Fungicides, such as Mancozeb 80% are used in nurseries to prevent the plant root against
pathogenic fungi. These fungicides may have negative impacts on beneficial organisms such as
ectomycorrhizal fungi. Cenococcum geophilum  is an important ectomycorrhizal fungus associated with
some forest trees species.
An in vitro experiment was conducted  in laboratory condition.  Cenococcum  geophilum was
cultured on solid Modified Melin Nokrans’ (MMN) medium containing Mancozeb 80 % at different
concentrations (0, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, and 1000  μM). A completely
randomized design was used with 8 replicates Petri dishes. Mancozeb 80 % decreased the growth of
mycelia of C. geophilum. The radial growth of mycelia was not inhibited by Mancozeb 80 % at 0 to 400
μM concentrations. Fungi-static effect of Mancozeb 80 % was found at 500 to 600 μM concentrations,
meanwhile fungi-toxic effect of Mancozeb 80 % was obtained at concentration more than 700 μM. A
lethal level of Mancozeb 80% to the growth of C. geophilum was not found.