Kaolin as inert material in bio-pesticide formulations supplements

the hazard to useful insects

Reet Karise

Riin Muljar

Marika Mänd

Pesticide studies

• Field exp

• Semi-field exp• Mortality tests

• Behavioural exp• Learning

• Choice

• PER

• ...

• Physiological exp– Dissection

– In-vivo?

Respiration

• Reflects the metabolic rate of the organism

• Easily vulnerable system

MR and respiratory patterns

Continuous (Cont.)

Cyclic (CGE)

Discontinuous (DGE)Cont.

0 30 60 90 120 150 180

Aeg (min)

1

2

3

4

5

V C

O2 m

lh-1

0

1

2

3

4

5

V H

2O

µlh

-1

CO2 (mlh-1

) H2O (mlh-1

) lihasaktiivsus (voldid)

• Flow through respirometry: LI-7000 CO2/H2O analyzer combined with IR-actography

– Metabolic rate

– Respiratory rhythms

– Water loss rate

Dipping in water solution ofFastac 50EC for 10 sec

0.004%: obtained 0.099 μg/bee0.002%: obtained 0.087 μg/bee

0 1 2 3 4 5 6

Time (hours)

0

1

2

3

4

VC

O2

(ml h

-1)

0 1 2 3 4 5 6

Time (hours)

0

1

2

3

4

VC

O2

(ml h

-1)

0.004%

0.002%

DGE => Continuous

DGE => CGE

0.004% 0.002% Dist. water

The treatment

0

4

8

12

16

20

24

28

Lo

ng

evit

y o

f b

um

ble

bees (

days) Median

25%-75%

Non-Outlier Range

Extremes

a

b b

LD50 = 0.059 mg/beeNeurotoxic effect

Contact action: alpha-cypermethrin

Entomovector technology

• New method

• Uses powdery biopreparations

• Decreases the amounts of preparations needed

• Must be safe

– Plant products

– Vectoring insect

– Insect products (honey)

Kaolin• Kaolin powder

– Used against stored product pests

– Causing respiratory failure?

– Changing cuticule properties?

• Kaolin particle film

– Physical barrier/deterrent

– visually or tactilely unrecognizable as a host

• Kaolin is frequently used as inert materials in bio-preparations

Our experiment

Are kaolin and powdery formulations affecting bumble bee physiology?

• Bumble bees: Koppert Biological Systems

• Treatments: – Kaolin– Prestop Mix (Gliocladium catenulatum)– BotaniGard (Beauveria bassiana)– Wheat flour – Blank treatment for control

Single treatment, immediate effect (N = 6; 18 °C)

– Immediate effect on metabolic rate and water loss rate (measured 3 h before and 3 h after the treatment)

– Effect on cuticular and respiratory WL

Single treatment, long term effect

– Effect on mortality (N = 20; 18 °C and 28 °C)

Results• MR normally

decreases during long observation

-100% -75% -50% -25% 0% 25% 50% 75% 100%

Kaolin

Prestop Mix

BotaniGard

Wheat flour

Control

Individuals (%)

Metabolic rate (VCO2 ml h-1)

decreaseincrease

-100% -75% -50% -25% 0% 25% 50% 75% 100%

Kaolin

Prestop Mix

BotaniGard

Wheat flour

Control

Individuals (%)

Water loss rate (VH2O μl h-1)

decrease

increase

• Normally water loss is not changing or changing a few

• Powders have capacity to prevent calming process

• Kaolin and PrestopMix caused significant increase in WL rate

Respiratory and Cuticular WL

• Can be measured during the periods of DGE

(µlh

-1)

Cuticular WL

Respiratory WL

Respiratory WL = Total WL – Cuticular WL

• We calculated mean respiratory and cuticularWL of 3 consecutive cycles of DGE

Total WL

Cuticular water lossMean; Whisker: Mean±SE

KaolinPrestop Mix

BotaniGardWheat flour

Control0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

V H

2O

μl

h-1

Before After treatment

• No difference in the mean Total WLR during DGE

Respiratory Water lossMean; Whisker: Mean±SE

Kaolin

Prestop Mix

BotaniGard

Wheat flour

Control0,00

0,02

0,04

0,06

0,08

0,10

0,12

V H

2O

μl

h-1

Before After treatment

• No difference in mean Respiratory WL

• Significant differences in cuticular WL

– Kaolin and Prestop Mix

The longevity

• Median longevityshorter at 18 °C

*** BotaniGard

• At 28 °C BotaniGardand kaolin differedsignificantly

• At 18 °C onlyBotaniGard differedsignificantly

• Maximum longevityshorter at 28 °C

Conclusions

• Kaolin increases permeability of insect cuticle to water vapour

• This may affect the survival of individuals

• The testing inert materials is not obligatory

• Yet these might pose risks to pollinators or vectoring insects

• Physiological methods, for instance respirometry, can be one way to discover sub-lethal effects of pesticides or other stressors