The effect of kaolin and the microbial biopesticides Prestop-Mix and - - PowerPoint PPT Presentation

The effect of kaolin and the microbial biopesticides Prestop-Mix and BotaniGard on respiratory physiology and longevity of bumblebees (Bombus terrestris L.)

Riin Muljar a Marika Mänd a, Reet Karise a, Guy Smagghe b

a Department of Plant Protection, Estonian University of Life Sciences

b Department of Crop Protection, Ghent University

Entomovector technology

• New method
• Bees (foragers) as vectors to distibute plant protection

agents to flowers

• Precise application, smaller amounts of preparations

needed

• Uses powdery biopreparations
• Must be safe
• Plant products (strawberries etc)
• Honey
• Vectoring insect

Effect on respiratory physiology

• Insect respiration
• vulnerable system, easily affected by stressors
• reflects the metabolic rate of the organism
• different respiratory patterns:
• Continuous (Cont.)
• Cyclic (CGE)
• Discontinuous (DGE)

Cont.

Time (min) 3.95 4.95 5.95 6.95 7.95 3000 6000 9000 12000 15000 VCO2 (ml h

• 1)

30 60 90 120 150 0.15 0.30 0.45 0.60 CGE DGE

C O F

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 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
• Muscle contractions

Our experiment

• Are powdery formulations affecting bumble bee physiology?
• Causing respiratory failure?
• Changing cuticule properties?
• Bumble bees (B. terrestris L.): Koppert Biological Systems
• Treatments:
• Prestop Mix - fungus Gliocladium catenulatum,
• Kaolin powder - formulation additive (carrier /diluent)
• BotaniGard - fungus Beauveria bassiana
• Wheat flour
• Blank control

Single topical treatment:

• Immediate effect (N=6 each treatment; 18°C)
• metabolic rate (MR)
• water loss rate (WLR) – respiratory and cuticular WLR
• measured 3 h before and 3 h after treatment
• Long term effect (N=20 each treatment; 18°C and 28°C)
• longevity

Results

Metablic rate:

• No significant differences before

and after treatment

• MR normally decreases during long
• bservation
• Kaolin and Prestop Mix increase MR
• irritation?

Water loss rate:

• Kaolin and Prestop Mix caused

significant increase in WLR

• 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

Respiratory and Cuticular WL

• Can be measured during the periods of DGE
• We calculated the mean respiratory and cuticular WLR of

3 consecutive cycles of DGE

(µl h-1)

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

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

n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.

* *

Longevity

[Temperatuure võrreldes:]

• Median longevity shorter at

18 °C

*** BotaniGard

• Maximum longevity shorter

at 28 °C [Temperatuure eraldi vaadates:]

• At 18 °C only BotaniGard

differed significantly

• At 28 °C BotaniGard and

kaolin differed significantly

Conclusions

• Our results indicate that powdery formulations of microbial

pest control agents may pose some risk to vectoring bees, still the risk is much lower than with synthetic pesticides.

• The standard risk assessment should include physiological

methods, for instance respirometry, and include analyses of the effects of inert materials of microbial pesticides.

Thank you for your attention!