May 21, 2011 Fire Blight Launches Spring Offensive Originally published in the Contra Costa Times by Chantal Guillemin, UC Master Gardener Pears, apples, and other common plants are

susceptible to fire blight, a bacterial disease.

SUMMARY Q: What can I do now to lessen fire minal branches. Wind-blown blight damage on my pear trees this raindropscan also spread infection. Fire blight affects many spring? Newly-infected wood takes on a reddish- commonly grown edible brown color and blackens when the and landscape plants, A: Scorched pears clinging to lifeless tissue dies. primarily in the Rose limbs, and blackened, shriveled leaves family. Methods for on crook-shaped terminal branches Managing Fire Blight: managing the disease signal the aftermath of an infection by Fire blight management methods include selecting Erwinia amylovora, the bacterium which include the selection of resistant resistant varieties, causes fire blight. Hosts most cultivars, keeping plants healthy without keeping plants healthy, vulnerable to the ravages of this encouraging vigorous growth, good and good garden pathogen are European and Asian pears, sanitation and the frequent application sanitation. Sprays can apples, quince, crabapple, loquat, of fungicide during flowering. help prevent further serviceberry, juneberry, hawthorn, outbreaks in previously spirea, toyon, mountain ash and Choose tolerant varieties. Many pear affected yards but are pyracantha. Entire trees or shrubs can tree varieties, including Aristocrat, are not cures. become infected and destroyed by fire very susceptible to fire blight. Shinko, blight. Bradford, Capitol and Red Spire are more tolerant. Susceptible apple How the Infection Spreads: varieties are Fuji, Gala, Golden Delicious, The bacterium overwinters in cankers Granny Smith, Gravenstein, Jonathan, which are sunken in the bark of infested Mutsu, Pink Lady, and Yellow Newtown. branches. During our warm and wet Plant early blooming varieties; trees that spring weather, infection can spread bloom late or repeatedly are often from bacteria-filled brownish droplets severely damaged by fire blight. that ooze from these cankers to new, succulent growth. Flowers are the point Cultural practices play an important of entry to the insect-spread infection role in managing fire blight. Avoid which spreads throughout twigs and ter- unrestrained application of nitrogen,

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over-irrigation, especially during bloom, existing ones. Start the first spray and excessive pruning. These practices application on March 1 or after bloom produce plants with vigorous, new begins when the first average daily growth which favors development of the temperature exceeds 60° F. Repeat disease. applications every 4 or 5 days and immediately after rain or hail. Copper Sanitation practices include the can russet fruit so do not apply copper to removal of all infected wood before Anjou or Comice Pears or to Granny “Plant early blooming bloom. Watch for new infections and Smith or Golden Delicious apples after dispose of all prunings from the garden bloom. varieties of pears and or orchard. Continue this practice after the bloom period is over. Don’t use this Summary: apples. Trees that contaminated material in compost. Snip Selection of disease-resistant varieties, off emerging root suckers as they are adequate irrigation, pruning and bloom late or another point of entry for the bacterium. fertilization, careful monitoring for signs In the fall, remove and discard branches of infection, removal of infected wood throughout the season whose foliage turns red, and in winter, and fungicide application can slow the those with dead leaves and fruit. In spread and minimize the damage of fire are often severely spring, excise oozing cankers. blight in gardens and orchards throughout Contra Costa County. damaged by fire A general guideline for removing diseased wood is to cut branches 8” to For More Information: blight.” 12” below cankers. In May or June, You can obtain more information at: when the infection is spreading rapidly, http://ipm.ucanr.edu/PMG/PESTNOTES/pn cuts may need to be made further past 7414.html the point of infection. Disinfect all cutting tools by spraying or by soaking for one or more minutes in a solution of 1 part bleach to 5 parts water. Do this after each cut and after the pruning process. Dry and oil tools after use. Keep in mind that 100% control is impossible.

Spring sprays of pears include copper fungicides or a weak Bordeaux mixture. Fire blight affected branch. Photo: Jack Kelly Clark, These sprays can eliminate the incidence Courtesy UC Statewide IPM Program. ©Regents of of new infections but will not eradicate the University of California.

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