it is not so easy, but you can try to use special regimes of light - 12 hours in light, 12 hours in dark

Biruta

I use a 12 h light and 12 h dark in 25 C incubation .

I have attached a paper where I describe induced "hyper-sporulation" in two dothideomycetes. This may help. 

Using near UV light may help, as well as submerging in water. There are some fungi which will only sporulate once stressed, so after the plate has been covers by mycelia pouring 10ml of sterile water and rubbing the mycelia with pippette tip, then placing under near UV light is sometimes works.

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