An elm tree killed by Dutch elm disease. The disease is caused by the fungus Ophiostoma ulmi, which is carried by a bark-boring beetle. The sticky conidia (spores) of the fungus adhere to fertilised female beetles and are deposited under the bark where germination occurs. 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, defoliation & finally death.