Many shrubs and trees suffer from a disease called "fireblight."
Blossoms will suddenly turn brown or black. Leafy twigs wilt from the tip down. Leaves turn brown and shrivel and look as if scorched by fire and then die. Infected branches may hang down and a bend, similar in shape to a shepherd’s crook, may develop. The dead leaves hang on to the twig or branch long after the disease kills them. During the summer, entire shoots or branches wilt and turn dark brown. On branches, and at the base of the blighted twigs, the bark becomes water-soaked in appearance, then turns dark, sunken and finally, dry. Cracks may develop at the edges of the sunken area.
CAUSE- This disease is caused by a bacterium, Erwinia amylovora. Apples, pears (including the popular ornamental pear trees), Pyracantha, Cotoneaster, crabapple, almonds, Loquats, apricots, lilac, plums, Spirea, roses, raspberries, Photinia and quince are among popular fruits and landscape plants that are infected by fireblight.
HOW IT SPREADS- The bacterium spends the winter in sunken lesions (cankers) on the branches and twigs of the host plant. In the spring the bacteria ooze out of the lesion or canker. Bees, flies and many other insects are attracted to the sweet ooze. They carry the infection to the flowers. Blooming plants susceptible to fireblight are then infected. The bacteria spread rapidly in the tissues during warm weather. They attack the blossoms first and are then transported by wind, rain and insects to the leaves, twigs and branches. The cankers or lesions start to encircle the twigs, cutting off the flow of water and nutrients, causing the dieback. In the fall the infection has slowed or nearly stopped.
CONTROLLING FIREBLIGHT-
IN THE SUMMER: Prune out the infected twigs and branches, cutting back into areas 4-12 inches below any visible decay or signs of lesions or cankers. Look for bark that looks water-soaked, or has unhealthy dark, sunken or dry areas. Sterilize the cutting tools between each cut by dipping them in a solution of one part household bleach to 5 parts water. You can also use rubbing alcohol instead of the bleach/water solution. Dipping tools helps prevent spreading the infection to healthy wood. Keep the disinfectant from contacting clothing. Rinse the tools in clear water when finished to prevent corrosion.
NEXT SPRING: Just before the blossoms open, spray the shrub or tree with Lilly-Miller Microcop and Sta-stuck. This is a copper-based fungicide and bactericide. It won't wash off easily. Carefully follow directions on the packages for amounts and methods of mixing. Spray every 5-7 days until the end of the bloom period. This spring spraying is the best chance to control the bacteria causing fireblight and it is very important.
FOLLOWUP- Most shrubs and trees will overcome attacks of fireblight and send out new growth to replace that removed or died. Just be SURE to spray in spring when the shrub or tree starts to bloom. That is the only time you can effectively stop the disease.