Hello ,
I am working on the potential effect of fungicides on mycelial growth of Alternaria spp ( A.solani , A.tomatophila and A.grandis),
I have noticed for some doses , the inhibitory concentration is different , ie :
- D-1 : Ci%=13,95
- D-2 : Ci%=44,96
- D-3 : Ci%=44,57
- D-4 :Ci%=10,86
- D-5 : Ci%=40,69
These results were obtained by using Bravo ( Commercial noun of the fungicid ) which has a chlorothalonil as active materiel , on A.solani
Is it possible to have this results ? generally , if we apply decrease doses( little ) , the inhibitory concentration should decrease and not increase ?
Humerberto ,
Well i have done all what you have written , and i have noticed that the the Inhibition (%) at (T3--t5) is higher than the I% at (T9---T12), as I said it , we can explain it by toxins...
Beatriz ,
I am using the EC50 ,
Actially i am using the protocol of Segratin and al (1987) , as Humerberto has described before
Thank's for you help
Regards
Narimene
Dear Narimene,
In these experiments, the basic problem is the temperature of the medium and the even distribution of the pesticide in the media. Because of this I put in the media prior to autoclaving suitable magnet. After autoclaving when adding a pesticide, I put the Shott flask with the media on magnetic stirrer to homogenize the culture medium and added pesticide. What kind of inoculum in the test you used, conidia or mycelium pieces?
Regards, Franci
Dear Franci ,
Well i am using the same methode that you have described , except the use of magnetic stirrer , i do it manually ,
For some fungis , I use conidia , for others , i use mycelium pieces and I have noticed similar results for conidia
Regards , Narimene
Dear Narimene,
What is the formulation of the fungicide used? The suspension and emulsion are sometimes difficult to homogeneously distributed throughout the agar medium.
Regards, Franci
Dear Narimene,
There are many of liquid formulations: SL – Soluble Concentrate, SC – Suspension Concentrate, EC – Emulsifiable Concentrate, etc.
Regards, Franci
If you use the commercial fungicide formulation 'Bravo' as your source of chlorothalonil then you are likely to be dealing with a water-based suspension concentrate containing 50% chlorothalonil with inert dispersants. The dispersants are added to the formulation to allow it to be diluted with water while still keeping the chlorothalonil in suspension (as its intended use is for spraying onto plants). You won't be able to dissolve this in any solvent as the dispersants won't dissolve. You would be best to make up your dilution series using sterile distilled water but be aware you will produce a suspension not a solution so you must be very careful to shake it well when making the dilutions and also when adding to your agar. The alternative would be to purchase technical grade or 'pure' chlorothalonil from a chemical company then you could make up your dilution series as a true solution in a suitable solvent. I agree with the others that you should add the fungicide to your media after autoclaving as I'm not sure about the heat stability of chlorothalnil (you could check this).
Dear Louise ,
well I usually put the fungicide after autoclaving the PDA and the fungicide was procured from syngenta
Regards
Narimene
Dear Franci ,
Yes , that's true , in this case , my fungicide is Suspension concentrate
Regards , Narimene
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