Kaolin as inert material in biopesticide 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.
• Flow through respirometry: LI-7000 CO2/H2O
analyzer combined with IR-actography
– Metabolic rate
– Respiratory rhythms
– Water loss rate
H2O (mlh-1)
lihasaktiivsus (voldid)
5
5
4
4
3
3
2
2
1
1
0
0
30
60
90
Aeg (min)
120
150
180
V H2O µlh-1
V CO2 mlh-1
CO2 (mlh-1)
LD50 = 0.059 mg/bee
Neurotoxic effect
Contact action: alpha-cypermethrin
Dipping in water solution of
Fastac 50EC for 10 sec
0.004%: obtained 0.099 μg/bee
0.002%: obtained 0.087 μg/bee
4
0.004%
DGE => Continuous
VCO2 (ml h-1)
3
2
1
0
0
1
2
3
4
5
6
Time (hours)
Longevity of bumble bees (days)
28
4
DGE => CGE 0.002%
VCO2 (ml h-1)
3
2
1
0
0
1
2
3
Time (hours)
4
5
6
24
20
Median
25%-75%
Non-Outlier Range
Extremes
16
b
b
0.002%
Dist. water
12
8
4
a
0
0.004%
The treatment
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
• Powders have
capacity to prevent
calming process
• Normally water loss
is not changing or
changing a few
• Kaolin and Prestop
Mix caused
significant increase
in WL rate
Metabolic rate (VCO2 ml h-1)
Kaolin
Prestop Mix
BotaniGard
Wheat flour
decrease
increase
Control
-100% -75% -50% -25%
0%
25%
50%
75% 100%
Individuals (%)
Water loss rate (VH2O μl h-1)
Kaolin
Prestop Mix
decrease
increase
BotaniGard
Wheat flour
Control
-100% -75% -50% -25% 0%
25% 50% 75% 100%
Individuals (%)
Respiratory and Cuticular WL
(µl h-1)
• Can be measured during the periods of DGE
• We calculated mean respiratory and cuticular
WL of 3 consecutive cycles of DGE
Respiratory WL
Total WL
Cuticular WL
Respiratory WL = Total WL – Cuticular WL
• No difference in the mean Total WLR during DGE
• No difference in mean Respiratory WL
• Significant differences in cuticular WL
– Kaolin and Prestop Mix
Respiratory Water loss
Cuticular water loss
Mean; Whisker: Mean±SE
Mean; Whisker: Mean±SE
0,8
0,12
Before
After treatment
0,7
V H2O μl h-1
V H2O μl h-1
0,10
0,08
0,06
0,04
Before
After treatment
0,6
0,5
0,4
0,3
0,2
0,02
0,1
0,00
Kaolin
BotaniGard
Control
Prestop Mix
Wheat flour
0,0
Kaolin
BotaniGard
Control
Prestop Mix
Wheat flour
The longevity
• Median longevity
shorter at 18 °C
*** BotaniGard
• Maximum longevity
shorter at 28 °C
• At 18 °C only
BotaniGard differed
significantly
• At 28 °C BotaniGard
and kaolin differed
significantly
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 sublethal effects of pesticides or other stressors