Protocol for PDA:

1. Boil 200 g sliced potatoes (peeled will make a whiter medium although unpeeled is perhaps more nutritive) in 1 litre of distilled water for 30 mins. If you don't have distilled water you could use bottled water. Another way is to cook the potatoes at 60 °C for 1 hour.
2. Let it cool and filter through cheesecloth or similar, throw the remaining solids to the compost.
3. In the potato water put 20g of dextrose and 20 g of agar-agar and bring to the boil, stirring vigorously all the time to dissolve all the coagulates of agar-agar. Stir until completely dissolved. You can also pre-dissolve the agar-agar in a little warm water to make the mixing easier.
4. Pour the portions into sterilised recipient such as Petri dish or any small shallow bowl. It doesn't need a cover. These can be sterilised in a pressure cooker 15 mins at 121 °C. If you don't have a pressure cook boil the dish for 15 mins before filling with PDA.


Put the dishes in a place out of direct sunlight where they will not be disturbed. Every day during a period of approx 10 days - or more if you want - take a foto. Various dishes can be put in different places or covered with clingfilm and stored in the fridge awaiting use.