Yes, fungi affect more than just dead or decaying organic matter—they may also do harm to the environment by attacking and giving diseases to living plants and animals. In fact, fungi are some of the most harmful pests to living plants and are responsible for billions of dollars in agricultural losses each year. In addition, food products that have been harvested and stored are not immune to fungal decay. Fungi often secrete substances into the foods they attack, making the foods unpalatable or even poisonous.