If a wide-spectrum fungicide that kills all fungal species were used extensively in a forest, what effects would you expect the treatment to have on the forest vegetation? If a wide-spectrum fungicide that kills all fungal species were used extensively in a forest, what effects would you expect the treatment to have on the forest vegetation? It would harm the few plants that benefit from mutualistic relationships with mycorrhizal fungi. It would greatly reduce the ability of most plants to take up water and minerals from soil. It would benefit plants by killing off fungal pathogens.