Warcup method is one of the simple, rapid and good techniques for isolating soil fungi. However this method poses significant chance of bacterial infection, a grave disadvantage, so measures for avoiding bacteria are necessary.
In the isolation of soil fungi by the soil dilution plate method, I use Streptomycin Sulfate (powder): to dissolve 1.4 g of the powder in 10 ml of sterile water, than to add 1 mL of the antibiotic solution into 1L of a medium of near 40oC.