1. D.A. Komm (1), R. Ehsani (2), P. Ravenna (3)
Status of 2017 Huanglongbing (HLB) (Citrus Greening) Multi-Agency Coordination (MAC) Projects on Thermal Treatment of Citrus Trees with Citrus Greening
D.A. Komm (1), R. Ehsani (2), P. Ravenna (3)
(1) USDA APHIS PPQ, S&T, CPHST AQI Raleigh, NC, USA; (2) University of Florida, Lake Alfred, FL, USDA (3) AG Harvesters, Au Gres, Michigan, USA
PROJECT- AG-HARVESTER
INTRODUCTION
FIELD EXPERIMENTS
Title: AG Harvesters Citrus Steam Machine ( CA)
Principle Investigator: Peter Ravenna
Objective 1: Determine the best way to hold a consistent temperature in the canopy of large citrus trees (18’ high x 20’diamter) for continuous thermal therapy
Objective 2: Assemble all parts for field trials.
Objective 3: Field Trials
Research extended for a year
Citrus trees infected with ‘Candidatus Liberibacter asiaticus’ (Las) that have been subjected to steam heat treatments have shown an improvement in citrus yields and vigor (Fan et al., 2013). Thermal treatment equipment is being developed and improved for a range of sizes of citrus trees infected with this pathogen. Two MAC projects are contributing to the development and improvement of this equipment. The status of the two projects is described in this poster.
655 trees
Starting from the beginning of 2015
6 treatments, 4 months, 3 replicates
Aerial images taken in April 2016 & 2017
Harvest yield measured in April 2016 & 2017
Image processing
PROJECT- U of FLORIDA
RESULTS 2016
Title: A Compact, Mobile, and Improved Tree Steaming for Thermal Therapy of Individual Medium-Sized Citrus Trees ( CA)
Principal Investigator: Dr. Reza Ehsani
Objective: Evaluate trees before and after treatment.
Additional field trials at CCLP Manatee Grove
Operational problems such as:
The tracked harvester had insufficient traction to efficiently maneuver in groves.
The canopy was top heavy and susceptible to side wind gusts causing near tip-over conditions.
Testing with the canopy ends open showed excessive thermal loss to the surroundings. All future testing will be conducted with end curtains down.
RESULTS
IMAGE (2016)
NDVI
CENTERS 2016
The effectiveness of thermotherapy can be evaluated by measuring plant physiological characteristics. Changes in yield and Normalized Difference Vegetation Index (NDVI were used as indicators of tree health and were evaluated via analysis of variance (ANOVA) and the Tukey Honestly Significant Difference (HSD) test. The NDVI was calculated from multi-band aerial images obtained with UAV every four months. These images were taken from research plots in which trees were heat treated with different time and temperature treatments in a randomized block design (Images). The results showed that heat treated trees had increases in both yield (Figs. 1-4) and NDVI (Figs. 5-7) values as compared to untreated control trees. The trees that were heat treated for 30 seconds at 60 degree Celsius (highest heat treatment) had the highest increase in yield. However, the average yield was less than other treatments due treatment injury. Thermotherapy does not eradicate ‘Candidatus Liberibacter asiaticus’ (Las), but it does increase yields and could be used to keep trees in production while alternative solutions are developed. Heat treatment in combination with other treatments might be used to control Las.
IMPROVEMENTS FOR 2017
Fig. 1
Fig. 2
Update canopy design and build equipment for better support and safety.
Consider using lighter-weight materials for canopy, frame and hose/tubing.
Add hot water capabilities with additional hot water tank and pumps.
Add another generator to power hot water pumps.
Reduce overhang/cantilevered weight of the canopy to improve safety.
Counter-balance mass added to side track to help level loads.
Consider additional treatments using hot water in addition to steam.
Fig. 3
Fig. 4
Fig. 5
Fig. 6
PROPOSED TESTING FOR 2017
Field trials using the addition of hot water are planned for fall 2017.
Fig. 7
Fig. 1-7
UNTREATED CONTROL
60° C / 30 sec
55° C / 0 sec
55° C / 60 sec
55° C / 90 sec
55° C / 120 sec
CONCLUSIONS
Ag Harvester- ≤ 8’ Trees Prior to HLB Thermal Therapy
Heat treated trees are in better health condition comparing to untreated trees.
Trees treated at 60° C for 30 sec showed better improvement in health although it will take them longer to recover.
Heated trees will be monitored for several years to evaluate the long term effects of heat treatment.
Reference
DEMONSTRATIONS
Fan,G., Xia,Y., Lin, X., Cai, Z., Hu, H., Wang, X., Ruan, C., Lu, L., Sequeira, R., & Liu, B. (2013) Evaluation of thermotherapy against Huanglongbing (citrus greening) under laboratory condition. Proceedings of the 3rd International Research Conference on HLB, Abstract no. 7.23P. Orlando, Florida.
UF Improved System
Ag Harvester
Continuous Steaming