Too bad Bradford Pear are fairly resistant to fire blight. If not, we could probably get rid of them after a few wet springs.
Fire blight is a bacterial disease caused by Erwinia amylovora. You will be tested on this later. It attacks trees in the Rosaceae family like serviceberry, quince, hawthorn, apples and crabapples, photinia, pear, plum and almonds. A lot of the same trees that are susceptible to cedar-apple rust.
What you see in the tree after infection are usually small shoots that look burned and crooked in appearance. In early spring the bacteria enters the stem through natural opening s like flowers or wounds. As the infection or canker enlarges it girdles the stem. The bacterium is spread by rain, wind pruning tools and most of all by bees. As bees visit showy blooms in the spring they spread bacteria from diseased trees to healthy ones and throughout the canopy of all.
This is the disease that has kept us from successfully growing apples in middle Georgia for many years. It is also the reason that I tell folks that want apples or pears in their home orchard; they need to choose resistant varieties. They can’t just choose the varieties that they want. I have seen apple and pear trees killed by this disease in our area.
Once you see the disease there is nothing you can do. You will not bring those stems back to life. If infection is somewhat limited you can prune out the dead limbs. Be sure to make pruning cuts well below (≥4”) the canker and dip pruning tools into a bleach or rubbing alcohol solution to disinfect them between cuts.
If you have susceptible pear or apple varieties and you want to protect them you can spray copper fungicides twice prior to bloom and then spray an agricultural antibiotic like Agri-Mycin every 4 days during bloom. If it rains you will need to reapply. That is why we don’t have apples and pears in every home orchard, and this is why our other pear trees look so bad this year.
A warm winter and wet spring have combined to make this a banner year for plant diseases and fire blight is one of those diseases. So far this year I have seen cedar-apple rust on cedar, fusiform rust on pine, exobasidium leaf gall on camellia, and now fire blight on pears.
This is shaping up to be a great year, if you are a plant pathologist. If you have questions or comments contact your County Agent.
