An elm tree stricken by Dutch elm disease with bindweed growing up one side. The bark-boring beetle, a vector of the fungus, Ophiostoma ulmi, is the causative agent of the disease. The sticky conidia of the fungus adhere to the fertilised female beetles & are deposited under the bark where they germinate. Infection spreads rapidly, but is confined to the water conducting vessels of the tree. The symptoms of the disease are yellowing & browning of foliage followed by wilting, defoliatin & finally death.