Fire blight is the enemy of rosebushes and apple and pear trees. It is caused by a bacteria (erwinia amylovora) which attacks starting generally from the blossoms or flowers and moving up to the twigs and then the branches. Fire blight gets its name from the burnt appearance of affected blossoms and twigs. Flowers turn brown and wilt; twigs shrivel and blacken, the ends often curling. In more advanced cases of bacterial infestation, cankers, discoloured oozing patches, form on branches. The translucent amber or reddish ooze (see image) contains masses of bacteria. Heavy persistent infections can be fatal.