Synthesis of new formulations of thymol in a view to eradicate varroa destructor J. Aubry1, V. Girod2, F. Ganachaud1 1

Institut Charles Gerhardt - UMR 5253, Equipe "Ingénierie et Architectures Macromoléculaires", Ecole Nationale Supérieure de Chimie de Montpellier, MONTPELLIER, France. 2

Association de Développement de l’Apiculture Professionnelle en Languedoc -Roussillon, LATTES, France

Apimondia 2009, Montpellier, 15-20 September 2009

1

Traditionnal use of thymol against varrosis Number of applications

Total amount of thymol inserted

Mean efficiency (%)

Powdered thymol

2→5

4→60 g

91± 6 %

Apilife Var

2→3

13→ 20 g

86 ± 6%

Thymovar

2→3

13→ 20 g

89 ± 5%

Formulations

Apilife Var (6.7 g thymol/tablet) Vermiculite impregnated with : -76% thymol -16% eucalyptol -4% menthol -4% camphre

2

Thymovar (15g thymol/tablet) Sponge impregnated with thymol

Powder versus solvent formulations a=10 µm a=100 µm

Aspe = 0,05


10

m2/g

Aspe = 0,5 m2/g

Powdered thymol exhibits different crystal size distributions among various samples

Evaporation rate varies sensibly Using liquid amorphous thymol


No specific area differences among samples
Evaporation rate higher for amorphous thymol

Ethanol

cardboard

10 min

Thymol/Ethanol (50/50)

3

Drawbacks of the cardboard method

4

Very good efficiency ( > 90%) but deleterious effects… Overconsumption of the food stock

Laying stopped

Lack of reproducibility Colony desertion

Nymph mortality

What is responsible for these deleterious effects ?
Ethanol left after drying ?


Too high thymol concentration ?

Administration of pure (liquid) amorphous thymol (without ethanol)

Use of pure (liquid) amorphous thymol

5

How to make liquid thymol ? Heat at 50°C a mix of water and thymol (50/50) and put into a separatory funnel.

Wait 24 hours and collect the thymol liquid phase

First experiment: Only one application of a defined mass of amorphous liquid thymol in a small dish next to the flying hole.


A significant amount of amorphous thymol is required to be efficient
No deleterious effects observed : Ethanol must be responsible for bustle

Use of pure (liquid) amorphous thymol

6

Second try: Two applications of 10g of amorphous thymol put on cardboards or on a polyurethane foam Comparison with the traditional thymol/ethanol cardboard method

≈ 80%

Amorphous thymol on cardboards

Amorphous thymol on polyurethane foam

cardboard

Amorphous thymol on cardboards

≈ 65%

Amorphous thymol on polyurethane foam

≈ 60%

cardboard

Increasing specific area to enhance thymol evaporation

7 0.5 μm

Division into tiny thymol droplets in water (diameter=0.5 µm)

Emulsion of thymol

S = 30 cm²/g

S = 2.106 cm²/g

Evaporation rate

Liquid amorphous thymol

Decreasing thymol droplet diameter

Increasing Thymol evaporation rate Droplet diameter

Synthesis of aqueous thymol emulsion by solvent shifting eau (W) Water (+stabilizer + tensioactif) ()

thymol huile + solvant + hydrophilic hydrophile solvent (S) (ethanol or acetone) (+ tensioactif) ( )

8

Solvent evaporation

tiny droplets of thymol in water + solvent

tiny droplets of thymol in water

Aqueous solution

Organic solution

8

Preliminary experiments with thymol emulsions

9

Formulation

Stabilizer

Droplet diameter (μm)

administration

F1

Brij 56

0.6

0.8 g sprayed

F2

Brij 56

0.8

0.8 g sprayed

ENS1

Brij 56

0.26

1.2 g impregnated on sponge

ENS2*

Brij 56

0.3

1.2 g impregnated on sponge

* Coprecipitation with a polymer

Other treatments

 Turbovar: thymol vapors  Bb carnauba: mushroom spores  Cardboards: EtOH/thymol cardboards

Second experiments with thymol emulsions

≈ 35%

≈ 45%

10

Efficiencies quite low but 0.8 g and 1.2 g thymol inserted instead of 30 g inserted commonly !

Conclusions

11


Thymol/Ethanol cardboards method efficient but too many deleterious effects and poor reproducibility
Use of amorphous thymol gives better efficiency without deleterious effects
Aqueous thymol emulsions are suitable for spraying inside hives but thymol concentration needs to be optimized (too large volume sprayed)
Evaporation rate of thymol unknown to compare our different formulations

Next steps

12


Synthesis of new emulsions containing higher thymol concentration


Flux chamber: determination of thymol concentration in air Gas-Chromatography [Thymol] air + thymol

air

sample

air

Real knowledge of the evaporation rate of our formulations

Aknowledgements 13

For fundings

For fruitful collaboration

For accepted presentation