trying out a leaf-dip bioassay to assess susceptibility … · sf1-innvik sogn og fjordane...

Foto: Karin Westrum

Foto: Surendra Dara

Nina Svae Johansen, Marta Bosque Fajardo, Elisa Gauslå, Marit Helgheim (NIBIO)

NORBARAG meeting 6-7 March 2019, Malmö, Sweden

TRYING OUT A LEAF-DIP BIOASSAY TO ASSESS

SUSCEPTIBILITY OF TETRANYCHUS URTICAE TO ACARICIDES

USED IN STRAWBERRIES AND RASPBERRIES IN NORWAY

MITES AND ACARICIDES

2

Foto: Finn Måge Foto: Finn Måge

– Strawberries in open fields and raspberries in tunnels

– Abamectin (Vertimec): MoA 6

– Spirodiclofen (Envidor 240 SC): MoA 23

– Bifenazate (Floramite 240 SC): MoA 20D

– Fenpyroximate (Danitron 5SC): 21A

CONTACT RESIDUAL LEAF DIP BIOASSAY

– 20 «5-leaf»-samples randomly collected throughouteach field, transported to laboratory «over night»

– Minimum 100 individuals isolated and checked for entomopatogenic organisms (1 week)

– Mites reared on strawberry plants until enough femaleadults for testing (22oC, 60% RH, 16 h light)

– 15 adult females transferred to leaf circles dipped in 6-7 consentrations of each acaricide + untreated control offield strains

– Susceptible reference strain for comparison (Ref-2000)

– 3 replicates, 315-360 mites per test

– Incubation at 22oC, 60 % RH, 16 h light

3

Water agar

Transfer of 15 adult T. urticae females to leafdiscs (Ø 2,1 cm)

10 sec.

RF (LC50)Resistance category(preliminary scale)

< 2 0

2-10,9 1

11-25 2

>25 3

4

PROBIT ANALYSIS

– Mortality (dead and affected mites) scored:

• Abamectin: After 48 hours (adults)

• Bifenazate and fenpyroximate: After 72 hours (adults)

• Spirodiclofen: After 7 days (offspring mortality)

– Dose response for ~ 10-90 % mortality

– LC50, LC95 with corresponding 95 % CI

– Reduced susceptiblity assumed if 95 % CI og LC50 do not overlap

Mite strains and history of acaricide use

Mite strain County Crop Collection

date

Acaricides used before

collection

Acaricides used

last 5 years

VA1-Søgne Vest-Agder Strawberry, field 25.04.201624.04.2017 05.07.201709.05.2018

Spirodiclofen-Spirodiclofen, bifenazate-

Spirodiclofen, bifenazate, abamectin

HE1-Ringsaker Hedmark Strawberry, field 10.05.201615.05.2017 31.08.201715.05.2018

--Spirodiclofen, bifenazate-

Spirodiclofen, bifenazate(2 x per year)

VA2-Brøvig Vest-Agder Raspberry, tunnel

07.06.201605.07.2017

-

ThiaclopridFenpyroximate, spirodiclofen, bifenazate-

Spirodiclofen, bifenazate, fenpyroximate

SF1-Innvik Sogn og Fjordane

Raspberry, tunnel

24.05.201622.05.2017 05.06.2018

Fenpyroximate, bifenazateFenpyroximate, bifenazateFenpyroximate, bifenazate

Spirodiclofen, bifenazate, fenpyroximate(3-4 x per year),

SF4-Vangsnes Sogn og Fjordane

Raspberry, tunnel

-27.06.201711.06.2018

-FenpyroximateFenpyroximate

Fenpyroximate

Ref -2000 Laboratory Strawberry - Susceptible referanse strain

5

Vertimec – abamectin (IRAC Moa 6): Adult mortality, 48 h

6

0

0,01

0,02

0,03

0,04

0,05

LC5

0 (m

g ab

ame

ctin

/L)

0,00

0,05

0,10

0,15

0,20

0,25

0,30

Ref 2000 (1) Ref 2000 (2) Ringsaker-2017 Ringsaker-2017(Unexposed 1

år, lab.)

Ringsaker-2018 Søgne-2018 Søgne-2018 Innvik-2018 Vangsnes-2018

LC9

5 (m

g ab

ame

ctin

/L)

Mean of strains: LC50 0,02 ± 0,01 mg AI/L

Mean of strains: LC95 0,09 ± 0,05 mg AI/L

Recommended field dose strawberry (strawberry mite):

• 18 mg abamectin/L (100 ml Vertimec/100 L vann)

Lowest recommended field dose ornamentals (TSSM and other):

• 4,5 mg abamectin/L (25 ml Vertimec/100 L vann)

Envidor 240 SC – spirodiclofen (IRAC Moa 23): Offspring mortality, 7 d

7

0

10

20

30

40

50

60

LC5

0 (m

g sp

iro

dic

lofe

n/L

)

n.c

. mo

rtal

itet

< 2

8 %

1

10

100

1000

10000

LC9

5 (m

g sp

iro

dic

lofe

n/L

)

n.c

. mo

rtal

itet

< 2

8 %

Recommended field dose strawberry:

• 96 mg spirodiclofen/L (40 ml Envidor 240 SC/100 L vann)

Floramite – bifenazate (IRAC Moa 20D), 2016-2017: Adult mortality, 72 h

8

0

50

100

150

200

LC5

0 (m

g b

ifen

azat

/L)

1

10

100

1000

10000

100000

LC9

5 (m

g b

ifen

azat

/L)


• 96-144 mg bifenazat/L (40-60 ml Floramite 240 SC/100 L vann)

Floramite – bifenazate (IRAC Moa 20D), 2018: Adult mortality, 72 h

9

0

2

4

6

8

10

12

LC5

0 (m

g b

ifen

azat

/L)

1

10

100

1000

LC9

5 (m

g b

ifen

azat

/L)


• 96-144 mg bifenazat/L (40-60 ml Floramite 240 SC/100 L vann)

Danitron – fenpyroximat (IRAC Moa 21A): Adult mortality, 72 h

10

0

20

40

60

80

100

120

140

LC5

0(m

g fe

np

yro

xim

ate

/L)

n.c

,max

mo

rtal

ity

< 6

1 %

n.c

,max

mo

rtal

ity

< 2

8 %

n.c

, max

mo

rtal

ity

< 3

4 %

1

10

100

1000

10000

100000

LC9

5(m

g fe

np

yro

xim

ate

/L)

n.c

, max

mo

rtal

ity

< 6

1 %

n.c

, max

mo

rtal

ity

< 2

8 %

n.c

, max

mo

rtal

ity

< 3

4 %

Recommended field dose raspberry:

• 53 mg bifenazat/L (100 ml Danitron 5 SC/100 L vann)

11

BifenazateSpirodiclofen

AbamectinFenpyroximate

2016

RF < 2

RF 2-10,9

RF 11-25

RF > 25

LC50

12



2017

AFTER fieldtreatment

BEFORE fieldtreatment









RF < 2

RF 2-10,9

RF 11-25

RF > 25

LC50

13



2018


RF < 2

RF 2-10,9

RF 11-25

RF > 25

LC50

CONCLUSIONS FROM THE FIVE SITES– No resistance to abamectin

– Indications on initial resistance development to spirodiclofen, bifenazate and fenpyroximate

– Variance in susceptibility profile between sites and years. Explanation?

– Susceptibility to spirodiclofen and bifenazate lower after than before fieldtreatment: important to rotate between MoAs

– Susceptibility to fenpyroximate reduced in all but 2 cases where fenpyroximatehad not been used prior to mite collection

– Susceptiblity seem to be restored to a certain degree when not exposed to bifenazate for some weeks in lab., but not to fenpyroximate (not tested withspirodiclofen)

– High resistance risk Broader resistance survey Resistance monitoringAnti-resistance strategies

14

The «spider mite resistance testing team»

Marta Bosque Fajardo Elisa Gauslaa Marit Helgheim

Thank you for your attention!

trying out a leaf-dip bioassay to assess susceptibility … · sf1-innvik sogn og fjordane...

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