WHY do mushrooms poison each other?

 Some species of fungi, including certain types of mushrooms, produce toxins as a means of defending themselves or competing with other organisms for resources. It is also true that certain toxins produced by fungi, such as phosgene, have been used as chemical weapons in the past. However, it is not accurate to say that mushrooms engage in "chemical wars" or that they use toxins as weapons to capture territory. The production of toxins by fungi is a natural part of their biology and is not part of any intentional behavior on the part of the fungi.