Before revision: The most infamous examples are that of Ophiostoma fungi that cause Dutch Elm Disease (DED) and insect Emerald ash borer (Agrilus planipennis) which have specific biologies that lead to severe internal damage of wood and thus tree death, and which make their management extremely difficult or inefficient with classical pesticide application methods.
After revision: The most infamous examples are that of Ophiostoma fungi that cause Dutch Elm Disease (DED) and the insect known as the emerald ash borer (Agrilus planipennis) which have specific biologies that lead to severe internal damage of wood and thus tree death, and which make their management extremely difficult or inefficient with classical pesticide application methods.