Formidable fire blight tough to tackle

Question: I have a pear tree which is about 10 years old. Up until this year, it has been pretty healthy. This spring, it got a disease. I am hoping you can identify it for me and tell me what I can do to treat it so that it won’t be a problem in the future. I thought at first it might be fire blight, but it is not with the new growth. It seems to have attacked all the places where there would have been fruit. It is not receiving any overhead spray. It is watered with a drip system.

This is fire blight. This is a bacterial disease that is more rare than fungal diseases on plants. One way it is spread is through the flowers, either by blowing wind during rainy weather or by pollinators such as honey bees.

Flowers of apple and pear come from spurs, which are short shoots on older wood.

If the disease enters through the flower, then it will spread through the older growth and into the new growth if it is present. It does not necessarily have to attack new growth. It can be seen on older growth as well.

This disease is extremely virulent and must be removed from the tree and the growing area as soon as possible. Cut out the infected limb to 12 inches below the visible infection. Sterilize pruning instruments with a dilution of bleach and water both before and after the cut has been made.

Put the cut limb into a plastic bag, tie the bag and immediately put it into the trash. Do not try to mulch or compost this infected limb. Oil your pruning tools after you disinfect them with bleach so they don’t rust.

Wash your hands after you have finished pruning. This disease is fairly rare here due to our isolation from orchards and low humidity. It attacks European pears such as Bartlett, all Asian pears and quince but does not damage Kieffer pears. I hope this helps.

Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at extremehort@aol.com. Visit his blog at xtremehorticulture.blogspot.com.