UF^ UNIVERSITY of
UF FLORIDA -
St. Lucie County Extension 8400 Picos Road, Suite 101, Ft. Pierce, FL 34945-3045 772.462.1660
Treasure Coast Citrus Notes
International Research Conference on Huanglongbing (HLB), "Reaching Beyond
Boundaries" -Orlando, FL, Dec. 1-5, 2008. Citrus Industry leaders and organizations
from around the globe will assemble participants from the international research
community, regulatory agencies and commercial industry to exchange the latest
information on HLB (Citrus Greening). The theme for this exciting conference indicates
a coordinated effort to find commercially feasible solutions for this devastating disease.
For complete information on the conference, go to the conference website:
Citrus Packinghouse Day Thursday, September 11, 2008. Citrus Research and
Education Center, Lake Alfred. Program starts at 9:30 AM. Lunch provided by
DECCO. No pre-registration required.
Indian River Postharvest Workshop Tuesday, September 16, 2008. Indian River
Research and Education Center, Ft. Pierce. Program starts at 9:45 AM. Lunch
provided by JBT FoodTech (formerly FMC FoodTech). No pre-registration required.
For more information on either program, contact Mark Ritenour at 772 468-3922, ext
167 or go to the Citrus Postharvest website, http://postharvest.ifas.ufl.edu/
Flooding in Citrus Groves
The 2008 hurricane season is well underway and Tropical Storm Fay delivered rainfall
amounts from 12 to 24 inches along portions of the Indian River District. Excess water
filled drainage canals and some groves were flooded "trunk-to-trunk" for periods of over
7 days in some instances.
Research at the University of Florida/IFAS Citrus Research and Education Center
showed that there is potential for water damage to citrus trees if water stands over the
crown of the tree for four days or more during frequent extended summer rains. Root
injury may occur when the water table remains a few inches below the soil surface and
roots are not visibly flooded. When that happens, the grower may not be aware of the
potential for root damage. During the cooler months of December through February,
citrus can tolerate flooded conditions for much longer periods than during the hot
Water displaces oxygen and allows anaerobic bacteria (which grow only in the
absence of oxygen) to develop rapidly in flooded soils. Toxic sulfides produced by
anaerobic sulfur-reducing bacteria can build up and kill roots.
With experience, flooding injury can be diagnosed during periods when groundwater
levels are high. Even before there are visible tree symptoms, auguring and digging in
the root zone may give an estimate of future tree condition. Damage can be determined
by digging into the soil and smelling root and soil samples. Sour odors or a rotten-egg
smell (indicating hydrogen sulfide) is a sign that feeder roots are damaged.
Ironically, one of the symptoms of excess water is leaf wilting similar to drought
stress. This occurs because flooding and the lack of oxygen increase root resistance to
water uptake. Inadequate aeration decreases water absorption. Nevertheless,
transpiration, or the loss of water vapor from leaves, continues. Hence, in hot summer
weather, tree water loss can be greater than water uptake trough the roots and wilting
occurs. Because of that, flooding injury occurs sooner in hot weather than in cool
More subtle symptoms include reduced growth and thinner foliage. This can occur
at field locations only a few inches lower in elevation than the surrounding area.
Harvesting operations or other traffic in a grove after recent flooding may further
damage surface roots that have been injured by the flooding.
Hot, dry conditions following flooding will hasten the onset of stress and symptom
expression. The reduced root system resulting from flooding is incapable of supporting
the existing tree canopy. When this occurs, irrigation management becomes critical.
Irrigation must provide moisture to a depleted (shallow) root system, but excessive
water could compound existing problems. Light, frequent irrigations will be required
until the root zone has become re-established. If root damage is severe, frequent
irrigation may even be required throughout the winter months, especially if there are dry
When trying to assess flood damage, Phytophthora problems may also need to be
considered. However, if Phytophthora was not a problem before the flooding, excess
water will not necessarily create one (depending on rootstock tolerance). Therefore,
growers should not make costly soil or foliar fungicidal application for the control of foot
rot and feeder root rot unless soil propagule counts reveal such treatments are
In summary, flooding requires that tree management be intensified to minimize the
effects of stress on water-damaged trees. Flooding will not always damage tree root
systems, but trees should be closely monitored for symptoms. Duration of flooding
conditions, rate of water table drawdown, presence of sulfur or organic matter in the
soil, tree age, rootstock and root condition are all factors to be considered when trying
to evaluate flooding injury and manage tree recovery. Other cultural practices should
be adjusted to minimize stress on water-damaged trees. Fertilization rates and
schedules may need to be adjusted for flood-damaged trees. Light fertilizer applications
are preferred until the root system becomes re-established. Once the immediate
drainage problem has been alleviated, the appropriate course of action is to wait,
observe, and let tree response guide the course of action.
Citrus Greening Mini-Summit
Presented by the Florida Cooperative Extension Service
Citrus Extension Agents
9:45 AM Registration
10:00 AM Psyllid control research and management update
10:25 AM Greening bacteria research update
10:50 AM Break
11:05 AM Horticultural greening management research update
11:30 AM Citrus canker research update
12:00 PM Adjourn
Attendees will receive 2 Continuing Education Units (CEU's) for the Restricted Pesticide and
Certified Crop Advisor Programs.
Speakers/Citrus Extension Agents:
Lake Alfred, FL
863-519-8677 x 108
Ft. Pierce, FL
Meeting dates and locations:
1951 Woodlea Rd
4509 W. George Blvd
2686 SR 29 N
2250 NE Roan St.
1710 Highway 17 South
2199 S Rock Rd
Lake County Extension
Highlands County Extension
SW Florida REC
Turner Exhibition Hall
Polk Co. Ext. Stuart Center
Indian River REC
To register for a specific location of the following locations, please contact:
(Pre-registration is not required but is requested for planning purposes)
Polk County Extension Service
DeSoto County Extension Service
Hendry County Extension Service
Lake County Extension Service
Highlands County Extension Service
St. Lucie County Extension Service
863-519-8677 ext. 111
Pesticide Label Changes
Remedy Ultra 24(c) Special Local need Registration Control of Citrus Resprouts from
Cut Stumps in Citrus Groves. With growers clipping trees for a number of reasons, this
label provides detailed recommendations for sprout control.
Ridomil Gold SL label update The updated label provides and permits specific use
directions for Individual tree treatment for resets/new plantings. The label also permits
growers to tank mix Ridomil Gold SL with other pesticides approved for application to
Florida Citrus. See page 26 of the new label.
Pesticide Applicator Training
Agricultural Tree Crop Pest Control Training and Testing. Preparation for the Private
Applicator or Commercial Applicator test or 3 CEU's for current license holders. The
date is September 18, 2008 (8- 11:30 AM) at the St. Lucie County Ag Center. Cost is
$10.00 and pre-registration is required. Call 462-1660 for registration information.
Pesticide Applicator General Standards (Core) Training and Testing. Preparation for
the General Standards (Core) Test. The date is October 1, 2008 (8:30 10:30 AM).
Cost is $15.00 and pre-registration is required. Call 462-1660 for registration
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St. Lucie County Cooperative Extension
Tim Gaver, Extension Agent II Citrus
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