Kaolin as inert material in bio- pesticide formulations supplements - - PowerPoint PPT Presentation

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.

30 60 90 120 150 180

Aeg (min)

1 2 3 4 5

V CO2 mlh-1

1 2 3 4 5

V H2O µlh-1 C O

2

( m l h

• 1

) H

2

O ( m l h

• 1

) l i h a s a k t i i v s u s ( v

• l

d i d )

• Flow through respirometry: LI-7000 CO2/H2O

analyzer combined with IR-actography

– Metabolic rate – Respiratory rhythms – Water loss rate

Dipping in water solution of Fastac 50EC for 10 sec 0.004%: obtained 0.099 μg/bee 0.002%: obtained 0.087 μg/bee

1 2 3 4 5 6 Time (hours) 1 2 3 4

VCO2 (ml h-1)

1 2 3 4 5 6 Time (hours) 1 2 3 4

VCO2 (ml h-1)

0.004% 0.002% DGE => Continuous DGE => CGE

0.004% 0.002%

• Dist. water

The treatment 4 8 12 16 20 24 28 Longevity of bumble bees (days)

Median 25%-75% Non-Outlier Range Extremes a b b

LD50 = 0.059 mg/bee

Neurotoxic 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)

decrease increase

• 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 Prestop

Mix caused significant increase in WL rate

Respiratory and Cuticular WL

• Can be measured during the periods of DGE

(µl h-1)

Cuticular WL Respiratory WL Respiratory WL = Total WL – Cuticular WL

• We calculated mean respiratory and cuticular

WL of 3 consecutive cycles of DGE

Total WL

Cuticular water loss

Mean; Whisker: Mean±SE Kaolin Prestop Mix BotaniGard Wheat flour Control

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

V H2O μl h-1

Before After treatment

• No difference in the mean Total WLR during DGE

Respiratory Water loss

Mean; Whisker: Mean±SE

Kaolin Prestop Mix BotaniGard Wheat flour Control

0,00 0,02 0,04 0,06 0,08 0,10 0,12

V H2O μl h-1

Before After treatment

• No difference in mean Respiratory WL
• Significant differences in cuticular WL

– Kaolin and Prestop Mix

The longevity

• Median longevity

shorter at 18 °C

*** BotaniGard

• At 28 °C BotaniGard

and kaolin differed significantly

• At 18 °C only

BotaniGard differed significantly

• Maximum longevity

shorter 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