Disease Detection in Citrus

Huanglongbing (HLB) disease has arrived in California and is deadly to citrus trees. Trained working canines can detect an infected tree 2-8 months earlier than currently approved detection methods. Canine detection of Citrus Canker and HLB disease in citrus groves and nurseries in Florida have demonstrated a very high level of accuracy. We would like to be involved in bring trained canines from Florida to California to work with others towards the goal of saving the California Citrus Industry from HLB.

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Canine Project Manager


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Canine Assisted Early Detection of HLB

The underpinning for HLB control is early detection and early response, especially in Texas and California where incidence is low and Arizona where the disease has not been detected. Eventually Florida, which has been devastated by the disease, will likely replant large areas to reestablish the citrus industry. In all of these situations, the optimal control strategy is to inhibit HLB from entering and establishing in commercial plantings. Infected tree removal, to reduce inoculum in the early stage of the epidemic, remains the most effective deterrent to epidemic development. The earlier the detection of Candidatus Liberibacter asiaticus (CLas) infections, especially when asymptomatic or better yet subclinical, the more efficacious infected-tree removal can be. A number of early detection technologies are being explored among which canine detection of CLas infected trees, shows considerable promise. Twenty dogs were trained for early detection via a USDA, APHIS HLB Mac grant. Using 10 dogs, each tested against 1000 trees in replicated randomized “field trials” in a gridded array with varying HLB-incidence, resulted in 99.17% overall detection accuracy. All dogs performed very well with statistically insignificant trends toward false negative or false positives. Each dog has its own personality and interacts slightly differently depending upon the trainer-handler. However, there was no statistical difference in CLas detection by trainer-dog combination. We also explored the use of multiple dogs for confirmation of CLas infections. When two or more dogs alert on the same tree, the tree statistically has a 100% probability of infection. Dogs were also capable of accurately detecting CLas-infected trees exclusively from 5-gm feeder root samples. Using 10 dogs in a time course experiment with ACP inoculated trees, dogs began to detect CLas infections within 2-3 weeks of inoculation, whereas, none of the trees became PCR-positive for CLas until three months post inoculation and the majority of CLas-infected trees required multiple months prior to PCR detection. This confirms that dogs are indeed a very early detection methodology; able to detect CLas in trees with subclinical infection, i.e., before symptom expression and considerably prior to the ability of PCR for detection/confirmation. In field trials of young and mature citrus plantations, canines trot along the rows with an average interrogation time of ~1 tree/sec, most rapid of all detection methodologies. Dogs were also effectively utilized for detection of CLas infected trees in residential areas. Dogs are rewarded for detections by verbal praise and short duration play with handlers. Various deployment strategies will be discussed based on the known spatiotemporal distribution of CLas infected trees.

Abstracts from the 5th International Research Conference on Huanglongbing.  Journal of Citrus Pathology, 4(1).

T GOTTWALD, G Poole, E Taylor, D Hall, J Hartung, D Bartels, D McCollum, M Hil, W Luo, and F Louws. USDA-ARS, Fort Pierce, FL, USA; USDA-ARS, Beltsville, MD, USA; USDA-APHIS, Mission, TX, USA; North Carolina State University, Raleigh, NC, USA.

Use of HLB Detection Canines in Real World Settings

Using canines to detect HLB in citrus has shown extreme promise in the research environment. Tests on different aged infections, different cultivars, roots, and infections from both grafting and psyllids have all shown the dogs abilities to detect and differentiate an HLB infected tree from clean trees at accuracies exceeding 99%. The next logical step is the introduction of the canines to “real world” environments, i.e., commercial citrus plantings and residential or “dooryard” trees to determine if detection accuracy continued. The dogs were introduced to a young grove in Florida first, and trained over the course of several months. However, due to the high incidence of infection in Florida, finding a suitable low disease incidence training area for dogs in a mature grove is almost impossible. The dogs were therefore taken to other states, especially Texas, for training and testing. This also allowed the dogs to work in different environments, different grove management practices, and different citrus species. Another aspect of early canine detection is the use of the dogs in residential environments. Again, using other states for a test bed, the dogs were run through various types of residential areas, including residential neighborhoods, mobile home parks, and even a Buddhist monastery. The dogs showed the adaptability to successfully work in these exceedingly diverse and sometimes environmentally hostile environments. Specificity (in statistical terms the true negative rate) includes the ability of dogs to accurately discriminate between Candidatus Liberibacter asiaticus (CLas) infections and infections by other pathogens or extraneous scent profiles. To accomplish this, a group of the dogs were taken to Beltsville, Maryland and tested against trees held in the international pathogen collection composed of a number of different viral and bacterial citrus pathogen accessions from around the world. The canines consistently differentiated CLas-infected trees and did not alert on trees infected with other pathogens. One unique finding was that dogs trained on CLas were also intrinsically capable of detecting Liberibacter africancus (CLaf) and Liberibacter americanus (CLam) infected trees as well, without additional sensitization or training.

Abstracts from the 5th International Research Conference on Huanglongbing.  Journal of Citrus Pathology, 4(1).

T GOTTWALD, G Poole, E Taylor, D Hall, J Hartung, D Bartels, D McCollum, M Hil, W Luo, and F Louws. USDA-ARS, Fort Pierce, FL, USA; USDA-ARS, Beltsville, MD, USA; USDA-APHIS, Mission, TX, USA; North Carolina State University, Raleigh, NC, USA.

New Approaches to Detection: Canine Surveillance of High Risk Pathogens

The underpinning for control of exotic diseases such as citrus Huanglongbing (HLB) caused by Candidatus Liberibacter asiaticus (CLas) and Plum Pox Virus (PPV) is early detection/response when incidence is low. Unfortunately, these pathogens can remain asymptomatic and subclinical to PCR detection for months yet can act as inoculum sources. Twenty canines were trained for early detection of HLB and two for PPV. Ten canines were each tested against 1000 trees in replicated randomized field trials with varying HLB-incidence, which resulted in 99.16% overall detection accuracy with very few false negatives or positives. Canines also detected infected trees exclusively from 5-gm feeder root samples. In a time-course experiment, canines detected infections within 2–3 weeks of vector transmission, whereas inoculated trees were not PCR-positive for CLas until at least 3–12 mos. post inoculation. In citrus and prunus field trials, canines trot along the rows with an average interrogation time of ~2–10 trees/s; faster than any other detection method. Canines were also effectively utilized for detection of infected trees in residential areas. This confirms that canines are a very early, accurate and sensitive detection methodology. Canines are able to detect the pathogen in trees with subclinical infection, i.e., before symptom expression and considerably prior to the ability of PCR detection.

ICPP 2018 Abstracts of Concurrent Session Presentations: Phytopathology Supplement July 29-August 3, 2018

T. R. GOTTWALD (1), G. Poole (2), G. Mccollum (2), W. Luo PhD (3), F. Louws (4), (1) USDA-ARS, Ft Pierce, FL, USA; (2) USDA, ARS, Fort

Pierce, FL, USA; (3) USDA ARS & NCSU, Ft Pierce, FL, USA; (4) North Carolina State University, Raleigh, NC, USA

Trained Dogs Set to Sniff Out Deadly Citrus Disease

The Fresno Bee: September 17, 2018

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HLB Early Detection Methods Available Now; More Coming Soon

Citrus Industry: October 5, 2018

Link to Article

"Citron"- Alerting on a HLB Infected Tree

"Citron", pictured above, is one of the first dogs trained to detect HLB in 2007. Now retired, she was owned and trained by J & K Canine Academy/Scentworks.

HLB Detection Dogs Coming to California

Citrus Industry: August 22, 2018

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Interview about HLB and Canker Detection Dogs 

Trained by J & K Canine Academy

AgNeTVideo: Citrus Expo 2013-Scent Worx

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"Juice"- The First Canker Detection Canine

Citrus Canker is a disease caused by the bacterium Xanthomonas axonopodis. Infection causes lesions on the leaves, stems, and fruit of citrus trees, including lime, oranges, and grapefruit. Dogs trained by J & K Canine Academy on Canker were a part of a USDA ARS Research Project in Florida. The research results show the canker dogs were over 99% accurate.  Pepe Peruyero, owner of J & K Canine Academy/Scentworxs in Florida is pictured above with "Juice".

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