Thursday, October 31, 2019

Anything Scary About California's Produce Options This Halloween?

California Food Safety Check

Each year the California Department of Pesticide Regulation (CalDPR) collects produce samples from multiple steps between the farmers and consumers. They recently released their results for 2018.  They tested a total of 3,666 samples of 140 different crops grown in California, other US states and items that were imported from 25 different countries.  For each sample they analyzed for 400 different pesticides or their known breakdown products.  This is also part of an enforcement program so it is great that they are still so transparent with their findings.

As with previous surveys, the results document the fact that the growers who produce our food are following the EPA label requirements that are designed to insure that by the time it gets to consumers is quite safe.  That safety standard is based on national standards set by the EPA.  For 78% of the crops there we either no detectable residues or residues below the legal limits. Few of the remaining examples were at all problematic

Particularly for the US grown samples, excessive concentrations were very rare.  There were some residues of chemicals found which are not technically supposed to be used on that crop, and as in the past most of these “no established tolerance” cases were on the imported items.  

The residue issues varied quite a bit by source. Those from different parts of the US were similar, but those from China, Mexico and Central America had more cases of "no tolerance." Perhaps the best profile was for crops imported from South America.

301 of the items were being sold as “Organic.”  The rule for organic set by the USDA is that no detected residues should exceed 5% of the EPA tolerance .  In 2018 only 55.4% of detections from organic sample met that standard so they should not have been able to be sold as "USDA Organic Certified."  Imported organic residues over 5% of the tolerance made up 66.7%  of detections which is very similar to that same measure for domestic conventional produce.  55.4% of the detections on imported conventional crops would not have disqualified them if someone was trying to sell them as organic.  Below is the list of specific pesticide residues that were found on organic samples.   


Those who think they are buying something safer by spending more for organic might want to rethink that logic. Only the 16 spinosad detections represent something allowed for use on organic, and organic still has the legacy of residual DDT metabolites like DDE.

While CalDPR made it very clear that this report was good news, they called out seven commodities for which they though the residues could be a legitimate health concern. These are Dragon Fruit (Vietnam), Chayote (Mexico), Lychee (China), Cactus Pear (Mexico), Star Apple (Vietnam)m and Tomatillo (Mexico).  They also added Star Apple from Vietnam  and Guaje from Mexico because of products found there for which there is no set tolerance.

Once again this is evidence that our food supply is safe and also incredibly diverse. This testing program is different from the USDA’s Pesticide Data Program (PDP) in that it includes a number of more exotic items. However it also includes many more mainstream fruits and vegetables and among those there were no above-tolerance detections. But in both cases the take-away is that we should enjoy our fruit and vegetable options and consume them as part of a healthy lifestyle.


Monday, October 7, 2019

Don’t buy organic food if you want to seriously address climate change

As we approach the 2020s, many consumers have accepted the marketing/activist narrative that organic farming would be the best option for food safety and to mitigate the most damaging effects of climate change. The inconvenient truth is that organic farming is a terrible option from a climate change perspective. Its dependence on manures and compost involves huge, but rarely recognized, greenhouse gas emissions in the form of very potent methane and nitrous oxide.
But perhaps its biggest climate change issue is that organic farms are mostly less productive per unit area than “conventionally” farmed land. With rising food demand driven mostly by rising standards of living in the developing world, there is a need to boost farm production, and that means the very undesirable conversion of forests or grasslands to agriculture in places like Brazil. That leads to major carbon dioxide release from what had been sequestered carbon in the soils, and also the loss of biodiversity and other environmental services provided by those natural lands.
Background on “organic” farming
The organic farming movement started in the late 1800s and early 1900s in response to issues that had arisen in plough-based agriculture, which had converted most of the prairie land in the American Midwest to farmland through the process of sod-busting.
Spurred by the Homestead Act, Americans moved to the Midwest to claim their 640 acres of government land give-away. Most used the new polished steel plow made by the John Deere company to turn what was once a diverse grassland ecosystem into what became one of the most productive agricultural regions in the world. However, the way that these farmers needed to control weeds and make the land suitable for planting was to mechanically disturb the soil, and that lead to the death of many soil organisms and the breakdown of the organic matter that they had made using the energy supplied by the plants that grew there.
Over time, as the soil was degraded by this tillage, it became less fertile, less able to capture and store rainfall and less productive. The common solution was often to move on to “virgin” land and do the same thing to the biome there.
The true innovation of the early organic movement was the realization that for a soil to remain productive over time, the organic matter content of the soil had to be replenished after each crop harvest. The movement’s solution was to import large quantities of organic matter from other sites in the form of the manure or composted manure from the animals fed on those other agricultural acres. This worked, but it was never, nor is it now, a viable solution for US or global agriculture.
Even so, starting with the Rhodale Institute’s publication of “Organic Gardening” magazine in the 1960s and the eventual establishment of a commercial organic industry in the 1970s, the mostly non-farmer consumers in US society were told the story that organic farming was the best way to both feed us and protect the environment.
In 1990, the USDA (US Department of Agriculture) was charged by Congress with establishing a national organic standard to supersede the fragmented certification systems that had evolved to that time. It was a major struggle because the very science-oriented USDA was at odds with the early organic marketers who had focused entirely on the narrative that what is “natural” is always best. The marketers finally prevailed. When the national organic standards were issued in 2002, they were not based on science but rather on the naturalistic fallacy.
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2016 US Crops By Class

So here is the big picture. The only crop category for which organic yields were higher than the 2016 US average was for forage crops for feeding animals. To have produced all of the US agricultural output from 2016 as organic would have required more than 100 million more acres to have been farmed—an area greater than that of the entire state of California, the third largest US state. That amount of new land suitable for farming clearly does not exist in the US, and so that shortfall would induce more conversion of forest and grassland into farming in places like Brazil, leading to major releases of previously sequestered carbon in those soils

US Forage Crops 2016

There were higher yields for organic Hay and Haylage for animal feed in 2016, but for other animal feed crops, the organic yield was quite a bit lower. 17.1 million acres of alfalfa is grown for hay, mainly to feed dairy cattle. 1.71% of that land is in Certified Organic acres. Most of that land is much less productive.

Plant-based protein in an important component of the human and animal diet, but only relatively minor crops like pinto beans and Austrian Winter beans had higher yields as organic crops in the 2016 season. Nearly 2 million additional acres would have been needed to produce these crops as “Only Organic.” This is in spite of the fact that these crops require much less nitrogen fertilization, because they have an association with soil bacteria that fix atmospheric nitrogen for them in trade for energy.

Corn, soybeans and sorghum grown for grain accounted for 50% of all US crop acres in 2016. These crops provide most of the feed and biofuel for the US, as well as many major food ingredients. To have produced these crops as organic would have required 77 million acres to be farmed, something that would drive major land use conversion in places like Brazil and the associated climate and biodiversity impacts of that change.

Small grains are a major part of the human diet. With the exception of the relatively small crop rye, these plants do not yield very well in organic systems. To have supplied the domestic and important global market for these grains as organic would have required 33 million more planted acres, an area comparable to the entire state of Arkansas. Since many of these crops have quality issues associated with where they are grown, there really aren’t places in the US or the rest of the world where this could happen.

The only vegetable crop for which organic yields were higher was sweet potato. Organic represents 4.9% of total vegetable acreage in the US – much more than the overall 0.5% for all crops. Since many vegetable crops do best in specific climatic zones, that significant current organic footprint probably serves to raise overall prices for consumers, even if they do not purchase organic. When that issue is added to the fear of pesticide residues on vegetables driven by the Environmental Working Group’s “Dirty Dozen List,” this only contributes to the missed health advantages of vegetables in the diets of many consumers.
To have produced all the 2016 US grown vegetables as organic would have required 1.75 million more acres to be grown—something clearly not possible.

Tree nuts are considered to be a very healthy component of the diet, and may even reduce overeating that causes obesity because they make consumers feel full. These crops only flourish in certain climates, so there is no possibility that they could all be raised as organic. That transition would require 1.5 million more acres to be dedicated to those crops.

Organic yields of small fruits are often much lower than the national average. This is particularly true for strawberries, cranberries and wild blueberries. The one exception is tame blueberries, mostly in Washington state. To have produced all of this healthy fruit as organic would have required 238,000 more acres, which simply do not exist in areas with a suitable climate. In the case of strawberries, if the 11.6% of that valuable coastal land had been grown conventionally, there would have been 194 million pounds more strawberries available to consumers, probably at a lower price.

Organic makes up 2.61% of the land used to grow tree fruit and grapes. To produce all the fruit as organic would require a half million more acres of land. The organic vs. conventional citrus crop data is complicated by whether the crops are grown in California or Florida, where a devastating invasive bacterial disease has dramatically reduced yields. The best hopes for the future of the California industry depend on mostly non-organic pest control solutions.

Organic Tobacco constitutes 3.1% of the total acreage of this cancer-causing crop. Hops production, which is a booming industry these days for craft beer brewing, is 1.3% organic. Sunflower, which is the most significant crop on this list, is planted on 2.7 million US acres, and an additional 1.1 million acres would be required to produce it as organic.
Most cotton production has shifted to India and other places in Asia and Africa, because it is one of the very few crops grown in those regions with big grower benefits of insect resistance and herbicide tolerance. Still, there are 9.5 million US acres grown and it would take another 1.5 million acres to produce this important fiber crop as organic.
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So the good news is that organic remains a tiny part of US agriculture. The not so good news is that for key healthy fruit and vegetable crops, these antiquated farming methods are enough of a factor to raise the prices for even those who don’t buy organic.
Eliminating organic agriculture would not be nearly enough to help with climate change mitigation, but some alternative marketing category that would reward growers who practice the best kind of climate-friendly farming, those who utilize no-till methods and cover crops for instance, could make a real contribution. As consumers, our most climate-responsible buying behavior should be to reject organic and its false narratives.
Steve Savage is a plant pathologist and senior contributor to the GLP. Follow him on Twitter @grapedocHis Pop Agriculture podcast is available for listening or subscription on iTunes and Google Podcasts.
This article has been adapted from a presentation given by Steve Savage titled Care About Climate Change. Don’t Buy Organic and has been reproduced here with permission.
The GLP featured this article to reflect the diversity of news, opinion and analysis. The viewpoint is the author’s own. The GLP’s goal is to stimulate constructive discourse on challenging science issues.

Friday, October 4, 2019


(This piece was originally posted on the POP Agriculture Podcast 9/19/2019)

The Tardis (photo by  Zir, Wikimedia Commons )
The Tardis (photo by Zir, Wikimedia Commons)

The show has been running on the BBC since 1963, and part of what makes that long run possible is that the Doctor has the ability to be re-born from time to time with a different human body (although supposedly with two hearts).  There have been 13 different stars playing the part of The Doctor, and the most recent one is Jodie Whittaker (#13), the first female. I just finished binge watching that season to catch up! Other recent leads have been David Tennant (#10), Matt Smith (#11), and Peter Capaldi (#12).

Hard core Doctor Who fans call themselves “Whovians,”   The Urban dictionary puts it this way:  A few easy ways to tell if someone is a Whovian are: Turn off all the lights while repeating "Hey, who turned out the lights?", moving statues around while they aren't looking or telling them not to blink while staring at a statue, yelling exterminate at them in a freaky as hell robot voice, and watching how they react. If they start screaming they're most likely a Whovian.” 

So, what’s the “exterminate” thing about?  There are new and different “bad guys” for the Doctor to out-wit in most episodes, but throughout the years of shows, a frequent “threat to the future of humanity” has been a strange race of robotic space beings called the Daleks.  Back in the earliest, obviously low budget days of the show, the Daleks looked a lot like modified trash cans (I guess “dust bins” since it’s British) with toilet plungers for arms.  That basic, funky, Daleck look has been preserved over the history of the show as has that creepy chant that of theirs: “Exterminate! Exterminate! ….” 
Dalek image by Nelo Hotsuma from Rockwall [CC BY 2.0 (]
Dalek image by Nelo Hotsuma from Rockwall [CC BY 2.0 (]

So the Daleks of Dr. Who are a classic example of fictional, pop-culture aliens who are out to exterminate humans. There are also many examples of pop-culture stories of humans trying to “exterminate” some sort of alien invaders.  On today’s POPagriculture podcast we are going to talk about a real world story about how humans successfully managed to “Exterminate” some alien invaders who were threatening the grape industries of California.

Standard Intro

So, in California there are lots of farmers who tend 880,000 acres of grapes.  These include those that are specifically for drying to make raisins.  Other grapes are grown as a nice, fresh, mostly seedless snack.  Throughout the state there are also various “appellations” for wine grape production.  Together these crops bring in about 5.8 billion dollars a year to the state’s economy. These products are loved by not just Americans but by people around the world.  California has nearly ideal climatic conditions for each of these grape categories, and since they are relatively drought tolerant they are a good fit for our limited water resources.  One nice thing is that we don’t have much rain during the summer and so we don’t have to deal with some difficult fungal diseases that are a big challenge in places like Europe.  There are still certainly pests that have to be dealt with, but the grape industry has always been a leader in doing that is a sustainable way.

Lobesia:  European Grapevine Moth image by Jack Kelly Clark , University of California Extension
Lobesia: European Grapevine Moth image by Jack Kelly Clark, University of California Extension
So that’s the background, but the drama for our story began in the summer of 2009 in a famous, premium wine grape-growing region called the Napa Valley.  One of the growers there spotted a caterpillar munching away on some of his grapes.  Now there are several kinds of moths that can be pests of California grapes, particularly during their larval stage as caterpillars.  But the grower noticed that this one didn’t look like those familiar types. Being suspicious he sent a picture to a county extension agent – a kind of University employee whose job it is to support the industry with research and advice.  It turned out that was a new kind of moth to California – an alien invader!  Ok, not a space alien, but scary from the perspective of grape farmers.  It was called the European Grapevine Moth or “EVGM.” As its name implies it has been a pest in that continent for a long time.  That name doesn’t sound scary enough for our story so lets use the scientific name, Lobesia botrana.

Now the thing is that this wasn’t just another moth.  The caterpillar stage of this bug would do a lot more damage to the grape clusters than the other moth species and that would mean nice things like “frass” or insect poop on the grapes or later the raisins.  To make matters worse, the feeding opens the way for fungi that rot the grapes and that kind of infection can spread from berry to berry throughout the cluster.  This would make it a lot harder for the raisin growers to have a high quality product, it would mean a lot more food waste even all the way to the consumer level for the table grapes.  Moldy grapes definitely don’t make for high quality wine!

Rotting grape image by Andrea Lucchi , University of California
Rotting grape image by Andrea Lucchi, University of California


Now of course there wasn’t an extraterrestrial “Doctor” to lead this campaign, but even Dr. Who drafts a team of regular humans to help defeat the aliens.

In this case the team comprised representatives of the grower communities, university experts and government employees from the relevant state and federal departments. They held an emergency meeting and decided that they wanted to see if they could come up with a way to not only stop the spread of the pest, but if at all possible to completely eradicate it from California.  Eradicate! Doesn’t sound quite as harsh as “exterminate!” but it’s essentially the same idea.



In order to see what they were up against, sixty thousand “Sticky traps” were distributed state wide at a density of 39 per square kilometer in vineyards and 10 per square kilometer in residential areas. In the next 2010 growing season they found 100,000 moths in several California counties.  This was going to be a big challenge!  Only a comprehensive strategy with broad participation would give any hope of winning.  So the team developed a multi-prong strategy:


Those sticky traps continued to be used to monitor progress, but they were careful to use red colored traps because they are much less likely to accidentally trap honeybees.


It was important to find ways to limit further spread of the aliens. The adult moths can fly, but they don’t tend to fly too far as long as they can find the grapes they want. Quarantine rules were set up to prevent fruit, farm equipment, recycled fence or grape posts, or other things that might allow the pest to hitch-hike long distances. It turned out that the moth larvae could survive the stemming and crushing and even pressing of wine grapes – so it was critical not to move around those by-products of the winemaking process.


They also used an approach called “pheromone confusion” that was set up on an area-wide basis where the Lobesia had been found.  This involves putting up emitters of the specific sex hormone for this moth so that the males are getting so many “scent trails” that they rarely actually find a female to actually mate. 


There were lots of outreach programs to get everybody up to speed on the situation and to know their role.  This included grape growers, wineries, and fruit or raisin packers, and pest control advisors. The outreach also had to include on the order of 3,000 homeowners because they also needed to cooperate, especially if they had backyard grapes, as many did. The coordinated task force would help those owners to treat their grapes or remove their fruit so that they didn’t become a reservoir to then fan out into the commercial vineyards. Not only were there public meetings to reach all these groups, there was a Facebook page and a website at


The researchers developed a sophisticated “degree day model” to predict when each of the 3-4 new generations of moths would be coming out so that insecticide sprays could be timed just right, not only to protect the crop, but to prevent the moth numbers from really blowing up as they would if not strategically checked this way.  Almost all of this spraying was done on a voluntary basis at the grower’s own cost.  In Napa and Sonoma in 2012 the growers treated more than 12,000 acres.  The organic growers also sprayed using the insecticide options that are allowed under their rules.  


The combination of the quarantines, the pheromone confusion and the well-timed insecticide sprays achieved what is called an “allee effect” in population biology lingo.  This is when the population size gets down to the point where there are too few of the pests in a given area to successfully mate.


Historical progress  towards eradication of EVGM from California. University of California.
 Historical progress towards eradication of EVGM from California. University of California.

This massive, voluntary, cooperative effort was highly coordinated across the different counties of the state and it began to pay off.  In 2011 there were 2,335 acres quarantined because of the presence of the moth.  By 2014 that number was down to 446 acres.  By 2016 the pest was officially declared to have been eradicated.

Figure 2 Victory Lap! (University of California)
Victory Lap! (University of California)



In the Dr Who shows the Daleks don’t ever seem to manage to “eliminate” humans, but in this story the humans managed to “eliminate” the alien pest. 


There have been some other historical examples where the humans were able to “exterminate” a new insect pest.  Another strategy that was used in some of these battles was the intentional release of sterile males of the pest species so that they so that they would out-compete the wild males trying to breed with the wild females.  This helped when the Mediterranean Fruit Fly came to California several times over the years.   


Another pest eradication success story had to do with a pest of cotton called the Pink Bollworm.  In that case in addition to the release of sterile males, pheromone confusion, area-wide “plow downs” and strategic sprays, the growers also had the opportunity to use lines of “Bt cotton,” genetically engineered to be resistant to the pest. 


Now unfortunately, it will never be possible to have this sort of victory over all the pests of grapes or any crops for that matter.  Still, when growers are only up against a familiar set of pests, they can achieve a sufficient degree of control to protect their livelihood, keep food affordable, and prevent the pest-related quality or food safety problems that would otherwise flow on down to the consumer level.








Thursday, October 3, 2019

A Plant Murder Mystery

(This Blog was originally posted as a Podcast/blog on the POPAgriculture website on 9/5/19)

For some reason, our culture seems to be fascinated by a good murder mystery. I think we all believe that murder is a horrible thing, but we love a story about “good guys” solving a murder case using smarts, careful observation and maybe a little luck. Then we can celebrate when they finally crack the case. “In Cold Blood”, Truman Capote’s book on the 1959 murder of a family in Kansas, played a large role in the growth of the true crime genre. The podcast, Serial, kicked off the most recent true crime renaissance, paving the way for many other true crime podcasts as well as series and documentaries like Netflix’s “Making a Murderer” and HBO’s “The Jinx.” And, who can discount the influence the show “Law & Order” has had, fueling our appetite for stories “ripped from the headlines”?  But what about plants? Can they be murdered? Well there certainly are cases where people “murder” plants in a way that is bad, like deforestation.

Image of deforestation by  Vera Kratochvil . Actually, this was originally a pest-based mass murder – bark beetle infestation.

Image of deforestation by Vera Kratochvil.  Actually this was originally a pest-based mass murder – bark beetle infestation (purchased image)

But plants are most often murdered by other organisms from nature that we call “pests.”

I was originally trained as a “plant pathologist” and we are the folks who study the diseases of plants. My graduate work was with diseases of grapes, hence my Twitter handle, @grapedoc. Well, plants, including grapes, can sometimes mysteriously die. On today’s  episode, I want to talk about an alarming new disease of grapes that arose in the 19th century. It took a  long time for scientists to track down the culprit. For decades, the “murderer” couldn’t be identified and what was happening in American vineyards really was a case of serial killings whose trail ran cold. A couple of weeks ago, I had a chance to meet another plant pathologist who was one of the key “detectives” who finally “cracked the case” of the mysterious deaths of grapes. He was a player in a great story that I’m happy to be able to share with you today.

When Europeans began to colonize North America 400+ years ago, they brought along the crops they knew how to grow so they could have food – things like wheat, barley, apples, and grapes. Over time, they also adopted several kinds of plants that were unknown in the “Old World” like potatoes, tomatoes, corn and blueberries,  which were also taken back to Europe. Back to the settler’s familiar crops - some did well in the New World, but others didn’t. Wheat did great in the Northern Colonies, but poorly in the South because of a fungal “rust” disease favored by the wetter, warmer weather there. The winters in the North were too cold for one of the European’s favorite crops – grapes. When the settlers tried to grow grapes in the South they would grow for a while, but then mysteriously die after a few years.

The Anaheim vineyards would have been "head-trained" like this rather than the modern system of trellising ( Image from UC Davis ).
The Anaheim vineyards would have been "head-trained" like this rather than the modern system of trellising  (Image from UC Davis)

The Spanish brought the first grapes to the New World. The Friars that set up the first set of missions in what would become California needed the grapes to make wine for communion. The grapes thrived there because of the “Mediterranean” type of climate which was much like that of Spain or Italy or parts of France. For a long time, the grapes did well, but then in the late 1800s they began to mysteriously die, particularly in the Anaheim area. Of course, that is a city today and the home of Disneyland, but it started out as a farming community. There is a newspaper article about these mysterious vine deaths that you can see online from “The San Francisco Call” from December of 1894 about what had come to be called “Anaheim” disease. It describes how over a period of 10 years the strange malady had ravaged over 20,000 acres of grapes and nothing the growers did seemed to help. Anaheim has also been the scene for some human disease incidents, like the 2017 outbreak of Legionnaire’s disease that was linked to those who visited Disneyland. But the 1894 article was quoting a talk given by the head of the State Viticultural Commission, E.C. Biehowsky, in which he was celebrating the fact that the disease seemed to be abating although no one knew why. But the case of vine deaths remained unsolved and there were other outbreaks that killed vines in the 1930s and 1940s. This eventually drove the grape industry out of Southern California and into other parts of the state.

Back in 1892, California’s first professional plant pathologist, Newton B. Pierce, tried to unravel the mystery of this disease. He suspected that it was caused by a bacterium but he wasn’t able to culture any and use them to replicate the disease – the protocol called “Koch’s Postulates” that is the required way to provide proof of what kills or sickens something in the “courtroom” of science. Others ended up naming this malady “Pierce’s Disease.” That’s not a great outcome. I hope they never name some deadly plant disease after me!

The next “detective” on the case was Bill Hewitt at the University of California, Davis. He showed that the disease could be transmitted from one vine to another by grafting and that, in nature, the disease was spread by little sap sucking bugs called blue-green sharpshooters. This fit the M.O. of a virus and that would also explain why you couldn’t culture it. Suspect #2, a virus. Then, a competing set of detectives in Florida showed that the disease could be suppressed a bit with the antibiotic tetracycline. That made them suspect it was a mycoplasma – effectively the third “suspect” in this case. One of those researchers at the University of Florida is Don Hopkins and he is the actor from this story that I recently met. The Florida group’s suspicion about a mycoplasma was shared by a grapevine virus expert at Davis, named Austin Goheen, because he showed that heat could also suppress the disease.

Dr. Don Hopkins from the University of Florida (right) and Sonoma County grape farm advisor Rhonda Smith (left). We spent two days planting the young grapevines pictured here for a Pierce's Disease biocontrol trial this summer.
Dr. Don Hopkins from the University of Florida (right) and Sonoma County grape farm advisor Rhonda Smith (left).  We spent two days planting the young grapevines pictured here for a Pierce's Disease biocontrol trial this summer
Now, the classic meme for a detective show is someone with a magnifying glass. That might be enough enlargement power for someone working on a homicide case, but the detectives in the plant murder investigation needed something a lot more powerful. Fortunately, there was a powerful new investigative tool that was becoming more available called an electron microscope. The earliest work on this tool was in the early 1930s and it became more practical with work at the University of Toronto in 1938. With this new tool, scientists were able to see far smaller things than had been possible with even the best light microscopes. A researcher at Davis in the 1960s and early 70s named S.K. Lowe assisted Goheen and another scientist named George Nyland, using her skill with the department’s new electron microscope. With it, they peered inside the grapevine to see if they could catch the perpetrator of Pierce’s disease in the act. Inside the plant’s xylem cells – essentially its water plumbing system - they saw strange, elongated blobs which they decided to call “Rickettsia-like organisms,” the fourth suspect in the case. They also described it as a “fastidious bacterium” because it was apparently too picky to let people grow it on normal culture media. Goheen, Nyland, and Lowe got a paper describing this new finding accepted for publication in a journal called Phytopathology on October 3, 1972, but it didn’t actually publish until March of 1973.
The image of the "culprit" taken with an electron microscope and published in the journal Phytopathology. 
The image of the "culprit" taken with an electron microscope and published in the journal Phytopathology
Simultaneously, the Florida team, Hopkins and Mollenhauer, published similar findings in the January 1973 issue of the prestigious journal, “Science,” also based on what they had been able to see using an electron microscope. They also classified the suspect as a “Rickettsia-like bacterium.” For both investigations, those electron microscope images were “the smoking gun.” Even though these two sets of “detectives” on opposite sides of the country fingered the same culprit, there was actually somewhat of a rivalry. In a sense, the Florida team “won” because their verdict came out in print two months earlier! (Remember this was long before the internet.)

By the time I got to that UC Davis plant pathology department in the spring of 1977, George Nyland had retired, and my new major professor was the replacement for Bill Hewitt. Austin Goheen was still there but would retire within two years. Since I was in the “Grape Lab,” I certainly heard the UC Davis version of the tale of hunting down the culprit for Pierce’s disease, and they were still just calling it a Rickettsia-like bacterium.

Then in 1978, another team of scientists/detectives at a different campus of the University of California in Berkeley finally caught the culprit red handed by coming up with a recipe for the medium which would finally coax this picky perpetrator to grow in their petri plates. These new players were Mike Davis, Alex Davis, and Sherman Thompson. They found the same organism also caused almond leaf Scorch disease. So, the “suspect” was now “identified”, but we still didn’t know exactly what to call it.

It wasn’t until 1987 that yet another team of six “detectives” used the rapidly advancing tools of biotechnology and DNA/RNA sequencing to “fingerprint” the grape murdering bacteria, and they declared it to be a brand new genus, which they gave the clever name Xylella fastidiosa:  Xylella for the Xylem of the plant in which it lives, and fastidiosa in acknowledgement of how challenging it had been to learn to grow it outside of its unfortunate victims. This diverse team of scientists came from labs at the USDA, Rutgers, the Weyerhaeuser company, the University of Illinois, and the Centers for Disease Control, or CDC. Add that to the three other institutions in this story and you get a sense for how hard it was to fully understand this disease that had been killing grapes since those early days in Anaheim, or the even earlier attempts to grow grapes in the American Southeast, which turns out to be where the bad guys came from in the first place. In the text version of this episode on, you can also see a map of where this bad bacterium can now be found around the world – mostly in the Americas, but a bit in Europe and Asia.
he tragic death of an old olive grove, "murdered" by Xylella (Sjor,  Wikimedia commons ). 
It turns out that Xylella isn’t just guilty of killing grapes. It can cause problems for oaks, citrus, and the ornamental oleander which is widely used for planting in the median strips of California highways. Just recently, a new and unique strain of Xylella showed up in Italy where it “murdered” trees in venerable old olive groves. I’ve provided a link to a “National Geographic” article about this – it’s so sad to think about some of those ancient trees going down. It’s a threat to olives in Spain and Greece as well.

The tragic death of an old olive grove, "murdered" by Xylella (Sjor, Wikimedia commons)

aerial over Sonoma.jpg
A picture I took this summer while flying into Sonoma County. 
Note the missing (murdered) vines by the river
But just knowing the true cause of Pierce’s disease didn’t make the problem go away. You can’t exactly go out and arrest bacteria that live, as it turns out, in all sorts of plants – cultivated and wild. What the grape industry had learned was that the bug that spreads this malady – the blue-green sharpshooter - only likes to live and feed on the plants that tend to grow along rivers in what are called “riparian habitats.” The sharpshooters venture out into vineyards from time to time, so the typical pattern is you see dying vines in the parts of vineyards closest to the Napa River in Napa county, or the Russian River in Sonoma county.

There is an aerial photo above that I recently took while flying into Sonoma. You see that there are more missing (killed) vines on the side of a vineyard along the river but not as many near the reservoirs which don’t have a true “riparian” zone. No one would consider taking out that natural vegetation in the riparian zone although there can be state funds to selectively take out certain invasive plants which are actually even worse than the native ones in terms of being a hiding place for the bacterium and its vector.

Grape growers in these regions mostly just deal with a certain degree of vine death because these are regions with a great reputation for wine quality.

But there is a twist in our murder mystery! In 1997, there was a dramatic die-off of grapevines in a relatively new wine grape growing region called the Temecula Valley. This is in southern California, but further inland than that original problem zone in Anaheim. Temecula Valley had not had any problems with Pierce’s disease because it’s pretty much a desert and does not have those “riparian” zones that the blue-green sharpshooter accomplice likes. But a few years earlier, probably because of some eggs on nursery stock imported to California from the southeastern U.S., a new invasive insect had arrived called the glassy winged sharpshooter.

The "accomplice" (Glassywinged Sharpshooter, image from the  California Center for Invasive Species Research ).
The "accomplice" (Glassywinged Sharpshooter, image from 

Now our identified murderous Xylella had an accomplice that isn’t at all picky about what plants it feeds on. It’s happy on citrus and there was a lot of that in Temecula intermixed with the vineyards. Some of the wineries lost 80 to 90% of their vines in the first few years of this attack and it seemed like the end of grapes, not just in Temecula, but potentially throughout the state if that new insect would spread.

The grape industry and its supporting government agencies quickly mobilized to fight this dangerous new duo. They found an insecticide that could be given to the roots of the citrus and grapes through the drip irrigation system. It would then move up and protect the plant from the sharpshooters. That put the brakes on the epidemic and the vineyards of Temecula have been successfully replanted and protected. I visited grape growers in that area in July and they have almost no dead vines and a thriving tourist industry for wine tasting.

The state also put in place very rigorous inspections and quarantines of all nursery stock moving north to prevent the sort of hitchhiking that got the glassy wing here in the first place. Grape growers all around the state chip in for a state run monitoring and targeted insecticide program that has, thus far, been able to prevent that new accomplice from moving to the rest of the state. It’s working so far, but no one in the industry is complacent.

The search is on for additional tools to fight both the insect and the bacterium. It would take another whole podcast to just list the research efforts, but briefly they involve ideas ranging from conventional breeding, to biotech traits, to live biocontrol agents, to insect predators and parasites, to various natural products, to a new sprayable chemical bactericide. I’m tracking these now and am even participating in one effort as part of my “day job” as a technology consultant. I can’t think of anything I’d find more satisfying than to see the grape industry find a robust set of strategies to shut down that murderous bacterium once and for all!

Good general reference on PD including new Olive issues:

Big article Hopkins and Purcell 2002 – talks about host range, geographic …