Post on 03-Oct-2021
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