Unwanted mushrooms in polytunnel!

Hi all

Was weeding my polytunnel crops today (toms, peppers, etc) and have noticed a couple of mushrooms poking out of the soil in various places in the poly - I'm wondering whether this is normal, or indicative of a problem, and whether I should remove the mushrooms or leave them be. Are they damaging to crops or beneficial?

What would people suggest?? :cnfs:

Paddy

 

Thanks John - we did indeed apply horse manure!