- Author: John Krist
On Aug. 30, Ventura County's citrus growers, pest-control advisers (PCAs) and pest-control operators (PCOs) embarked on the most ambitious program of Asian citrus psyllid suppression in commercial groves ever undertaken in California. The program involves coordinated pesticide treatments across more than 15,000 acres of citrus in the Santa Clara, Las Posas and Santa Rosa valleys. Hundreds of growers, PCAs, PCOs, grove managers and packinghouse field staff — aided by our county's two grower liaisons and the local ACP-HLB Task Force — are working together to pull it off.
This is the second cycle of area-wide management (AWM) treatments in Ventura County. The first was carried out from January through March in the east end of the Santa Clara River Valley. It involved eight of the county's 49 psyllid management areas PMAs and achieved good compliance, with 87 percent of the total acreage being treated (the rate within individual PMAs ranged from 80 percent to 93 percent).
The current cycle, however, involves 36 PMAs, vastly increasing the program's complexity. It also increases the workload for our PCAs and PCOs, and amplifies the consequences of any disruption in the timetable, which requires that all the citrus in each PMA be treated within a narrow two-week window.
And disruptions are precisely what the program has encountered. The extended periods of extreme heat that have cooked the county over the past two months have idled equipment and crews. At the same time, explosions of other pests — particularly broad mite, flaring under the unusually tropical conditions — have diverted resources to non-ACP treatments to avoid immediate economic harm from damaged fruit.
It remains to be seen whether the crews will be able to get back on track, and finish the fall AWM cycle by the end of November as planned. There is also the chance the applicator crews will encounter further delays, either in the form of extreme heat, Santa Ana winds or early rains associated with the strengthening El Niño condition in the Pacific.
As I have reminded members of Ventura county's citrus community numerous times since we began planning the transition to AWM, our program at this stage is a huge experiment with statewide ramifications.
We can't really draw lessons from areas outside California that are attempting area-wide suppression efforts (Texas and Florida) because their circumstances are so different. We have different weather and topography, for one thing. And Florida in particular did not even try to control ACP until most of the state was also infected with Huanglongbing (HLB) disease, so their program has struggled from the start. Our landscape is also quite different, with none of the giant citrus plantations of Florida and a much more complex pattern of intermingled smaller orchards and urban development than anything seen there or in Texas.
We also have little in common with the few other areas in California that are trying to implement AWM (mainly portions of Imperial and San Diego counties) because we have far more acreage and a much greater number of growers. Eventually, the San Joaquin Valley will find itself implementing AWM, at which point California will finally have an AWM program exceeding ours in scale. The very slow pace of ACP detections there, however, suggests that day is still well in the future.
For now, we have to figure out what works — and what doesn't — on our own. Trying to craft policies and protocols while also attempting to implement them is a bit like trying to build a race car while speeding down the track at 200 mph, but we have no other choice. Think of it as “adaptive management” on steroids.
There have been some very productive discussions among members of the Ventura County ACP-HLB Task Force and our hard-working PCA/PCO community, identifying data needs, logistical constraints and strategy options so we can continuously refine and improve the program. One of our chief challenges is adjusting for our equipment and spray crew limitations while still achieving effective ACP suppression, even when the weather and other pests refuse to cooperate.
One piece of very good news that has emerged at the midpoint of our fall AWM cycle is that the California Department of Food and Agriculture has been conducting timely treatments in urban yards within 400 meters of commercial citrus in each PMA. That did not happen last winter, and the result was swift re-infestation of commercial groves from ACP populations in neighboring landscape plants. At our request, and to CDFA's credit, the agency changed its policy and is no longer waiting to determine the level of grower participation before commencing those treatments.
Countering that, however, are scattered reports of growers refusing to participate — some even going so far as to switch packinghouses in order to avoid the policy instituted by responsible houses to suspend picking and packing fruit from an orchard during the PMA treatment window until the treatment has been conducted.
Evading the treatment requirement is irresponsible and fatally short-sighted. We know for a fact that HLB is less than 50 miles from us, and we also know for a fact that ACP from areas to the south — potentially even infected psyllids — is being transported into Ventura County in loads of bulk citrus. Just recently, a psyllid that tested “inconclusive” for HLB — neither positive nor negative — was collected in Piru. It may be a false alarm, and additional testing of psyllids at the same site will be conducted, but when clusters of such ACP have been found in the past, they have indicated locations where trees soon test positive for the disease.
Holdouts in the Ventura County citrus community must stop thinking of the ACP campaign as a battle against a bug, like so many other battles the industry has fought and won in the past. It is not. Ventura County citrus has never before confronted a tree-killing, insect-vectored disease epidemic, and the tools and strategies of conventional pest management will not stop or control it.
Save the date
To help Ventura County's citrus community better understand the nature of the epidemic — and the bitter lessons from Florida's failure to address it proactively — Farm Bureau and the ACP-HLB Task Force will host a workshop on Dec. 2. As speakers, we've invited three experts whose presentations were among the most compelling at last February's International Research Conference on HLB in Florida:
- Mike Irey, director of research and business development for Southern Gardens Citrus (which farms nearly 15,000 acres of oranges in Florida), who will speak about conditions in his state and provide an industry perspective on what it's like to live with HLB for a decade;
- Dr. David Bartels, an entomologist at the U.S. Department of Agriculture's Mission Laboratory in Texas, who will discuss his analysis of HLB survey data and what it can tell us about possible HLB infection sites throughout Southern California;
- Dr. Neil McRoberts, an epidemiologist and associate professor of plant pathology atUC Davis, whose computer modeling and research into the economic and social factors affecting disease spread can help guide development of an HLB management strategy for California.
The workshop will be from 1 to 4 p.m. on Wednesday, Dec. 2, at the Museum of Ventura County, 100 E. Main St., Ventura. It's free, but RSVPs are required. Please contact us at email@example.com or (805) 289-0155 if you plan to attend.
— John Krist is chief executive officer of the Farm Bureau of Ventura County. Contact him at firstname.lastname@example.org.