestox (alphacypermethrin,

50 g/L EC; FMC), Fury (zetacypermethrin, 181 g/L

EC; FMC), Decis (deltamethrin, 25 g/L EC;

Aventis CropScience, Frankfurt, Germany), ethion(468 g/L EC; FMC), Curacron (profenofos, 500 g/L

EC; Syngenta, Basle, Switzerland), Lorsban

(chlorpyrifos, 400 g/L EC; Dow AgroSciences, In-

dianapolis, IN, USA), Ekalux (quinalphos, 250 g/L

EC; Syngenta) and Hostathion (triazophos, 400 g/

L EC; Aventis). The mixtures viz. Polytrin-C (cy-

permethrin, 40 g/L+profenofos, 400 g/L [1:10 ra-

tio] EC; Syngenta), Nurelle-D (cypermethrin, 50 g/L+ chlorpyrifos, 500 g/L [1:10] EC; Dow), Fury-F

(zetacypermethrin, 181 g/L+ ethion, 468 g/L [1:15]

EC; FMC), and Deltaphos (deltamethrin, 10 g/

L+ triazophos, 350 g/L [1:35] EC; Aventis) were

obtained as pre-mixes from the manufacturers and

rest of the mixtures were prepared by mixing in-

secticides in desired ratios just before treatment.

2.3. Bioassays

Newly moulted second instar larvae from F1

laboratory cultures were exposed to different in-

secticides using the leaf-dip method recommended

by the Insecticide Resistance Action Committee

(IRAC) [11]. Serial dilutions as ppm of the active

ingredient of the test compounds were prepared

using distilled water. Five-centimeter cotton

(Gossypium hirsutum) leaf discs were cut anddipped into the test solutions for 10 s with gentle

agitation, then allowed to dry on paper towel on

both sides. Five larvae were released on to each

leaf disc placed in a 5-cm-diameter petri dish with

adaxial side up. Eight replicates of five larvae were

used for each concentration and 6–11 serial con-

centrations were used for each test insecticide. The

same number of leaf discs per treatment wasdipped into distilled water as an untreated check.

Moistened filter papers were placed beneath leaf

discs to avoid desiccation of leaves in petri dishes.

After releasing the larvae, test containers were

covered with a piece of black cloth to minimize

cannibalism. Before and after the treatment, larvae

were maintained at a constant temperature of

25� 2 �C with a photo-period of 14 h.

2.4. Data analysis

Mortality was scored 48 h after the larvae

were placed on treated leaf discs. Larvae were

M. Ahmad / Pesticide Biochemistry and Physiology 80 (2004) 31–42 33

considered dead if they failed to make coordi-nated movements. Data were corrected for con-

trol mortality [12] and analyzed by probit

analysis [13] using the POLO-PC program [14].

Potency ratios (PRs) were determined by dividing

the estimated lethal concentration (LC) values of

the mixtures, calculated for similar joint action

according to Hoel [15], by the experimental LC

values observed in the bioassay. If PR¼ 1, themixture was considered having additive action; if

PR was <1, it showed an antagonistic action;

and if PR was >1, it exhibited a potentiating

action. The estimated LC value of a mixture of

A and B was computed as follows:

Estimated LCðAþ BÞ ¼ 1

lA=LCðAÞ þ lB=LCðBÞ;

where lA and lB represent the proportion of A andB in the mixture; lA þ lB ¼ 1.

3. Results

3.1. Deltamethrin

Deltamethrin showed a good potentiation withethion (PRs, 3–11) at a ratio of 1:10 on the three

populations tested (Table 1). After potentiation,

both LC50 and LC90 values for the mixture were

the same for Piplan and Bahawalpur populations.

Highest potentiation of the deltamethrin + ethion

mixture was produced in the Piplan population

(PRs, 10–11). By contrast, an antagonism was

observed when deltamethrin was mixed withprofenofos (1:10) or chlorpyrifos (1:10) or qui-

nalphos (1:10) or triazophos (1:35).

3.2. Cypermethrin

Like deltamethrin, cypermethrin + ethion (1:10)

produced a good to excellent potentiation in the

three populations of H. armigera tested (Table 2).

The Piplan population had the highest LC values

for cypermethrin and ethion and thus the highestresistance to both the insecticides. The potency

ratio of cypermethrin + ethion mixture was also

the highest in the Piplan population, 84 at LC50

and 74 at LC90; which reduced the LC values of

the mixture to the minimum, perhaps to the sus-ceptibility level. The LC values of the cypermeth-

rin + ethion mixture for Hasalpur and Bahawalpur

populations were similar but were about fivefold

higher than for Piplan population.

The mixtures of cypermethrin with profenofos

and chlorpyrifos were available in the market as

pre-mixes (1:10 ratios) for cotton pest control

in Pakistan. Cypermethrin +profenofos mixtureproduced an additive effect on the Reading strain,

which was a susceptible laboratory strain imported

from UK. On the other hand, this mixture showed

an antagonism in all the field populations tested.

The Vehari population was nearly susceptible for

both cypermethrin and profenofos and it exhibited

the lowest antagonism for the mixture. The Alipur

population was highly resistant to cypermethrin aswell as profenofos and it exhibited the highest

antagonism for the mixture. Cypermethrin mixed

with chlorpyrifos or quinalphos or triazophos in

the ratios of 1:10 also showed an antagonism in all

the populations tested.

3.3. Alphacypermethrin

Alphacypermethrin + ethion (1:10) mixture

produced a slight potentiation in Kabirwala andBahawalpur populations but a good potentiation

in the Piplan population (Table 3). Like ethion

mixtures with either deltamethrin or cypermethrin,

alphacypermethrin + ethion mixture showed the

highest potentiation in the Piplan population. The

LC values of alphacypermethrin for Piplan popu-

lation were 3–4 times higher than for Kabirwala

and Bahawalpur populations. The LC values ofalphacypermethrin + ethion were high but similar

for all the three populations tested. Similar to

deltamethrin and cypermethrin, mixtures of al-

phacypermethrin with either chlorpyrifos or tria-

zophos were antagonistic in H. armigera.

3.4. Zetacypermethrin

The zetacypermethrin + ethion mixture was

tested at two ratios, 1:10 and 1:15. It produced agood potentiation at both the ratios in all the se-

ven populations of H. armigera tested (Table 4).

The highest potentiation of this mixture was seen

Table 1

Potentiation/antagonism of deltamethrin with ethion, profenofos, chlorpyrifos, quinalphos, and triazophos in H. armigera

Colony Host Date tested Treatment No.

tested

Slope� SE LC50, ppm

(95% CL)

PR at

LC50

LC90, ppm

(95% CL)

PR at

LC90

Deltamethrin+ ethion

Kabirwala Cotton November 94 Deltamethrin 400 1.28� 0.11 14.3 (10.9–18.8) — 143 (91.7–223) —

Ethion 400 1.29� 0.11 2184 (1669–2857) — 21499 (13,302–34,746) —

Deltamethrin + ethion (1:10) 280 2.21� 0.21 44.1 (36.1–53.8) 3.3 167 (121–231) 8.8

Piplan Chickpea March 95 Deltamethrin 360 1.72� 0.15 16.3 (13.0–20.4) — 90.2 (62.6–130) —

Ethion 320 1.70� 0.16 699 (555–880) — 3955 (2690–5816) —

Deltamethrin + ethion (1:10) 320 1.83� 0.17 14.0 (11.2–17.4) 10 70.1 (49.0–100) 11

Bahawalpur Squash March 97 Deltamethrin 320 1.95� 0.18 12.4 (10.1–15.4) — 56.3 (39.9–79.5) —

Ethion 320 1.87� 0.17 154 (124–192) — 749 (528-1064) —

Deltamethrin + ethion (1:10) 320 1.81� 0.16 14.9 (11.9–18.5) 5.1 75.9 (52.8–109) 4.7

Deltamethrin+ profenofos

Khanpur Cotton October 96 Deltamethrin 280 1.73� 0.20 30.1 (22.0–39.8) — 166 (115–280) —

Profenofos 280 2.28� 0.28 14.5 (11.1–18.3) — 52.9 (39.8–78.7) —

Deltamethrin + profenofos (1:10) 240 2.12� 0.27 27.0 (20.1–34.7) 0.56 108 (79.1–172) 0.52

Multan-2 Cotton October 98 Deltamethrin 240 2.19� 0.27 68.2 (52.5–85.9) — 262 (195–403) —

Profenofos 320 1.43� 0.17 9.60 (6.49–13.4) — 75.1 (49.5–136) —

Deltamethrin + profenofos (1:10) 240 2.11� 0.26 31.5 (24.2–40.0) 0.33 127 (92.4–202) 0.63

Deltamethrin+ chlorpyrifos

Khanpur Cotton October 96 Chlorpyrifos 320 1.58� 0.18 11.2 (8.03–15.0) — 72.1 (49.3–123) —

Deltamethrin + chlorpyrifos (1:10) 280 1.83� 0.20 16.3 (12.4–21.0) 0.73 82.1 (58.9–131) 0.93

Multan-2 Cotton October 98 Chlorpyrifos 280 2.17� 0.24 7.77 (6.09–9.73) — 30.2 (22.5–45.4) —

Deltamethrin + chlorpyrifos (1:10) 240 2.27� 0.29 12.3 (9.22–15.7) 0.69 45.2 (33.7–69.3) 0.73

Deltamethrin+ quinalphos

Hasalpur Okra July 93 Deltamethrin 320 1.49� 0.14 18.3 (14.1–23.6) — 133 (90.7–225) —

Quinalphos 320 1.71� 0.18 4.20 (3.10–5.51) — 23.7 (16.8–23.7) —

Deltamethrin + quinalphos (1:10) 240 2.63� 0.34 20.6 (15.8–25.6) 0.22 63.2 (48.7–91.5) 0.41

Multan-2 Cotton October 98 Quinalphos 240 2.06� 0.25 8.17 (6.20–10.4) — 34.2 (25.0–54.1) —

Deltamethrin + quinalphos (1:10) 240 2.14� 0.29 23.0 (16.6–29.9) 0.39 91.5 (67.1–144) 0.41

Deltamethrin+ triazophos

Okara Squash April 93 Deltamethrin 280 2.60� 0.26 6.86 (5.72–8.22) — 21.3 (16.1–28.3) —

Triazophos 320 1.86� 0.17 50.0 (40.2–62.1) — 244 (171–350) —

Deltamethrin + triazophos (1:35) 280 2.59� 0.25 70.1 (58.4–84.0) 0.61 219 (165–291) 0.86

Shershah Cotton September 95 Deltamethrin 360 1.62� 0.14 3.35 (2.65–4.24) — 20.6 (14.1–30.2) —

Triazophos 360 1.47� 0.13 15.0 (11.7–19.2) — 111 (73.1–169) —

Deltamethrin + triazophos (1:35) 360 1.52� 0.13 46.7 (36.6–59.7) 0.29 326 (218–485) 0.31

Alipur Cotton September 99 Deltamethrin 320 1.76� 0.16 36.1 (28.8–45.2) — 192 (133–277) —

Triazophos 360 1.65� 0.14 260 (207–328) — 1549 (1061–2261) —

Deltamethrin + triazophos (1:35) 360 1.59� 0.14 246 (194–311) 0.90 1570 (1063–2319) 0.82

Shujabad Cotton September 00 Deltamethrin 280 2.12� 0.22 65.0 (47.8–87.5) — 261 (178–472) —

Triazophos 280 1.81� 0.20 116 (89.1–149) — 592 (422–953) —

Deltamethrin + triazophos (1:35) 360 1.70� 0.16 494 (373–641) 0.23 2806 (2006–4371) 0.20

34

M.Ahmad/Pesticid

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Table 2

Potentiation/antagonism of cypermethrin with ethion, profenofos, chlorpyrifos, quinalphos, and triazophos in H. armigera


tested

Slope�SE LC50, ppm

(95% CL)

PR at

LC50

LC90, ppm

(95% CL)

PR at

LC90

Cypermethrin+ ethion

Hasalpur Okra July 93 Cypermethrin 360 1.81� 0.15 28.0 (22.5–34.8) — 143 (101–202) —

Ethion 440 0.90� 0.08 589 (418–831) — 15520 (8356–28,824) —

Cypermethrin+ ethion (1:10) 320 1.90� 0.17 26.7 (21.5–33.1) 7.8 126 (89.3–178) 11

Piplan Chickpea March 95 Cypermethrin 320 1.82� 0.17 109 (87.6–136) — 553 (382–802) —

Ethion 320 1.70� 0.16 699 (555–880) — 3955 (2690–5816) —

Cypermethrin+ ethion (1:10) 360 1.63� 0.14 5.59 (4.43–7.05) 84 34.1 (23.2–49.9) 74

Bahawalpur Squash March 97 Cypermethrin 320 1.79� 0.16 50.4 (40.3–63.0) — 263 (181–382) —

Ethion 320 1.87� 0.17 154 (124–192) — 749 (528–1064) —

Cypermethrin+ ethion (1:10) 320 1.80� 0.16 31.9 (25.5–39.8) 4.1 164 (113–236) 3.9

Cypermethrin+ profenofos

Reading Art. diet November 93 Cypermethrin 280 2.80� 0.28 0.52 (0.44–0.62) — 1.50 (1.15–1.97) —

Profenofos 240 3.96� 0.46 1.73 (1.50–2.00) — 3.64 (2.91–4.56) —

Cypermethrin+profenofos (1:10) 280 3.02� 0.31 1.43 (1.21–1.69) 1.0 3.79 (2.92–4.92) 0.85

Vehari Okra July 91 Cypermethrin 440 1.15� 0.09 0.74 (0.56–0.99) — 9.72 (6.02–15.7) —

Profenofos 400 1.37� 0.12 2.84 (2.19–3.69) — 24.5 (16.2–37.1) —

Cypermethrin+profenofos (1:10) 400 1.47� 0.12 3.58 (2.80–4.58) 0.63 26.5 (17.9–39.3) 0.81

R.Y.Khan Cotton October 91 Cypermethrin 280 2.55� 0.25 87.1 (72.4–105) — 277 (206–372) —

Profenofos 320 1.62� 0.15 3.60 (2.83–4.56) — 22.2 (14.6–33.8) —

Cypermethrin+profenofos (1:10) 360 1.49� 0.13 13.3 (10.3–17.0) 0.30 96.3 (61.7–150) 0.25

Multan-1 Cotton October 91 Cypermethrin 440 1.05� 0.09 14.9 (11.0–20.2) — 247 (144–422) —

Profenofos 320 1.98� 0.18 2.70 (2.19–3.33) — 12.0 (8.55–16.7) —

Cypermethrin+profenofos (1:10) 360 1.69� 0.15 12.4 (9.85–15.6) 0.24 71.3 (48.4–105) 0.18

Bhakkar-1 Cotton October 91 Cypermethrin 400 1.37� 0.11 39.4 (30.4–51.1) — 388 (214–534) —

Profenofos 360 1.53� 0.13 4.93 (3.86–6.28) — 33.9 (22.4–51.3) —

Cypermethrin+profenofos (1:10) 400 1.34� 0.11 19.0 (14.6–24.7) 0.28 172 (108–274) 0.22

Alipur Cotton September 99 Cypermethrin 240 3.04� 0.32 150 (126–177) 394 (304–512)

Profenofos 280 2.27� 0.22 17.2 (14.1–20.9) 63.0 (46.0–86.5)

Cypermethrin+profenofos (1:10) 320 1.59� 0.15 92.0 (72.3–117) 0.20 589 (388–893) 0.12

Cypermethrin+ chlorpyrifos

Kabirwala Cotton November 94 Cypermethrin 280 2.61� 0.26 17.7 (14.8–21.2) — 54.9 (41.3–73.0) —

Chlorpyrifos 240 3.32� 0.37 4.45 (3.79–5.23) — 18.8 (8.37–14.0) —

Cypermethrin+ chlorpyrifos (1:10) 240 3.49� 0.39 7.95 (6.80–9.30) 0.60 18.5 (14.5–23.6) 0.63

Lar Cotton October 95 Cypermethrin 280 2.32� 0.23 152 (125–184) — 540 (395–739) —

Chlorpyrifos 240 2.68� 0.28 2.50 (2.09–3.00) — 7.53 (5.66–10.0) —

Cypermethrin+ chlorpyrifos (1:10) 280 2.48� 0.24 4.47 (3.71–5.39) 0.61 14.7 (10.9–19.7) 0.56

M.Ahmad/Pesticid

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35

Table

2(continued)

Colony

Host

Date

tested

Treatm

ent

No.

tested

Slope�SE

LC

50,ppm

(95%

CL)

PR

at

LC

50

LC

90,ppm

(95%

CL)

PR

at

LC

90

Cypermethrin+quinalphos

Multan-2

Cotton

October

98

Cypermethrin

280

1.95�0.26

109(76.7–144)

—496(358–796)

—

Cypermethrin+quinalphos(1:10)

240

2.24�0.30

49.7

(36.7–63.7)

0.18

185(137–286)

0.20

Cypermethrin+triazophos

Khanew

al

Okra

June99

Cypermethrin

320

1.91�0.19

215(167–274)

—1012(735–1561)

—

Triazophos

320

1.99�0.21

52.3

(40.1–66.6)

—230(169–352)

—

Cypermethrin+triazophos(1:10)

320

1.93�0.20

262(203–333)

0.21

1204(880–1840)

0.21

Lahore

Okra

June00

Cypermethrin

320

1.68�0.17

94.5

(61.7–140)

—548(331–1228)

—

Triazophos

320

1.84�0.18

21.5

(16.6–27.5)

—107(77.4–165)

—

Cypermethrin+triazophos(1:10)

320

1.85�0.18

175(138–222)

0.13

865(620–1361)

0.13


in the Alipur population (22-fold at LC50 and 16-fold at LC90), which had the highest LC50 values

for both zetacypermethrin and ethion. However,

when zetacypermethrin was mixed with either

profenofos or chlorpyrifos or quinalphos, an an-

tagonism was observed in the Pakistani popula-

tions of H. armigera.

The above results demonstrate that deltameth-

rin as well as three cypermethrins exhibited a goodpotentiation with ethion, which could be exploited

in counteracting resistance in H. armigera. The

mixture of zetacypermethrin + ethion (1:15), called

Fury-F, has successfully been used against cotton

bollworms in Pakistan and Australia.

4. Discussion

One of the pathways of pyrethroid detoxifica-

tion in insects is due to the action of pyrethroid-

hydrolyzing esterases [16–20], which metabolize

and possibly sequester the pyrethroid insecticides.

Overproduction of esterase isozymes is often in-

volved in pyrethroid resistance in many pests

[21,22]. Pyrethroid-resistant H. armigera possessedan enhanced esterase activity in Australia [23],

India [24], and Pakistan (Ahmad M, unpublished

data).

Biochemical studies have shown that pyre-

throid resistance-associated esterases in H. armi-

gera are inhibited by organophosphorus

compounds, such as ethion, profenofos, chlor-

pyrifos, and acephate [25]; and that OPs bind tothe active site of the enzyme, thus preventing

pyrethroid detoxification. In the present study,

only ethion was potentiating with the pyrethroids

in the resistant field populations of H. armigera

tested, and profenofos, chlorpyrifos, quinalphos

and triazophos were rather antagonistic (Tables

1–4). This antagonism between pyrethroids and

OPs is not understood. Inhibition of esterase ac-tivity by ethion was found to be much prolonged

(up to 48 h) compared to profenofos and chlor-

pyrifos (up to 10 h) [25]. Ethion was also poten-

tiating with cypermethrin in H. armigera in West

Africa [26] and with deltamethrin in cattle tick

Boophilus microplus (Can.) in Australia [27].

Ethion has an additional benefit of mite control

Table 3

Potentiation/antagonism of alphacypermethrin with ethion, chlorpyrifos, and triazophos in H. armigera


tested


(95% CL)

PR at

LC50

LC90, ppm

(95% CL)

PR at

LC90

Alphacypermethrin+ ethion

Kabirwala Cotton November 94 Alphacypermethrin 360 1.37� 0.12 8.59 (6.62–11.2) — 74.1 (46.8–117) —

Ethion 400 1.29� 0.11 2184 (1669–2857) — 21499 (13,302–34,746) —


(1:10)

320 1.89� 0.17 65.8 (53.0–81.7) 1.4 315 (221–448) 2.5

Piplan Chickpea March 95 Alphacypermethrin 320 1.80� 0.16 37.4 (30.0–46.8) — 192 (134–275) —

Ethion 320 1.70� 0.16 699 (555–880) — 3955 (2690–5816) —


(1.10)

320 1.91� 0.17 75.5 (60.9–93.6) 3.5 355 (249–506) 4.0

Bahawalpur Squash March 97 Alphacypermethrin 360 1.44� 0.13 13.2 (10.2–16.9) — 101 (66.5–155) —

Ethion 320 1.87� 0.17 154 (124–192) — 749 (528–1064) —


(1:10)

320 1.70� 0.16 57.2 (45.4–72.1) 1.4 325 (221–477) 1.5

Alphacypermethrin+ chlorpyrifos

Lar Cotton October 95 Alphacypermethrin 280 2.41� 0.23 31.6 (26.2–38.2) — 107 (79.6–145) —

Chlorpyrifos 240 2.68� 0.28 2.50 (2.09–3.00) — 7.53 (5.66–10.0) —


(1:10)

280 2.18� 0.21 11.0 (8.98–13.4) 0.25 42.4 (30.6–58.6) 0.19

Khanewal Okra June 99 Alphacypermethrin 280 2.43� 0.28 86.9 (60.3–121) — 293 (197–588) —

Chlorpyrifos 320 1.94� 0.20 5.84 (4.53–7.42) — 26.7 (19.5–40.7) —


(1:10)

280 2.16� 0.25 17.5 (13.2–22.3) 0.36 68.5 (51.0–103) 0.43

Alphacypermethrin+ triazophos

Multan-2 Cotton October 98 Alphacypermethrin 320 1.46� 0.14 101 (77.7–131) — 757 (504–1330) —

Triazophos 320 1.77� 0.19 49.0 (36.6–63.8) — 260 (185–417) —


(1:10)

280 2.34� 0.23 184 (151–224) 0.28 650 (495–944) 0.43

Lahore Okra June 00 Alphacypermethrin 360 1.54� 0.14 65.7 (50.1–85.3) — 447 (311–727) —


(1:10)

360 1.53� 0.14 217 (164–283) 0.11 1495 (1029–2459) 0.08

M.Ahmad/Pesticid

eBiochem

istryandPhysio

logy80(2004)31–42

37

Table 4

Potentiation/antagonism of zetacypermethrin with ethion, profenofos, chlorpyrifos, and quinalphos in H. armigera


tested


(95% CL)

PR at

LC50

LC90, ppm

(95% CL)

PR at

LC90

Zetacypermethrin+ ethion

Faisalabad Cauliflower December 92 Zetacypermethrin 280 2.41� 0.24 2.77 (2.29–3.34) — 9.40 (7.00–12.6) —

Ethion 360 1.63� 0.14 645 (511–815) — 3953 (2673–5847) —

Zetacypermethrin+ ethion (1:10) 320 1.82� 0.17 6.44 (5.16–8.04) 4.5 32.6 (22.8–46.7) 3.1

Bhakkar-2 Chickpea March 94 Zetacypermethrin 280 2.06� 0.20 1.91 (1.55–2.35) — 8.00 (5.69–11.3) —

Ethion 320 1.83� 0.17 21.6 (17.3–26.9) — 108 (75.4–155) —


Shershah Cotton September 95 Zetacypermethrin 280 2.09� 0.20 38.9 (31.6–47.8) — 159 (113–225) —

Ethion 360 1.52� 0.13 1181 (926–1507) — 8223 (5431–12449) —

Zetacypermethrin+ ethion (1:15) 200 3.48� 0.40 116 (98.8–135) 3.6 270 (211–345) 7.3

Depalpur Cotton November 95 Zetacypermethrin 320 1.95� 0.18 2.68 (2.17–3.31) — 12.2 (8.69–17.2) —

Ethion 280 2.11� 0.20 2118 (1726–2598) — 8576 (6128–12003) —


Sheikhupura Pea January 97 Zetacypermethrin 280 2.26� 0.22 7.10 (5.83–8.64) — 26.3 (19.2–35.9) —

Ethion 320 1.99� 0.18 793 (644–978) — 3484 (2486–4883) —


Multan-2 Cotton October 98 Zetacypermethrin 320 2.06� 0.19 20.8 (16.9–25.5) — 87.3 (63.0–121) —

Ethion 240 2.66� 0.28 893 (745–1070) — 2702 (2009–3635) —

Zetacypermethrin+ ethion (1:15) 240 2.63� 0.27 51.0 (42.5–61.2) 4.8 157 (117–211) 6.0

Alipur Cotton September 99 Zetacypermethrin 320 1.72� 0.16 42.7 (34.0–53.7) — 237 (162–346) —

Ethion 240 3.26� 0.35 2573 (2189–3025) — 6355 (4950–8157) —

Zetacypermethrin+ ethion (1:15) 320 1.63� 0.15 24.3 (19.2–30.8) 22 149 (99.1–225) 16

Zetacypermethrin+ profenofos

Sahiwal Potato December 91 Zetacypermethrin 320 1.92� 0.17 0.39 (0.32–0.48) — 1.81 (1.28–2.56) —

Profenofos 360 1.76� 0.16 15.6 (12.4–19.5) — 83.4 (56.8–122) —

Zetacypermethrin+profenofos

(1:10)

320 1.93� 0.18 22.3 (18.0–27.6) 0.15 103 (72.0–1475) 0.16

Khanewal Okra June 99 Zetacypermethrin 320 1.84� 0.18 106 (75.0–147) — 528 (346–995) —

Profenofos 320 1.90� 0.19 6.15 (4.40–8.43) — 29.0 (19.4–53.0) —

Zetacypermethrin+profenofos

(1:10)

280 2.10� 0.25 37.6 (28.4–48.0) 0.18 153 (113–234) 0.21

Zetacypermethrin+ chlorpyrifos

Sahiwal Potato December 91 Chlorpyrifos 320 2.25� 0.21 1.82 (1.49–2.21) — 6.75 (4.95–9.21) —


(1:10)

320 1.90� 0.17 4.76 (3.83–5.90) 0.29 22.6 (15.8–32.2) 0.24

Lodhran Cotton September 92 Zetacypermethrin 360 1.72� 0.15 3.50 (2.79–4.39) — 19.6 (13.6–28.1) —

Chlorpyrifos 360 1.64� 0.14 4.86 (3.85–6.13) — 29.5 (20.0–43.5) —


(1:10)

360 1.82� 0.16 6.89 (5.53–8.57) 0.68 35.0 (24.5–49.9) 0.80

38

M.Ahmad/Pesticid

eBiochem

istryandPhysio

logy80(2004)31–42

Zetacypermethrin+quinalphos

Sahiwal

Potato

Decem

ber

91

Quinalphos

280

2.69�0.27

12.2

(10.2–14.6)

—36.6

(27.8–48.2)

—


(1:10)

320

2.17�0.20

8.44(6.92–10.3)

0.37

33.0

(24.0–45.2)

0.40

Bahawalpur

Squash

March97

Zetacypermethrin

240

2.08�0.23

38.1

(30.8–47.1)

—157(110–224)

—

Quinalphos

240

2.51�0.26

10.0

(8.32–12.1)

—32.6

(24.1–44.0)

—


(1:10)

240

1.84�0.21

20.2

(16.0–25.7)

0.53

101(67.9–149)

0.35


and therefore pyrethroid + ethion mixtures makesense for both insect and mite control. Ethion is a

dithioate organophosphate whereas profenofos,

chlorpyrifos, quinalphos, and triazophos are mo-

nothioate organophosphates.

Synergism of pyrethroids with profenofos, pre-

sumably due to the inhibition of esterases, has

been documented in H. armigera [20,28], tobacco

budworm Heliothis virescens (F.) [29], pink boll-worm Pectinophora gossypiella Saund. [30], cab-

bage looper Trichoplusia ni (H€ubner) [18], cottonleafworm Spodoptera littoralis (Boisd.) [2], and

cotton whitefly Bemisia tabaci (Genn.) [19,31]. The

cypermethrin +profenofos mixture provided a

synergistic effect on the susceptible strain of H.

armigera from West Africa but an additive effect

on the resistant strain [26]. By contrast, profenofosfailed to synergize pyrethroids in H. armigera in

Australia [32] and flour beetle Tribolium castaneum

(Herbst) in Israel [33]. The esterase activity was

not significantly correlated with profenofos syn-

ergism of pyrethroids in the Indian H. armigera

[24]. In the present study, profenofos was additive

with cypermethrin in the susceptible Reading

strain of H. armigera but highly antagonistic inthe Pakistani field populations (Table 2). Accord-

ing to Kranthi et al. [24], profenofos similarly

had no synergism with cypermethrin in the sus-

ceptible Reading strain but contrarily it produced

synergism in the Indian field populations of

H. armigera.

In the present study, chlorpyrifos exhibited

antagonism with deltamethrin and cypermethrinsin H. armigera (Tables 1–4). Similarly, chlorpyri-

fos did not show potentiation with cypermethrin

[34], cyfluthrin or betacyfluthrin [26] in the West

African populations of H. armigera. There was

also no chlorpyrifos potentiation of cypermethrin

and fenvalerate in S. littoralis [35]. However, del-

tamethrin+ chlorpyrifos mixture produced an ad-

ditive effect on the susceptible strain but asynergistic effect on the resistant strain of H.

armigera [26]. Chlorpyrifos also showed a poten-

tiation with fenvalerate in the two-spotted spider

mite Tetranychus urticae Koch in New Zealand

[36]. The magnitude of synergism appeared to

depend on the species, organophosphorus com-

pound and pyrethroid involved [37].


Quinalphos and triazophos were both antag-onistic with deltamethrin, cypermethrin, alpha-

cypermethrin, and zetacypermethrin in all

Pakistani populations of H. armigera tested.

Contrarily, deltamethrin + triazophos mixture

showed a good potentiation in H. armigera in

West Africa [26].

Based on the theory that pyrethroids are syn-

ergized by OPs by inhibiting pyrethroid hydro-lyzing esterases, many pesticide companies

introduced OP+pyrethroid mixtures to control

multi-pest situations and counteract resistance. In

Pakistan, pre-mixes of cypermethrin with profe-

nofos or chlorpyrifos, and of deltamethrin with

triazophos were introduced soon after the com-

mercial launch of pyrethroids. Such pre- and tank-

mixes proved successful initially until resistanceoccurred to one or both the mixing partners. Since

most of the mixtures were not potentiating, as the

present studies indicate; their early success might

be due to broadening the spectrum of control

against the pest complexes of many crops in Pa-

kistan but not due to delaying or preventing re-

sistance. Many insects like H. armigera are

particularly notorious in developing multiplemechanisms of resistance [38].

For resistance management, even potentiating

mixtures have the limitations. They can hardly

suppress one metabolic mechanism such as de-

toxification by esterases in the case of OP+py-

rethroid mixtures. When that mechanism is

suppressed, other mechanisms are selected, which

are then insensitive to both partners of the mix-ture. Mixtures give rise to multiple resistance that

may extend across other chemical classes and

that is difficult to manage. Mixtures as tools of

resistance management may be a good strategy in

the short run but does not seem to be a good

option in the long run. However, potentiating

mixtures may be a good solution to control

multi-pest situations with least cost and combatresistance when it is still low. A potentiating

mixture for one insect may not be so for another.

Consequent effect of a mixture may be deter-

mined by the physiology of an insect species, its

metabolic pathways for a particular insecticide(s)

and the mechanisms of resistance present in a

resistant pest.

The use of potentiating mixtures can reduce thecrop protection costs by the lesser amounts of

active ingredients used, the labour costs by the

lesser number of spray applications and the impact

on the environment and non-target organisms.

Additive mixtures can be used when absolutely

necessary because they do not give much added

benefit. Antagonistic mixtures should never be

used because they exacerbate the problem by notcontrolling the target pests, by increasing the ap-

plication rates of pesticides and having adverse

environmental effects.

Before recommending mixtures, studies should

be carried out to determine if a particular mixture is

potentiating, additive or antagonistic against the

target and non-target pests. It should also be found

in which ratio a particular mixture can give the bestpotentiation. What are the mechanisms of poten-

tiation/antagonism of a mixture? What will be the

environmental fate of the mixture, its joint action

on humans, animals, birds, and aquatic life? Simi-

lar toxicological data as for individual insecticides

should be generated for the mixture. Pest control

with mixtures as with individual insecticides must

be integrated with non-chemical pest managementtactics to avoid impending problems for the future.

Acknowledgments

The technical assistance of M. Iqbal Arif,

Tanveer Hussain, Tabassam Nurin, and Hina

Rana is much appreciated.

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