What to do with pear tree hit by blight?

Special to The Enterprise

This column is written by the Master Gardeners of Yolo County each month. It provides answers to selected questions that recently came into the UCCE Master Gardener — Yolo County Help Desk.

Question: My 3-year-old Asian pear trees seem to have fire blight. All the blossom/small fruit clusters turned black and shriveled up and died. The black is now creeping up the branches.

At this point, should I try to prune back all the branches? Or should I remove the trees?

I have a 20th Century and Shinseki. Thank you for your help!

Answer: We are sorry to hear about your Asian pear trees. What you describe is consistent with fire blight. Fire blight is a disease caused by a bacteria, Erwinia amylovoras. Pome fruits (apple, pear and quince) are susceptible. The bacteria become active once temperatures reach 65 degrees. Rapidly growing shoots are the most susceptible, so symptoms generally begin to show up in the spring. The bacteria can enter through damaged bark or leaves and through blossoms. Once blossoms are infected, the bacteria can be carried from blossom to blossom by pollinators. Because of that, the first sign of fire blight is often shriveled blossoms.

The treatment of fire blight is severe, so you need to be sure of the diagnosis. You may want to take cuttings, in completely sealed plastic bags, to the Master Gardener office (or the MG desk at Farmer’s Markets; see details at yolomg.ucanr.edu), to a local nursery, or to consult with a certified arborist.

Visible symptoms are leaves and branch tips that look “scorched”, hence the name. The ends of young branches will generally have a “crook” which is one of the most characteristic identifiers. But the infection moves under the bark, below the visible symptoms. The only treatment is