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Sunday, June 10, 2012

Watch Out for Deadly Fireblight on European Pear, Asian Pear and Quince

Frequently I see this problem pop up on fruit trees in May or June.
Readers pear tree
Q. 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 from these pictures 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 fireblight but it is not with the new growth.  It seems to have attacked all the places where there would have been fruit. I have inserted pictures for you and hope that these are helpful. It is not receiving any overhead spray.  It is watered with a drip system.   

A. This is fire blight. This is a bacterial disease which 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.

Fireblight in pear
            It can be seen on older growth as well. On new growth if it is present it will show the textbook picture of shepherds hook which I posted on my blog. If new growth was not present then it will simply die back and demonstrate a blackened, scorched, fire appearance.
            This disease is extremely virulent and must remove as soon as possible from the tree and the growing area. 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.

Classic fireblight shepardshook and black
scorched fire symptoms
            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 like Bartlett, all Asian pears and Quince but does not damage Keifer pear. I hope this helps.

1 comment:

  1. Comment from Tom Spellman at Dave Wilson Nursery to me in an email.... He is talking about the disinfectant needed on pruning shears and saws when removing infected limbs and shoots.
    Hey Bob, just a comment on the section where you mentioned Fire Blite. Studies have shown that the only reliable disinfectant for sterilization is a 50/50 mix of household bleach and water. Alcohol and other disinfectants have proven to be almost useless.