As most readers of this blog know, the loss of the pre-plant soil fumigant methyl bromide several years ago presents a serious challenge to business as usual in the California strawberry industry. The search for alternatives, both to the fumigant itself and the practices built up around it over the many decades of its use, has not been an easy one.
Into this fray comes UC Santa Cruz sociologist Julie Guthman with her book Wilted: Pathogens, Chemicals and the Fragile Future of the California Strawberry Industry. She tells the story of how the use of methyl bromide soil fumigation to address soil pathogen problems, from Verticillium earlier, now joined by Fusarium and Macrophomina, has indelibly changed the strawberry industry, from land use patterns, to labor, to publicly supported agricultural science to breeding priorities. In her opinion, the future of our industry has become more tenuous, indeed, in her words is destined to become a landscape of ruin.
To open, the early part of the book really shines and underlines the tremendous amount of research that Dr. Guthman did, as it delves into the history of strawberry culture in California. Beginning from European breeders dabbling with strawberry in the 17th century to the foundation of the California strawberry industry in 1880, then on through the breeding efforts of both the University and private interests (and to be sure, the attendant controversies most of the way), Guthman takes us through a highly interesting tour from the early years of discovery and development to the improvements in productivity, taste and to some extent disease resistance of the modern berry we know today.
As alluded to previously, the book's central argument, built up over several chapters, is the loss of methyl bromide is only the beginning of a fairly dark path forward. She maintains that the strawberry industry in California will cease to be once the chemical fumigants, in particular the chloropicrin which has replaced methyl bromide, become too expensive or are regulated out of existence.
The California strawberry industry, so dependent on fumigants, has been bred for the wrong things and subsequently is not now poised to be particularly resilient to the change foisted upon it by their loss. Breeding has been built around methyl bromide, land use is determined around the ability to fumigate out problems and return to it with little time for rotation and rest, and labor is dependent upon the high yields enabled by fumigation. It all fits together under efficacious fumigation, and will all fall apart without it.
One of the keener aspects of our loss of methyl bromide fumigation has been the emergence of two pathogens, Fusarium wilt and charcoal rot caused by Macrophomina, which has been a question for the scientific community to answer. The author herself wades into this controversy, and floats the idea that epigenetic changes in these two pathogens, that is modification of the expression of the genes rather than the underlying gene code itself, brought on by continual strawberry cultivation and chemical soil fumigation may have resulted in the creation of more virulence and a subsequent emergence as serious pathogens in the strawberry production system.
This view of epigenetic expression resulting in the emergence of these two pathogens, intriguing however it may be, is not well supported by the evidence. A recent paper out of the USDA describes differences in the DNA of the Macrophomina pathogen on strawberry and that of Macrophomina on other hosts. Additionally, the argument that we may have fumigated our way into this problem is significantly undone by strong suggestions that Fusarium was introduced from Japan, where it emerged in the late 1960's - well before fumigation was a widespread practice there.
Dr. Guthman moves on from this survey of what is happening with the loss of fumigation to discuss the alternatives, but is unable to find a suitable fit for replacing what we had with methyl bromide. Anaerobic soil disinfestation (ASD), which is soil flooding with the addition of carbon sources to ultimately create a condition suppressive to pathogens. But since the adoption of ASD by growers in California has been halting, Guthman, along with mentioning an efficacy which often falls short of that of fumigation, underlines that the large amounts of input required, from the amendments themselves to the water to the plastic covering. She also discusses the use of soilless substrates, either in troughs carved out of existing beds or completely soilless systems grown indoors, but again notes the difficulty in this becoming widespread because of cost, technological complexity and necessity of importing inputs.
I believe that Dr. Guthman is not finding the solution she seeks because it cannot be found as a single thing. The answer lies, and I know I am not alone in this view among our scientific community, in a number of practices, not all of them necessarily directed at reducing or resisting soil pathogens, being used together. Developing something this complex takes the input of people from multiple disciplines, and we in the research community, from breeders, to plant pathologists, to pomologists, to growers, both from the public and private sector, have been doing just that for at least the past several years. We don't have the solution yet, but we will get there, I am certain.
A final note is that the book would very much have benefitted from some editing. Errors range from the mundane, such as the incorrect captioning of a picture of recently cut fumigation tarp as being “shredded by the wind”, to the more eye opening such as the unsupported statement of a private sector breeder saying that the UC breeding program under Dr. Shaw and Dr. Larsen did not do disease screens (they did, showed the plots at field days and wrote quite a few papers about them), to the breathtaking such as identifying a REIT (a real estate investment trust, which is a publicly traded company which owns, operates or finances real estate) as a “derivative” such as a futures contract, option, or swap. These sorts of errors tend to undermine one's confidence that the rest of the very well researched story here is true.
Caveats aside, all in all, this new addition to the ever expanding library of commentary on the California strawberry industry is a good one and for those looking for a good detailed description of our industry would be well advised to pick it up and read it.
We humans exhibit complex social behavior. So do honey bees. “Honey bees exhibit complex...
Internationally recognized honey bee geneticist Robert E. Page Jr., recipient of the 2019 UC Davis Distinguished Emeritus Award. (Photo by Kathy Keatley Garvey)
"Honey bees exhibit complex social behavior that rivals our own,” said internationally recognized honey bee geneticist Robert E. Page Jr., recipient of the 2019 UC Davis Distinguished Emeritus Award. (Photo by Kathy Keatley Garvey)
Michael Jordan and Tom Eisner shared at least one thing in common: a rejection that hurt deeply and...
Thomas "Tom" Eisner, the father of chemical ecology, accepts his National Medal of Science award in 1994 from President Bill Clinton for his "seminal contributions in the fields of insect behavior and chemical ecology, and for his international efforts on biodiversity." (Courtesy Photo)
Cornell University chemical ecologists and friends Tom Eisner (1929-2011) playing the piano and Jerry Meinwald (1927-2018) playing the flute. (Cornell University Photo)
Tom Eisner loved chemical ecology--and cars, including this Buick. (Courtesy Photo)
UC Davis chemical ecologist and distinguished professor Walter Leal will deliver the Founders' Memorial Lecture on Thomas Eisner on Nov. 19 at the ESA meeting in St. Louis, Mo. (Photo by Kathy Keatley Garvey)
A Gulf Fritillary butterfly, Agraulis vanillae, sips nectar from the lavender blossom of a...
A Gulf Fritillary nectars the blossom of a passionflower vine, its host plant, while another Gulf Frit flutters in. (Photo by Kathy Keatley Garvey)
A male and a female butterfly find another. These are Gulf Fritillaries, Agraulis vanillae. (Photo by Kathy Keatley Garvey)
A Gulf Frillary caterpillar munching the leaves of a passionflower. Caterpillars will be displayed at the Bohart Museum open house on Nov. 16. (Photo by Kathy Keatley Garvey)
Walking the line. A Gulf Fritillary caterpillar crawls along the stem of a passionflower vine. (Photo by Kathy Keatley Garvey)
Like to learn how to raise Madagascar hissing cockroaches? Bohart scientists will tell you how on Nov. 16 at their open house. (Photo by Kathy Keatley Garvey)
Silkworm moth expert İsmail Şeker, a Turkish medical doctor, will show his newly produced video about the silkworm moth life cycle at 3 p.m., Saturday, Nov. 16. (Photo courtesy of İsmail Şeker)
A male praying mantis, Stagmomantis limbata, as identified by entomologist Lohit Garikipati, UC Davis alumnus. (Photo by Kathy Keatley Garvey)
This is the most recent news about the status of Huanglongbing and Asian Citrus Psyllid in the San Luis Obispo, Santa Barbara and Ventura areas, as well as links to activities in the state. Cressida Silvers is the local Grower Liaison for the Ca Dept of Food and Ag's Citrus Pest and Disease Prevention Program.
The most recent map and totals for all HLB detections in the state are posted at the website maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf. As of November 1, a total of 1,665 trees and 264 ACP have tested positive for the bacterium that causes HLB, on a total of 1,197 sites, all still in LA, Orange, and Riverside Counties. To date, all HLB detections have been on residential properties, the infected trees have been or are being removed, and ACP treatments applied on a recurring basis to remaining citrus in those areas. No HLB has been found in commercial groves via PCR testing.
How Close Is HLB To Your Citrus? There's a New UC App For That!
Visit ucanr.edu/hlbgrowerapp , zoom to or type in your location and it shows your proximity to HLB+ detections, recommends best practices to protect your citrus from HLB based on your current proximity to known detections, and provides a link to the Voluntary Grower Response Plan for more information. As HLB detections via PCR increase and spread, it's important to be aware of possible actions you could take to further protect your citrus should an HLB detection occur in your area.
Regulatory responses required by the state in response to an HLB detection are described in CDFA's Action Plan for ACP and HLB.
UPCOMING CPDPC MEETINGS -- All meeting agendas and eventually the minutes are posted at www.cdfa.ca.gov/citruscommittee/ . All meetings are free and open to the public, and accessible via phone/webinar.
- Operations Subcommittee meets Wednesday, November 6 at 9 a.m. in Visalia.
- Science and Technology Subcommittee meets Wednesday, November 6 at 2:00 p.m. in Visalia.
- The next CPDPC Full Committee meeting will be Tuesday, November 12 at 10 a.m. in Ventura.
CITRUS REMOVAL PROGRAM: Citrus trees that are neglected or abandoned may harbor ACP and HLB, increasing risk to other citrus in the area. Abandoned and neglected trees may be reported to me or the county Ag Commissioner's office. The Citrus Matters ACT NOW program may be able to assist in citrus removal. For more information contact Joel Reyes at email@example.com or (559) 592-3790.
Additional Useful Links:
Summaries of the latest scientific research on combating HLB: ucanr.edu/sites/scienceforcitrushealth/
Science-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
General updates and information on the state ACP/HLB program and regional activities: citrusinsider.org
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)