Which of the following are two exotic fungi that remain uncontrollable today?

The correct answer highlights two significant invasive fungi that have had a profound impact on tree species in North America. Dutch Elm Disease, caused by a fungal pathogen, has devastated elm populations, leading to the decline of these once-common trees in urban and rural settings. The disease spreads through beetles that carry the fungus, and despite various attempts at control and management, it continues to be a major threat to elm trees.

Chestnut Blight, caused by the fungus Cryphonectaria parasitica, virtually eliminated the American chestnut tree. This tree was a dominant species in eastern forests before the introduction of the blight in the early 1900s. Efforts to breed resistant tree strains have shown promise, but the original chestnuts remain largely absent due to the ongoing presence of the blight.

Overall, both of these fungal diseases illustrate the challenges that arise when invasive species are introduced into an ecosystem, highlighting the importance of awareness and management of exotic pests and pathogens in forestry practices.