incidence and mechanisms of resistance in bemisia tabaci ... 2006 q-b… · 874 rf rauch &...

St. Louis – Bemisia tabaci, Q-biotype Symposium – April 3, 2006

Incidence and mechanisms Incidence and mechanisms of resistance in of resistance in Bemisia tabaciBemisia tabaci with with special reference to biotype Qspecial reference to biotype Q

R. Nauen, J. Benting, A. Elbert, D. Rogers, and I. Denholm*Bayer CropScience AG, Research Insecticides, Monheim, Germany*Rothamsted Research, Harpenden, UK


Bemisia tabaci(sweetpotato whitefly)

Q-type B-type

Esterase banding pattern to differentiate biotypes

Two important biotypes are B- and Q-types. Themost dominant biotype world-wide is B, whereasQ is to a greater or lesser extent restricted to the Mediterranean basin (e.g. Almeria Spain).

Two important biotypes of Bemisia tabaci


Resistance monitoring in Almeria, Spain

0

20

40

60

80

100

SUD-S ALM-2 ESP-6 ESP-98 ESP2-99

Mor

talit

y, %

Imidacloprid Thiamethoxam Acetamiprid16 ppm

1994

1996

1998 1999

Almeria, Spain

Nauen et al. (2002) Pest. Manag. Sci. 58


Bemisia tabaci

Spread of neonicotinoid resistance andQ-biotypes in the Mediterranean basin


Biochemistry of neonicotinoid resistance

Target site insensitivityResistance enzyme levels

EsterasesGlutathione S-transferasesMonooxygenases

SynergismMetabolism in vivo

Bemisia tabaci


Target site insensitivityResistance enzyme levels

EsterasesGST´sMonooxygenases

SynergismMetabolism in vivo

-12 -11 -10 -9 -8 -7 -6 -50

102030405060708090

100 SUD-S

IT-99ESP-00

GER-01USA-BISR-02

E99-2

log[Imidacloprid], M

% T

otal

bin

ding

0

100

200

300

400

500

600

SU

D-S

US

A-B

ALM

-99

IT-9

9

ES

P-0

0

GE

R-0

1

VE

N-0

2

ISR

-02

fluor

esce

nce/

20 m

in/µ

g pr

otei

n

0

10

20

30

40

SU

D-S

US

A-B

E99

-2

IT-9

9

ES

P-0

0

GE

R-0

1

VE

N-0

2

ISR

-02

mO

D/m

in/µ

g pr

otei

n

1-NA1-NB

Biochemistry of imidacloprid resistance in whiteflies (negative systems)

EsterasesGlutathione S-transferases

Receptor binding

Rauch & Nauen (2003) Arch Insect Biochem Physiol. 54

Bemisia tabaci


Monooxygenases confer neonicotinoidresistance in Bemisia tabaci

0

200

400

600

800

1000

SU

D-S

US

A-B

E99

-2

IT-9

9

ES

P-0

0

GE

R-0

1

VE

N-0

2

ISR

-02

pmol

/30m

in/m

g pr

otei

n

OH5C2O O OOH O+ CH3 CHO

NADPH+H+, O2

OH2-

7-Ethoxycoumarin-O-deethylase activity is a biochemical marker linked to neonicotinoid resistance in Bemisia tabaci

1 233 22

> 1000

11

874 RF

Rauch & Nauen (2003) Arch. Insect Biochem. Physiol. 54

Bemisia tabaci


Elevated Cyt P-450 activity confers neonicotinoidcross resistance

N NH

NCl NNO2

N N

O

S

NCl

N

CH3

NO2

CH3

N

NCl NCN

CH3

0

200

400

600

800

0,1 1 10 100 1000

LC thiamethoxam, ppm 50

pmol

/30m

in/m

g pr

otei

n R2 = 0.82

0

200

400

600

800

0,1 1 10 100 1000LC acetamiprid, ppm 50

pmol

/30m

in/m

g pr

otei

n R2 = 0.75

0

200

400

600

800

0,1 1 10 100 1000

LC imidacloprid, ppm50

pmol

/30m

in/m

g pr

otei

n R2 = 0.89


020406080

100

16ppm 4ppm

Morta

lity,

%

Imidacloprid Imi + PB Imi + PPP

[Imi, conc.]

2d

+ 1000 ppm PB + 16 ppm IMI

Synergism

O

O OO

O

P O

O

O

Inhibitors of monooxygenases


Only one biochemical mechanism of resistance to neonicotinoid insecticides was found in fiveyears of research: Microsomal monooxygenases

• 20ml glass vials• 50,000 dpm coated• Transfer of 500 adults• 24h exposure• Homogenisation• Centrifugation• Supernatant TLC

SUD-S ESP-00 GER-01

IMI

I50, nAChR

1.8 nM

23 nMN NH

NCl NNO2

OH

N NH

NCl NNO2

Rauch & Nauen (2003) Arch Insect Biochem Physiol. 54


Cyp6A 14A-Expression

0,0

20,0

40,0

60,0

80,0

100,0

120,0

USA ISR JMB MEX2 Kreta-res

RF = 160

RF = 4

RF >100

Crete

*Data kindly provided by Dr. Juergen Benting (Bayer CropScience, Monheim, Germany)

Biochemistry of neonicotinoid resistance – molecular analysis of B. tabaci P450 genes identified cyp6A14A levels linked to neonicotinoid resistance*


Acetamiprid-selected whiteflies are highly cross-resistant to thiamethoxam, but not vice versa!

N Me

N

N

ClMe

CNAcetamiprid(Nippon Soda)

NMe

NO2

N

SCl NN

H H

Clothianidin * (SumiTake / Bayer AG)

NMe

NO2

N

S NN

O

Cl

Thiamethoxam * (Syngenta)


Strain Origin Date Host plant Biotype

CRE04-01 Crete 2004 Tomato QBR-JM03 Brazil 2003 Tomato BISR-02 Israel 2002 Ornamentals BMEX03-02 Mexico 2003 Tomato BTUC-03 USA 2003 Melon BESP-00 Spain 2000 Pepper QALM-1 Spain 1994 Tomato Q

Insecticide cross-resistance in several strains of Bemisia tabaci

12 (!) different whitefly insecticides (i.e. covering all relevant chemical classes commercially available) were tested in a leaf-dip bioassay (3-4d) against all strains,


Strain SUD-S (insecticide susceptible)

* nymphs


Strain ESP-00 (Q-type)

* nymphs


Correlated are efficacy indices for the compounds displayed. An efficacy index results from mortality figures scoredat different concentrations and subsequently summarized.

y = 0,472x + 203,26R2 = 0,79

100

200

300

400

500

0 100 200 300 400 500

IMI

DTF

y = 1,4592x - 54,2R2 = 0,9289

0

100

200

300

400

500

0 100 200 300 400

TMX

IMI

ALM-1 (1994)

Q-typeB-type

Neonicotinoid cross-resistance in Bemisia tabaci

y = 0,6622x + 186,2R2 = 0,7048

0

100

200

300

400

500

0 100 200 300 400

TMX

DTF

DTF = Dinotefuran

IMI = Imidacloprid

TMX = Thiamethoxam


The alignment was done by minimization of themutual spatial distance of three pharmacophoricpoints, namely

(i) the positively chargedC-atom connected to theN-NO2 and N-CN moiety(ii) the nitro/cyano groupsthemselves(iii) the nitrogens of the aromatic rings

Alignment of DFT/BP/SVP/COSMO optimized geometries of neonicotinoids

Dinotefuran


Pymetrozine is clearly cross- resistant to neonicotinoids in Bemisia tabaci as results from leaf-dip bioassays revealed

IMI = ImidaclopridPYM = Pymetrozine


y = 1,2786x - 144,03R2 = 0,7823

0

100

200

300

400

500

0 100 200 300 400 500

IMI

PYM


Efficacy of spiromesifen and endosulfan against Bemisia tabaci is not correlated w/ neonicotinoid resistance as leaf-dip bioassays revealed

IMI = ImidaclopridSPM = SpiromesifenEDS = Endosulfan

0

100

200

300

400

500

0 100 200 300 400 500

IM I

EDS

y = 0,16x + 333,49R2 = 0,7316

0

100

200

300

400

500

0 100 200 300 400 500

IMI

SPM



Spiromesifen* is highly active against neonicotinoid resistant whiteflies and a new chemical tool in IRM

Active against whitefly nymphs (all stages)

Active against adults at high concentrations

Reduction of adult fecundity (fewer eggs)

Transovarial effects on egg hatch

New IRAC MoA Group 23

Bemisia tabaci

O

OO

O

*


Summary

There is cross-resistance between all neonicotinoid insecticides in field-collected strains of B. tabaci, i.e. selecting with one will impact performance of all others

Pymetrozine seems to be cross-resistant to neonicotinoids

Neonicotinoids are most likely detoxified by oxidative metabolism as elevated P450 levels, synergist studies and in vivo metabolism experiments revealed

Neonicotinoid resistance in B- and Q-biotypes is conferred by different cytochrome P450´s

No target site insensitivity yet found

Spiromesifen is a new chemical option and tool for whitefly resistance management

incidence and mechanisms of resistance in bemisia tabaci ... 2006 q-b… · 874 rf rauch &...

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