UNIVERSITY OF CALIFORNIA
COOPERATIVE EXTENSION
TREE TOPICS
INFORMATION FOR TREE FRUIT AND NUT GROWERS
IN CALIFORNIA’S CENTRAL COAST REGION
JANUARY 21, 2005
VOLUME 30, ISSUE 1________
IN THIS ISSUE:
►FRUIT INSTITUTE
WALNUT INSTITUTE
POMOLOGY DEPARTMENT CHANGES
CHILLING AND REST BREAKING TREATMENTS
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FRUIT INSTITUTE
The Central Coast Counties Fruit Institute will be held on Friday, February 4 from 9 a.m. until noon at
the Veterans Memorial Building in Hollister. This meeting is free and is designed to be of interest to
commercial growers of apricots and cherries. The meeting notice is attached to this newsletter. It is also
available at our web site (cesanbenito.ucdavis.edu) and at fruitsandnuts.ucdavis.edu – the website for the
Fruit & Nut Research and Information Center. Two hours of continuing education credit have been
approved the Department of Pesticide Regulation.
WALNUT INSTITUTE
The Central Coast Counties Walnut Institute will be held on Friday, March 4 from 9 a.m. until noon at
the Veterans Memorial Building in Hollister. This meeting is free and is designed to be of interest to
commercial growers of walnuts. The meeting notice is attached to this newsletter. It is also available at
the two web sites mentioned above. One and one-half hours of continuing education credit have been
approved by the Department of Pesticide Regulation.
POMOLOGY DEPARTMENT CHANGES
The Pomology Department at U.C. Davis is disappearing. The Department of Plant Sciences will now
include pomology, vegetable crops, environmental horticulture and agronomy and range science. The
new department has 85 faculty members, 26 researchers and 119 support staff. One impact is that we will
no longer need to explain that pomology means the scientific study of fruits and nuts.
U.S. DEPARTMENT OF AGRICULTURE, UNIVERSITY OF CALIFORNIA AND SAN BENITO COUNTY COOPERATING
CHILLING AND REST BREAKING TREATMENTS
I have attached an article by Joe Grant (Farm Advisor, San Joaquin County) and Steve Southwick
(former U.C. Pomology Specialist) on rest breaking treatments in cherries. This summarizes most of
what we know about chemicals to induce earlier and more uniform bloom in cherries. The suggested
timing for rest breaking sprays is 550 to 600 hours of chilling at or below 45 deg F for Dormex and 650
to 750 hours at or below 45 deg F for CAN 17 + surfactant.
Some of you have also heard about a new method of calculating chilling called chilling portions. In the
just-published 2004 Cherry Research Reports, the most effective range for application of chemicals
based upon chill portions was listed as 44 to 52 for Dormex and 48 to 56 for CAN 17 + surfactant in a
research report by Steve Southwick, Kitren Weis and Joe Grant . This is still a new technology, so the
safest recommendation is to look at both methods and compare them to your past experience with these
sprays when determining spray timing. The total number of chilling hours as of January 19 is 622 for
Hollister and 516 for Morgan Hill. Both stations are at 50 chilling portions as of January 18.
William (Bill) W. Coates
Farm Advisor, Fruit and Nut Crops
San Benito, Santa Cruz, Santa Clara
and Monterey Counties
(831)637-5346 phone
(831)637-7111 FAX
e-mail: bwwcoates@ucdavis.edu
web: http://cesanbenito.ucdavis.edu/
Univ. of Calif. Cooperative Extension
649 San Benito Street, Suite 115
Hollister, CA 95023
(DO NOT USE ABOVE ADDRESS FOR MAIL)
Mail: P.O. Box 1956
Hollister, CA 95024-1956
For those without Internet access, call or write me and I will provide hard copies of any information mentioned above. Reference to
commercial products or trade names is with the understanding that no discrimination is intended, and no endorsement by Cooperative
Extension is implied.
The University of California prohibits discrimination against or harassment of any person on the basis of race, color, national origin,
religion, sex, gender identity, pregnancy (including childbirth, and medical conditions related to pregnancy or childbirth) physical or
mental disability, medical condition (cancer-related or genetic characteristics), ancestry, marital status, age, sexual orientation,
citizenship, or status as a covered veteran (covered veterans are special disabled veterans, recently separated veterans, Vietnam era
veterans, or any other veterans who served on active duty during a war or in a campaign or expedition for which a campaign badge has
been authorized) in any of its programs or activities.
University policy is intended to be consistent with the provisions of applicable State and Federal laws.
Inquiries regarding the University’s nondiscrimination policies may be directed to the Affirmative Action/Staff Personnel Services
Director, University of California, Agriculture and Natural Resources, 300 Lakeside Drive, 6th Floor, Oakland, CA 94612-3550, (510)
987-0096.
GUIDELINES FOR REST BREAKING TREATMENTS IN SWEET CHERRIES
Joe Grant, UC Farm Advisor, San Joaquin County, CA
Steve Southwick, UC Pomology Specialist, UC Davis, CA
Several treatments are available to cherry growers to promote bud break and advance or shorten bloom, with
lesser but often significant parallel effects on fruit ripening time. The exact modes of action of these treatments
are not well understood, and probably vary slightly among materials. But they all work similarly in concept.
By leaf fall, flower buds for the following season’s crop are fully formed. All parts of the flowers in these buds
are visible, but they continue to develop and mature slowly through winter. Chilling is needed to promote this
and other processes going on in the tree over the winter to prepare the tree for the onset of growth with the
return of warm weather in spring. If this development is slowed by less-than-adequate chilling, rest breaking
(RB) treatments can be used to partially offset this deficiency. Once a RB treatment is applied, trees are put into
a condition in which they will begin to push and grow as soon as the weather warms favorably for growth.
The effectiveness of various available treatments depends mainly on the rate used and treatment timing in
relation to the weather and the condition of the tree at the time of application. Within the suggested ranges of
treatment timings for each product, early applications tend to advance bloom more than later ones, and later
treatments tend to compress bloom more than earlier ones. Since these treatments essentially replace part of
trees’ chilling requirement, they have a more pronounced impact in low than high chilling years. In fact, the
economic benefits of RB treatments should be scrutinized closely in years of adequate chilling, especially when
weighed against the risks of these treatments. In very low chill years, applications should be moved later in the
treatment window for each material, since treatments may stimulate trees before flowers are fully matured. RB
treatments may be ineffective if too little chilling has accumulated prior to the time of application.
There is a risk of phytotoxic effects like killing of buds and/or branches with any of the RB treatments.
Historically, injury has been most common at higher RB treatment rates, later application timings, and with
certain surfactants. Of course, advancing bloom has inherent risks of its own, since the likelihood of frost and
rain is greater early in the spring.
In recent years, researchers, growers, and PCAs have begun accumulating experimental evidence and field
experience on the best way to use RB treatments in cherries, as well as the potential benefits and risks of various
specific treatments. The materials, rates and timings discussed below are those which have given the most
acceptable and consistent results in field trials and grower experience to date. They are provided as suggested
guidelines for growers who wish to begin accumulating experience in using RB treatments as a management
tool. Growers wishing to use RB treatments should proceed carefully, work closely with their pest control
advisor, and treat only small acreages in learning to use these materials.
IMPORTANT: In a September, 2003, enforcement letter to Agricultural Commissioners, the California
Department of Pesticide Regulation (DPR) reversed an earlier opinion that considered dormant season
applications of nitrogen-based fertilizers to influence bud break to be plant growth regulators that must be
registered and regulated as pesticides. US EPA had reviewed the use of these products and concluded that they
do not cause a plant to break dormancy but instead promote a uniform bud break. DPR now acknowledges US
EPA’s position that nitrogen-based fertilizer compounds used post-dormant on trees, shrubs, and vines to ensure
uniform bud break are not pesticides. As a result of this action, California agriculture can use these nitrogenbased fertilizer compounds that are registered as fertilizing materials with the California Department of
Agriculture (CDFA) during the post dormant season to enhance uniform bud break, provided labeling or
advertising does not include express pesticide plant growth regulation claims. CDFA has regulatory authority
over fertilizing materials sold in California. In order to be legally sold as a nitrogen-based fertilizer compound
the product must be registered with CDFA and the labeling and advertising must not include any specific plant
growth regulation claims.
Rest breaking agents
Dormex (hydrogen cyanamide). Research with Dormex has shown that applications at 1-4%
(volume/volume) spray solutions can be effective RB treatments for cherries. Four per cent is the most
common rate used. Treatments are applied roughly 30 days before normal bud break. Experience to date
indicates that Dormex treatments made before trees have received 550-600 hours of chilling at or below
45 ºF may be less effective than those applied later. This is thought to occur because trees are triggered
out of dormancy before flowers have developed fully. Under favorable conditions, Dormex treatments
can advance bloom as much as 10 to 14 days and the first harvest in treated blocks, 7 to 10 days. It has
label restrictions related to use, worker safety, and environmental hazards. Dormex should not be applied
within 7 days of any oil applications because of potential phytotoxicity.
CAN 17 (calcium ammonium nitrate) + surfactant. Tank mixes of 5 to 45% (v/v) CAN 17 and 0.5 to
4% agricultural surfactant have been shown effective as RB treatments for cherries. A number of
available surfactants have been used successfully, including RNA Activator 85, Agri-Dex, Entry, and
crop oils. In general, the best results have been achieved when with CAN 17 based treatments are made
after 650 to 750 hours of chilling at or below 45 ºF have accumulated. There is a risk of phytotoxicity if
treatments are applied less than 3 weeks before bud break. In research trials, CAN 17 + surfactant sprays
have been somewhat less effective in advancing and compacting bloom and fruit ripening than Dormex.
Advancements of 5 to 7 days in bloom and 3 to 5 days in fruit ripening are achievable under favorable
conditions.
Erger + surfactant + fertilizer. Less is known about this treatment than the other RB materials.
Treatment timing and effectiveness are thought to be similar to CAN 17 + surfactant treatments.
Spray oils. Oils are less effective than other available materials for advancing bloom, but have been used
for many years for compacting the bloom period. A number of types of oil are available and effective, and
are generally applied in 4 to 6% spray solutions. Experience to date has shown that effective spray
timings are somewhat later than other RB treatments, around 700-800 hours at or below 45ºF.
______________________________________________________________________________
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WARNING ON THE USE OF CHEMICALS
Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations
given on the container label. Store all chemicals in their original labeled containers in a locked cabinet or
shed, away from foods or feeds, and out of the reach of children, unauthorized persons, pets, and
livestock.
Recommendations are based on the best information currently available, and treatments based on them
should not leave residues exceeding the tolerance established for any particular chemical. Confine
chemicals to the area being treated. THE GROWER IS LEGALLY RESPONSIBLE for residues on the
grower's crops as well as for problems caused by drift from the grower's property to other properties or
crops.
Consult your county agricultural commissioner for correct methods of disposing of leftover spray
materials and empty containers. Never burn pesticide containers.
PHYTOTOXICITY: Certain chemicals may cause plant injury if used at the wrong stage of plant
development or when temperatures are too high. Injury may also result from excessive amounts
or the wrong formulation or from mixing incompatible materials. Inert ingredients, such as
wetters, spreaders, emulsifiers, diluents, and solvents, can cause plant injury. Since formulations
are often changed by manufacturers, it is possible that plant injury may occur, even though no
injury was noted in previous seasons.
CENTRAL COAST COUNTIES
FRUIT INSTITUTE
FOR APRICOT AND CHERRY GROWERS
UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION
FRIDAY, FEBRUARY 4, 2005
9:00 A.M. –12 NOON
VETERANS MEMORIAL BUILDING
649 SAN BENITO STREET, HOLLISTER
9:00
WELCOME AND INTRODUCTIONS
9:05
FERTILIZER & IRRIGATION MANAGEMENT PROGRAM
Mica Nitschke, Irrigation Engineer, San Benito County Water District
9:15
PESTICIDE REGULATION UPDATE
Ron Ross, Senior Agricultural Biologist
San Benito County Agricultural Commissioner’s Office
9:45
INSECT PEST MANAGEMENT FOR APRICOTS AND CHERRIES
Bill Coates, U. C. Cooperative Extension Farm Advisor, Fruit and Nut
Crops, San
Benito, Santa Cruz, Santa Clara and Monterey Counties
10:00
BREAK
10:15
EUTYPA LIMB DIEBACK
CHILLING
ACREAGE AND ECONOMIC TRENDS
Bill Coates, Farm Advisor
11:15
DISEASE MANAGEMENT FOR APRICOTS AND CHERRIES
Dr. Jim Adaskaveg, Associate Professor, Plant Pathology, U.C. Riverside
CONTINUING EDUCATION CREDIT APPROVED FOR 0.5 HOURS OF LAWS AND REGULATIONS AND
1.5 HOURS OF OTHER PEST MANAGEMENT.
ALL DAY PARKING IS AVAILABLE ON EAST STREET BEHIND THE VETERANS BUILDING AND ON
THE BUILDING SIDE OF 7TH STREET. MOST OTHER PARKING HAS A TWO HOUR LIMIT. FOR
FURTHER INFORMATION CALL BILL COATES AT 831-637-5346 OR FAX AT 831-637-7111 OR E-MAIL
AT bwwcoates@ucdavis.edu .
CENTRAL COAST COUNTIES
WALNUT INSTITUTE
UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION
FRIDAY, MARCH 4, 2005
9:00 A.M. –12 NOON
649 SAN BENITO STREET
VETERANS MEMORIAL BUILDING
HOLLISTER, CA
9:00
WELCOME, INTRODUCTIONS
9:05
FERTILIZER & IRRIGATION MANAGEMENT PROGRAM
Mica Nitschke, Irrigation Engineer, San Benito County Water District
9:15
EVALUATION OF WALNUT VARIETIES
VARIETY AND ROOTSTOCK RESISTANCE TO BLACKLINE DISEASE
Bill Coates, Farm Advisor, University of California Cooperative Extension, San Benito,
Santa Cruz, Santa Clara and Monterey Counties
9:45
PESTICIDE REGULATION UPDATE
Ron Ross, Senior Agricultural Biologist
San Benito County Agricultural Commissioner’s Office
10:15 BREAK
10:30 COVER CROPS FOR WALNUT ORCHARDS
Robert Bugg, Information Analyst, Sustainable Research & Education Program,
University of California, Davis
11:00 WALNUT HUSK FLY MANAGEMENT
Bob Van Steenwyk, Extension Entomology Specialist, Department of ESPM – Insect
Biology, University of California, Berkeley
11:30 WALNUT MARKETING BOARD AND CALIFORNIA WALNUT
COMMISSION ACTIVITIES
Dennis Balint, CEO, California Walnut Commission and Executive
Director, Walnut Marketing Board
Continuing education credit has been approved by DPR for 0.5 hours of Laws and Regulations and 1.0
hour of other pest management. All day parking is available on the south and east sides of the Veterans
Building. Most other parking is 2 hour. Enter building from the main (west) entrance facing San Benito
Street. For further information contact Bill Coates at 831-637-5346 or FAX at 831-637-7111 or e-mail at
bwwcoates@ucdavis.edu.
TREE TOPICS
NEWSLETTER
JANUARY 21, 2005
COOPERATIVE EXTENSION
UNIVERSITY OF CALIFORNIA
P. O. BOX 1956
HOLLISTER, CA 95024-1956