Title: Citrus industry update
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Title: Citrus industry update
Series Title: Citrus industry update
Physical Description: Serial
Language: English
Creator: Institute of Food and Agricultural Sciences, University of Florida
Publisher: Institute of Food and Agricultural Sciences
Publication Date: August 2007
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Subject: University of Florida.   ( lcsh )
Spatial Coverage: North America -- United States of America -- Florida
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Bibliographic ID: UF00086519
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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UNI VRLSITY f
UI FLORIDA
LI [AS


Working

Citrus Industry Update Iormedou

Published by the Universtiy of Florida, Institute of Food and Agricultural Sciences, with the mission
of keeping the Florida Citrus Industry informed of current research concerning canker and greening.
Welcome to a new effort from UF, IFAS to update progress in research on citrus greening
and canker. This monthly newsletter is targeted to the Florida citrus industry and will provide
ongoing progress in developing base understanding of these diseases, as well as advances
in development of tools for their detection and management in Florida.


GREENING DIAGNOSTICS

S.*Comprehensive comparisons
of existing and new diagnostic
methods are being performed
in several labs to improve on
current detection methods. These efforts
are looking at molecular methods, but
also trying to refine simple, field-ready
techniques that might aid growers in
identifying greening infected trees more
readily or sooner in the infection process.
Methods are being investigated to extract
DNA/RNA from HLB infected citrus trees.
Optimization of several diagnostic methods
is under way.

Improvements continue to be
made in the US Sugar/IFAS Collaborative
diagnostic lab in Clewiston and the
numbers of diagnoses are increasing.
Plans are progressing to develop an
additional lab in Southwest Florida to meet
grower needs.

As a part of our continued efforts
to develop sensitive detection methods
for HLB, we compared the sensitivities
of conventional PCR with Go Taq DNA
polymerase (Promega) and SpeedStar HS
DNA polymerase (Takara) with that of real-
time PCR. We found that the conventional
PCR with SpeedStar HS DNA polymerase
is equally sensitive to real-time PCR. The
conventional PCR with SpeedStar DNA
polymerase can be used as a substitute to
real-time PCR if expensive real-time PCR
equipment and reagents are not available.
(S. Tatineni, CREC, tasa@crec.ifas.ufl.edu)


HLB BACTERIAL INTERACTION
WITH THE PLANT

*Quantitative study of
HLB bacteria populations
inside the phloem is
underway. Specific
fluorescent probes targeting 16r RNA were
designed and tested. Anatomical analysis
of the phloem is underway.

Progress was made in comparing
the gene expression of HLB-infected
citrus trees and non-infected trees from
the grove. Preliminary data are being
developed. This research is also focusing
on HLB-infected citrus trees and non-
infected trees available for investigation
from the greenhouse.

Series of citrus plants are being
infected with HLB under controlled
conditions to understand infection and
symptom development. A range of
responses is being observed in potted
plants, including onset of visible symptoms
within three months following infection.
Other plants are testing positive for
infection after three months but are not yet
showing symptoms. Some information on
varietal response to greening should come
from this work.

continued on page 2


2007 Citrus Research & Education Center, University of
Florida, Institute of Food and Agricultural Sciences, 700
Experiment Station Road, Lake Alfred, FL, 33846, phone: 863-
956-1151.






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continued from page 1
SLocation of citrus greening bacteria
in plant tissues is indicating occurrence of
greening in most tissues investigated. This
research is shedding some light on infection
processes.
CULTURING OF
GREENING BACTERIA

SCulturing methods are
the focus of several projects,
using a variety of techniques
and approaches. We have
not yet cultured the HLB
pathogen. Progress has been made in the
optimization and defining parameters for
growth ofthe babaco bacterium that is being
used as a model system. We still do not have
a consistent source of HLB bacterium in
plants in greenhouses to support extensive
attempts at culturing it. In the interim,
infected materials from the field are being
used to supplement greenhouse sources
of bacteria for culturing efforts. We have
identified a couple of potential systems for
co-culture of the HLB pathogen with other
organisms as alternatives to axenic culture
(Mike Davis mjdavis@ufl.edu)

OTHER BACTERIAL SPECIES
INSIDE THE CITRUS PHLOEM

SSpecies of bacteria other than
Liberibacter are being isolated from citrus
cell culture inoculated with HLB infected
samples. We are currently investigating
those bacteria to determine their identity and
role in citrus tissues. We are also working
to separate internal from external bacteria
from citrus tissues.

THE ROLE OF PSYLLIDS IN
GREENING SPREAD

Psyllid Transmission of HLB pathogen is
an important area of study. It includes:
SWork on acquisition of HLB by adult
psyllids is ongoing
SAcquisition rates ranging from 10-40%
(very preliminary)


Citrus Industry Update
Community Service Bulletin


SNo evidence to date of transovarial
transmission (very preliminary)
SStudy of psyllid transmission rates
ongoing but will take some time before
results can be collected due to latency
period
SResearch on prevention oftransmission
using insecticides is ongoing but again will
take time to determine if transmission has
been prevented due to latency period.
(Michael Rogers MRogers@ufl.edu)

PSYLLID MANAGEMENT

Research
Pesticide efficacy evaluations
A We continue to test new
compounds and timing
of existing pesticides for
effectiveness in controlling
psyllids
SDemonstrated effectiveness of
adlicarb (Temik) for psyllid control in large-
scale trials with evidence that rainfall can
affect the success of Temik applications
SSeveral new products have been
identified as having effects on psyllids and
are being tested further, including products
that could be sprayed during bloom.

Pesticide resistance management
SDetermination of the LC50 values for
currently used products for psyllid control is
ongoing
SWe have successfully determined the
LC50 values for Danitol (fenpropathrin)
SWe have preliminary LC50 data for
imidacloprid
SWith additional funding support, we
expect to have LC50 data for all pesticides
used for psyllid control completed with 12
months
SThis is important for monitoring
pesticide resistance in psyllids in the coming
years) to maintain the effectiveness of the
few products available for psyllid control.

Transgenic Approaches to
Psyllid Management
Drs. Rogers, Dawson and Boucias





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are collaborating to screen more than 100
insect toxins for effects on psyllids that can
be expressed in plants transgenically. Some
preliminary results appear to show some
activity with some toxins.

ASIAN CITRUS
PSYLLID SUPPRESSION

*Timely reduction in Asian
Citrus Psyllid (ACP) populations
is key to reducing spread of
greening in citrus crops. The
highest labeled rate (331bs/acre) of aldicarb
15% (Temik 15G) and reduced rates (16.51bs
and 8.251bs per acre) were evaluated for their
impact on ACP infestations in 2006.

SThe high rate was most effective in
reducing the density of ACP as assessed by
the proportion of citrus flush infested with
eggs and nymphs, numbers of these per
flush and adult number estimates by a beat
method.

SAnother study in 2006 demonstrated
that application on the one side (bed side) of
the trees was as effective as the application
on both sides (bed and swale). Application of
331bs/acre in about 30 days prior to spring
flush in January 2007 was most effective
compared with applications in November or
February.

SReductions in psyllid populations were
detectable for over five months. No impact
of Temik was observed on populations of
ladybeetles known to be responsible for high
levels od predation on ACP. (Phil Stansly,
SWFREC, pstansly@ufl.edu)

IMPACT OF INSECTICIDES
ON ASIAN CITRUS PSYLLID

f *Asian Citrus Psyllid (ACP)
suppression is a key component
of greening management. ACP
can only reproduce on young
flush but survives as adults in
winter by feeding on mature foilage. Broad
spectrum foliar and soil applied insecticides


Citrus Industry Update
Community Service Bulletin


were applied either alone or in concert
with soil application of aldicarb during
the dormant season to suppress adult
populations. The immediate impact on
adult populations and subsequent effect
during the growing season were evaluated
as well as effects on natural enemies. One
application of dormant sprays, significantly
reduces psyllid populations for over 5
months. Reinforcement with aldicarb
generally improved control. Few ladybeetles
were present when sprays were applied
bu reappeared later to feed on aphids and
psyllids in the spring flush. Maintenance of
these presatios may explain the prolonges
suppression of ACP observed. Thus,
dormant sprays appear to be providing
pest suppression for many months with
apparently minimal ecological liability. (Phil
Stansly, pstansly@ufl.edu)

GENETICS AND SEQUENCING
HLB AND CITRUS

*Several independent labs in IFAS are
working to isolate and sequence the DNA
of greening bacteria, and some progress
in isolating clean preparations of DNA
has been made. Partial sequences are
forthcoming, but a compete sequence is
not yet available.

-We are proceeding with efforts to lead
and coordinate the International Citrus
Genome Consortium's project to sequence
a citrus genome by the end of 2008 (one of
the top three highest impact priorities from
the Int. HLB/ACC conference, November
2005) (Fred Gmitter fgg@ufl.edu);

TOWARDS GREENING
RESISTANT CITRUS PLANTS

*Transgenic grapefruit plants have been
produced containing the'Lima'anti-bacterial
construct that has been used in grapes to
create resistance to Pierce's Disease(Jude
Grosser Lab -jwg@ufl.edu).






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STransgenic grapefruit and lime
plants have been produced, containing
a construct that elevates pathogenesis
-related proteins up to 10-fold (Jude
Grosser Lab -jwg@ ufl.edu)

SSuccessful testing of a phloem-
limited gene promoter from Arabidopsis
in Citrus for targeting expression of anti-
bacterial genes in transgenic citrus (Jude
Grosser Lab -jwg@ufl.edu).

SCollection of seedlings of Citrus
latipes (purported genetic resource for
HLB tolerance), to assess tolerance and
inheritance of the trait; (Fred Gmitter -
fgg@ufl.edu)

SSomatic hybridization experiments
have been initiated with the purportedly
tolerantCitruslatipes, andsomaticembryos
recovered have been recovered. Grafted
and ungrafted C. latipes seedlings are
being propagated for greening challenge
to validate this information (Jude Grosser
Lab -jwg@ufl.edu).

SUPPRESSION OF CITRUS
CANKER IN THE GROVE

*Evaluation of copper Materials for
rates, timing and efficacy continues in
Florida and in Brazil through
cooperators

Foliar antibiotic
materials labeled for other
agricultural crop use are being evaluated
for their role in canker management.
(James Graham -jhg@ufl.edu)

MANAGEMENT OF CITRUS
LEAFMINER TO MINIMIZE
CANKER INOCULUM

*IPM approaches are being pursued
to enhance management of Citrus
Leafminer

S Foliar pesticide applications
are being conducted to provide best
management practices for pesticide


Citrus Industry Update
Community Service Bulletin


use for leafminer, psyllid and other arthropod
management

Significant effort is being made to address
inquiries regarding the recent concern over
honeybee decline which is occurring nationwide.
IPM strategies developed for citrus include
avoidance of applications of pesticides when
possible during periods of bee activity (bloom).

WINDBREAKS TO
REDUCE CANKER SPREAD

*Research to identify species
and planting characteristics for
implementing windbreaks in
existing as well as new planting are underway,
with experimental plantings being installed at
several locations.

SDynamics of air flow through natural
windbreaks are being evaluated in existing
plantings of candidate windbreak species.

NEW CITRUS PRODUCTION SYSTEMS
TO RESPOND TO PRESENCE OF
GREENING AND CANKER

SEvaluating new roostocks that are
excellent candidates for use with 'OHS' style new
productions systems that feature high early yields
and shortened grove rotations. Such rootstocks
feature excellent nursery performance, ability to
control tree size, precocious bearing, and wide
soil adaptation (Jude Grosser Lab -jwg@ufl.edu).

SPropagation of several dozen new size-
controlling rootstocks is underwayfor experiments
to examine their suitability for new production
systems (high-density, intensive management,
early economic returns), and their potential to
facilitate vegetative flush control in the Florida
environment; (Fred Gmitter fgg@ufl.edu)

SEvaluating high quality processing sweet
orange clones with reduced juvenile phases,
making them excellent candidates for genetic
engineering in terms of speeding up the process
of commercialization. These clones feature early
fruit production, with even first generation trees
showing high juice quality and minimal thorniness
(Jude Grosser Lab -jwg@ufl.edu).




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