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Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
California Department of Food and Agriculture (CDFA which also oversees much of CCC's Department of Agriculture) released documents March 21st announcing that Asian Citrus Psyllid (ACP) had been found March 6 in both El Sobrante (centered but includes portions of Richmond and El Cerrito) (https://www.cdfa.ca.gov/plant/pdep/treatment/notices/2017/ACP-NOT-ElSobrante-ContraCosta-March-2017.pdf) and Pleasant Hill (plus portions of surrounding cities) https://www.cdfa.ca.gov/plant/pdep/treatment/notices/2017/ACP-NOT-PleasantHill-ContraCosta-March-2017.pdf). CDFA also announced that with cooperation of the CCC Agriculture Commissioner, they will soon commence with treatment to hopefully eradicate those found and prevent further spread.
Brownish adult, yellow nymphs, and white wax of the Asian citrus psyllid, Diaphorina citri
Click the map images for full page size maps
With ACP found in CCC and if you are growing citrus in your garden, you are strongly encouraged to check your citrus for ACP presence . Helpful UC IPM web guidance can be found at http://ipm.ucanr.edu/PMG/PESTNOTES/pn74155.html#PSYLLIDVIDEO (with video on how to detect ACP) as well as the CDFA web site (https://www.cdfa.ca.gov/plant/acp/).
Help Desk of the UC Master Gardener Program of Contra Costa County (SIM)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/)./span>
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:
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