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Fire Blight


Fire Blight

By Linda Lewis Griffith   UCCE Master Gardener


“Why are the blossoms and leaves on my apple tree turning brown?    Deb R.   Arroyo Grande


Your tree may be infected with fire blight.

Fire blight is a common and frequently destructive bacterial disease that affects pome fruit trees and other related plants.  Pears and quince trees are highly susceptible.  Apples, crabapples and Pyracantha species can also be susceptible to damage. Fire blight infections may destroy limbs and even entire shrubs or trees.

Fire blight is caused by a bacterium, Erwinia amylovora, that overwinters in cankers on twigs, branches or trunks of host trees.  Warm, daytime temperatures between 75 and 85 degrees interspersed with intermittent rain or hail create ideal conditions for bacteria to thrive.  Splashing rain or insects transmit pathogens to nearby blossoms or succulent new shoots.    

Symptoms first appear in spring as trees begin to grow.  A watery, light tan liquid oozes out of infected areas.  The ooze darkens after exposure to air, leaving streaks on branches and trunks. Cankers may be inconspicuous and go unnoticed until later in spring when flowers, shoots and young fruit shrivel and turn black.

Vigorously growing shoots are the most severely affected; conditions such as high soil fertility and abundant water increase the severity of damage. 

Management begins by first selecting varieties of plants that are less prone to damage. For instance, Fuji, Gala, Golden Delicious, Johnathan, Mutsu, Pink Lady and Yellow Newtown are susceptible to fire blight; Empire, Pristine and Williams Pride are considered more resistant. 

Once infections have taken hold, it is necessary to prune out diseased branches.  Cut infected branches at least 8 to 12 inches below the visible injury or canker.  A greater distance below infections may be required on major branches, scaffolds or trunks in May or June when fire blight bacteria are moving rapidly.

To avoid spreading bacteria during the pruning process, dip or spray pruning tools with a 10 percent solution of bleach (one part bleach to nine parts water) before each cut.  Dry and oil tools after use to prevent rust. 


For more information about fire blight, visit these websites:




Posted on Saturday, March 25, 2017 at 1:10 PM
  • Author: Linda Lewis Griffith
  • Editor: Noni Todd

There's Gold on Them Thar Roses

Matched pair: Two multicolored Asian beetles on rose leaves in Vacaville, Calif. (Photo by Kathy Keatley Garvey)

There's gold on them thar roses. No, not the kind of gold found during the California Gold Rush (1848–1855) that...

Posted on Friday, March 24, 2017 at 4:28 PM

Educating the Public About the Bees: Beekeepers Meet the Public at Cal Ag Day

Staffing the CSBA booth and answering questions about bees are (from left) Bernardo Niño of the E. L. Niño Lab, Harry H. Laidlaw Jr. Honey Bee Research Facility, UC Davis Department of Entomology and Nematology; Eric Mussen, California Extension apiculturist emeritus, UC Davis Department of Entomology and Nematology; and Carlen Jupe, CSBA treasurer. (Photo by Kathy Keatley Garvey)

"How are the bees doing this year?" That was the most commonly asked question at the California State Beekeepers'...

Posted on Thursday, March 23, 2017 at 2:55 PM

Congrats, UC Davis Ecologist Louie Yang

Ecologist/associate professor Louie Yang (right) chats with students Geoffey Osgood (far left), animal biology major and Ryan Schemrich, entomology major. (Photo by Kathy Keatley Garvey)

Congratulations, Louie Yang! The ecologist, an associate professor, UC Davis Department of Entomology and Nematology, has...

Posted on Wednesday, March 22, 2017 at 3:44 PM

Citrus! Citrus! Citrus!



All Things Citrus

By Tami Reece UCCE Master Food Preserver


What can I do with all my extra lemons from my garden? Ann B. Nipomo


San Luis Obispo County gardeners are very lucky because with a little frost protection we can grow citrus throughout the winter season well into summer, depending on the varieties. And the best way to extend the citrus season even further is to preserve your harvest. Preservation methods can include pickling, freezing, dehydrating, or canning. On Saturday March 25, 2017, the UCCE Master Food Preservers will have an “All Things Citrus” preserving workshop to show you how. A variety of citrus subjects will be discussed but one of the more unique recipes that will demonstrated is salt preserved lemons. It is a process of salting lemons and preserving in their own juices for up to 30 days. This is a very easy process that results in creating a unique flavorful pickled taste with a wonderful silken texture. They are great in salads, salsa, dips, chicken, lamb, and pasta dishes. You will also be shown how to make lemon curd, a decadent creamy delight that can be used in pies, desserts, pancakes, and even oatmeal but it never seems to last until the next morning at my house!  Finally safe methods to store, preserve, and enjoy oranges will be discussed, as well as marmalades.

The workshop will be held in the auditorium adjacent to the parking lot at 2156 Sierra Way, San Luis Obispo, 10:00 a.m. to 12:00. There will be a $5.00 charge to cover class supplies and you must register at http://ucanr.edu/survey/survey.cfm?surveynumber=19887 as space is limited.

If you have any questions regarding the class or general preserving questions regarding water bath canning, pressure canning, freezing, or dehydrating, you can call our UCCE Master Food Preserver Helpline at (805) 781-1429 and leave a message or email the UCCE Master Food Preservers at slomfp@ucanr.edu. A UCCE Master Food Preserver is available every Wednesday from 1:00 to 3:00 to assist you with your questions.  

To view seasonal preserving recipes, food safety information, articles on food preservation, or other classes available in 2017 from the UCCE Master Food Preservers visit http://cesanluisobispo.ucanr.edu/YouthFamilyCommunities/Master_Food_Preserver_Program/


Posted on Tuesday, March 21, 2017 at 7:18 PM

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