thermotherapy: putting the latest results to work for you · 2016. 10. 10. · thermotherapy:...
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Thermotherapy: Putting the Latest Results to Work for You
Dr. Reza Ehsani
Professor
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Choosing a Time-Temperature Combination
1. Determine what heating method is most adaptable to the plant material.2. Select a temperature-time combination through experimentation.
(Grondeau et al., 1994)
(Image reproduced from
Baker, 1962)10/10/2016 2
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Does thermotherapy work?
Schwarz, R. E. and Green, G. C. 1972, October. Heat requirements for symptom suppression and inactivation of the greening pathogen. In Proceedings of the Fifth Conference of the International Organization of Citrus Virologists (pp. 44-51).
In South Africa, 1972
112°F
115°F
118°F
122°F
126°F
130°F
133°F
136°F
Test of Phloem Temperature using Steam
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Temperature of Phloem (in red) vs. Time
5
Distribution of CLas within a potted greenhouse-grown citrus plant
Li, W., Levy, L., and Hartung, J. S. (2009) Quantitative distribution of 'Candidatus Liberibacter asiaticus' in citrus plants with citrus huanglongbing. Phytopathology, 99(2), 139-144.
Li et al. (2009) visualized the quantitative distribution of the Clasbacteria in potted greenhouse-grown citrus trees which had been inoculated with the CLasbacteria 5 years earlier.
• Engineering aspectsThe engineering aspects of thermotherapy treatment deal with building systems and machinery that can effectively and economically heat treat a large number of trees in a timely and efficient manner.
• Science of thermotherapyThe science of thermotherapy is trying to answers questions about how thermotherapy works, such as: • Does the heat really kill the bacteria, and if so what percent of them
are killed at a given dosage? • Does heat trigger a response in the tree that alters the disease
expression of HLB? • What factors affect the repeatability and efficiency of
thermotherapy treatment? • What is the best time of the year to apply thermotherapy? • What is the best duration and temperature combination to kill the
bacteria while minimizing tree damage?
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Does Thermotherapy Work?
Step 1: System is positioned next to tree Step 2: Enclosure is placed over tree
Step 3: Steam is applied to treeStep 4: Enclosure is raised before
moving to next tree
Full
Process:
2-4
minutes
Rate of
Treatment:
15-25
trees
per hour
Progress on Engineering Objective• Graphic User Interface (GUI) developed for the current
thermotherapy system
• Model of heat distribution
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THERMOCOUPLE LOCATIONS
Uniformity of the Generated Steam Distribution
OPERATOR CONTROLS
Commercial Thermotherapy Systems
Premier Energy Services, Inc.
Ag Harvesters
ScoringAg, Inc.
Larry Davis
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Lykes Bros Inc.
Project Heat
a| Provide an enhanced scalable steam-generated thermotherapy treatment as an immediate short-term solution for sustaining productivity of HLB-affected citrus trees.
GOALS b| Study and develop procedures for optimized heat treatment techniques that provide the maximum reduction of HLB-causing bacteria and prolong the effectiveness of treatment while reducing any possible adverse effects on crop yield and fruit quality.
Collaborative effort between researchers in multiple
fields: engineering, plant pathology, plant physiology, cell
biology, nematology, and food science
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Treatments:
UTC T0
140°F/30s T1
131°F/0s T2
131°F/60s T3
131°F/90s T4
131°F/120s T5
Field Trials
Treatments in October 2015
Treatments in July, 2015
Treatments in October, 2015
Treatments in February, 2016
Treatments in May, 2016
Evaluating Heat Treatment Effectiveness
1. Polymer Chain Reaction (PCR) Analysis 2. PMA-PCR Analysis 3. Fruit Quality Measurements
• Fruit Yield• Fruit Drop• Juice Quality
4. Tree Health Measurements• Leaf Water Potential – how HLB affects the water transport system of the tree• Stomatal Conductance – directly related to transpiration which is an indication of
overall tree health• Leaf Anatomy – petiole cross-sections are evaluated for the damage done to HLB-
affected phloem cells• Chlorophyll Fluorescence – directly related to overall tree health• Green Index – vegetation index directly related to overall tree health
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Plant Moisture Stress (PMS)
Pressure bomb model 615
Sap flow
Thermal Dissipation Probe (TDP) transpiration sensor by Dynamax.
Stomatal Conductance
(SC-1 leaf prometer by Decagon devices)
Leaf area index (LAI)
ACCUPAR LP-80
http://dynamax.com/ http://www.decagon.com/
Data Collection
Water Uptake Measurement
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MT
NT
OT
UTC
Treated in Oct. Severe Treatment (60°C/30s)
Treated in Feb. Severe Treatment (60°C/30s)
Untreated Control
Treated in Oct. Mild Treatment (55°C/0s)
Water Uptake Measurement
Average daily water uptake rate after heat treatment
0
5
10
15
20
0 50 100 150 200Wat
er
Up
take
Rat
e
Time ( in days)
UTC
MT
OT
NT
Results
Multi-Band Aerial Image
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Results
Percent change of NDVI value for different heat treatments after two months
Effect of Heat Treatment on Citrus Fruit Yield After the First Year of Thermotherapy
-50
0
50
100
150
200
250
300
350
UTC 140/30 131/0 131/60 131/90 131/120
Yie
ld, (
lb/y
ear)
Temperature (F) / Time (s)
July October February
The Effect of Summer Thermotherapy Treatment on Clas Titer One Month after Treatment Compared to Pretreatment Titers
• Heat treatment in the spring and summer is more effective based on general canopy health.
• The bacteria from the roots can move to shoots faster than what was expected, and this may require multiple heat treatments.
• An absence of CLas from the treated leaf material was not observed from the summer treatment.
• A better method of detecting live vs. dead bacteria is needed.
• Water uptake rate initially decreases after heat treatment but will recover about 2 months after heat treatment.
Summary
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Acknowledgements
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Dr. Dewdney Dr. JohnsonDr. ToudeshkiMs. PertiwiMs. SouriMs. BuchanonMr. TrotochaudMr. Sweeb
