Dogs on The Trail of HLB

A team of dogs trained to identify Huanglongbing-infected citrus trees by scent has detected evidence of early HLB infection in commercial groves in Ventura County.

The canine visit was arranged on behalf of the ACP-HLB Task Force by Farm Bureau of Ventura County, which signed a contract with the commercial company that trains and manages the dog teams. Four dogs and two handlers from F1K9, along with the company's operations manager, departed from Florida on July 24 and arrived in Ventura on July 26. Grove scouting began July 29 and ended Aug. 1.

During that time, the team inspected approximately 3,500 trees on 20 ranches in three major citrus production areas: the Las Posas Valley, the Santa Clara River valley, and the Ojai Valley. The dogs alerted on 211 trees, indicating early HLB infection is present in all three areas.

In preparation for the scouting visit, we prioritized potential locations on the basis of four criteria:(1) the presence of "hot spots" where plant and/or ACP samples yielded inconclusive DNA test results during the California Department of Food and Agriculture's periodic HLB surveys; (2) proximity to major transportation arteries; (3) a long history of established Asian citrus psyllid populations; and (4) a low level of participation in ACP suppression efforts by both growers and homeowners.

We also sought volunteers who would allow their ranches to be scouted, agree to pay for the cost (about $4.50 per tree), and agree to remove suspect trees. We agreed to keep the specific locations confidential unless granted permission to share that information by the owner.

The ranches the dogs scouted included one west of Fillmore along Highway 126, one west of Santa Paula without highway frontage, eight at the east end of the Ojai Valley, one outside of Moorpark along Highway 23, one north of Somis without highway frontage, and nine along a 4-mile stretch of Highway 118 west of Somis.

The dogs alerted on a single tree at one of the eight ranches they scouted in the Ojai Valley. Dogs indicated early HLB infection in multiple trees at every other location they scouted.

Although more than 1,600 HLB-infected trees have been confirmed and removed in urban yards in Los Angeles, Orange and Riverside counties, the recent dog alerts here are the first evidence of widespread HLB infection in commercial citrus in California. It is also the first time this early detection technique (EDT) has been deployed for non-experimental purposes, as a tool for commercial growers to make decisions about tree removal to potentially eliminate sources of infection and halt or delay the epidemic's spread. (Up-to-date summaries of the HLB epidemic can be found here: https://www.datoc.us/the-hlb-epidemic).

Because neither the U.S. Department of Agriculture nor the California Department of Food and Agriculture recognize dog alerts as direct proof of the presence of the causal agent of HLB, the canine alerts do not trigger regulatory action. This allows growers to remove suspect trees voluntarily without the complications and cost associated with quarantine requirements that would be triggered by confirmation through official DNA testing.

Despite their non-regulatory status, the dogs' ability to accurately identify early HLB infection in citrus trees has been scientifically demonstrated and validated. The four canines that traveled to Ventura County last month are part of a 19-dog group trained to detect HLB through a multi-year research and development program funded by the U.S. Department of Agriculture and overseen by Dr. Tim Gottwald at the USDA research station in Fort Pierce, Fla. Dr. Gottwald has presented updates on the project at the last four International Research Conferences on HLB, including the most recent one this year in Riverside, as well as at many other scientific gatherings. One of his presentations on the project is available to view online.

The dog's indication of early HLB infection in local commercial groves is a watershed moment in the history of Ventura County's citrus industry. We've long known this day would come, but that doesn't prevent the news from landing as a gut punch. The knowledge we are gaining through strategic deployment of the canine team, however, gives growers here a fighting chance to stem the epidemic's spread while there is still time to do so

And so far, the distribution pattern of dog-alert trees - in general, widely scattered along grove perimeters - suggests we may be catching the epidemic in its very early stages. If this proves to be the case countywide, prompt tree removal and a zero-tolerance policy toward the Asian citrus psyllid - meaning total commitment to the ACP-suppression treatment program - may buy us years of continued viability and profitability even in the face of this threat.

To that point, it is more critical than ever for ACP to be well-controlled: No psyllids means no spread of disease. Growers should continue to treat when asked to for the area-wide treatments. But in addition, Dr. Beth Grafton-Cardwell of UC Riverside now recommends that perimeters be scouted every two weeks, and if psyllid eggs or nymphs are found, that the orchard be treated immediately. These additional treatments, above and beyond the area-wide treatments, must be applied whenever psyllids are found, to keep ACP suppressed below detectable levels.

We are planning to bring the dogs back out for additional scouting as soon as it is feasible. We need to visit other areas that meet the risk-factor prioritization test, so we can establish a baseline picture of how HLB is distributed throughout the county. This will help guide our ACP-suppression and HLB-eradication strategy going forward.

Potential participants are welcome to contact Farm Bureau CEO John Krist for inclusion on the list of properties prioritized for future scouting, so long as they are willing to pay for the cost (currently estimated at about $4.50 per tree), and agree to remove suspect trees. The dogs' time is too valuable and their availability too limited to deploy them where the information they provide won't be acted upon. Ultimately, our intent is to have a team based here permanently, but that will take time and money. We're exploring ways to make it happen.

For a full report on the Ventura County scouting visit, including documents describing the scientific basis of the canine program, go to http://bit.ly/HLB-K9

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