Imagine saying goodbye to the entire citrus section of the grocery store.

Oranges, lemons, yuzu, and many other citrus trees are in danger.

Huanglongbing is a devastating bacterial disease that's decimating citrus crops across the U.S.

But there is hope.

Scientists, citrus growers, government officials, and backyard enthusiasts are all trying to come together to find solutions to stop its spread and fast.

And one group is closing in on that answer by using good bacteria to fight the bad.

This is Hungry Planet.

Let's dig in.

Picture a world without citrus.

That means orange juice is gone, and that's only the start.

No more tangy lime juice in your guacamole.

No more yuzu cocktails or lemon curd spread across a scone.

No more kumquats, or grapefruits, or pummelos.

Huanglongbing or HLB could make this a reality.

It's a bacterial disease spread from tree to tree by a tiny insect called Asian Citrus Psyllid.

After HLB infects a tree, the tree develops blotchy modelled leaves.

The fruit becomes misshapen, green and bitter, and it can just fall off the tree early.

Once HLB appears, it can start spreading to the rest of the grove in just a few weeks.

If not handled quickly, trees can die within months to a few years.

In its first year in the U.S., it destroyed over 100,000 acres of citrus groves in Florida--about 13% of the state's crop.

And that could have rippling effects not just in cuisine but in culture too.

Citrus shows up in culinary, medicinal, ornamental, and religious practices.

From eating pummelos during Chinese New Year to setting up a lemonade stand on the first hot summer day.

We ask citrus to play many roles in our lives.

And this wide diversity of uses mirrors that wide diversity in citrus itself.

-Alrighty, cheers, -Cheers.

-It's actually pretty good.

-It's delicious.

Yeah, it's not too sweet.

And this one ever never gets very sweet.

(Niba) This is Christopher Drozd, a scientist at UC Riverside who's looking at the microbiomes of citrus trees to try and protect groves from HLB; and Dr. Tracy Kahn, the curator of the UC Riverside Citrus Variety Collection.

(Tracy) This collection is one of the world's most diverse collections of citrus and citrus relatives.

This is called Australian finger lime is its common name, but its genus name is micro-citrus.

My husband thinks that they look like coyote turds, which isn't very salable, but if you open up and you can see the juice vesicles are growing out as we speak.

(Niba) Citrus varieties range from sour lemons to sweet oranges to bitter grapefruits.

But they also include finger limes, which are small fruits bursting with tiny bubbles of juice like a citrus caviar, and buddah's hand, a dense fruit with finger-like projections and a sweet delicious smelling rind.

Even the hard, gooey bale fruit with a resinous interior.

-Doesn't taste very good.

-No!

I thought it was gonna be juicy!

-Is it super sour?

-It tastes like tree sap!

Pretty much every commercially produced variety of citrus is susceptible to HLB and can be killed by this disease.

HLB first showed up in Asia in the early 1900s.

It then spread around the globe through India, Brazil, and other countries before showing up in the U.S., in Florida, in 2005.

It's been spreading across the country ever since.

Starting with Louisiana, Georgia, South Carolina, and now reaching as far as Texas and California.

(Christopher) So HLP is transmitted by the Asian citrus psyllid, which is an insect that's about the size of a grain of rice.

And these insects are reservoirs for this disease.

So they carry this disease within them, they pass it on to a tree, they lay their eggs on that tree than their larva hatch, feed on that tree, pick up the disease again and then turn into adults and continue out the cycle throughout an orchard or an environment.

In places like Florida where it's endemic, they have an unusual approach that involves injecting trees with large amounts of antibiotics to try and kill this bacteria within the tree.

We don't really know what the consequences of that would be long term in the environment.

So we need different and new tools that can help us address this issue.

And this disease is so complex and so insidious that you really do need like a multi-pronged approach.

I was inspired to kind of get into this field of research because of my family's connection with agriculture.

My grandfather and grandmother bought a house in this rural part of California called La Habra Heights in the 1960s.

This property had avocado and citrus trees that they cared for, and they would sell the fruits in a roadside stand to supplement their income while raising a family of six kids.

And even though my grandfather has since passed, we still keep the tradition alive of harvesting all of the fruits from that orchard and donating them to local food banks through a distribution network called Food Forward.

Food Forward fights hunger and prevents food waste by rescuing fresh surplus produce, connecting that abundance with people experiencing food insecurity, and inspiring others to do the same.

(Niba) This is Allie Gialketsis, the Senior Manager of Community Programs at Food Forward, an organization that connects excess food to the people who need it in California communities.

(Ally) So we recover produce through our three food-recovery programs, which is backyard harvest program, our farmers market recovery program, where we're gleaning from 15 markets throughout Los Angeles and Ventura counties.

And our third program is the wholesale recovery program.

Food Forward partners with hundreds of agencies throughout the Southern California region and beyond.

And these agencies range from supporting communities that are low income families, or maybe senior centers, or the LGBTQ population.

All of these folks are experiencing food insecurity for a wide variety of reasons.

(Niba) In 2022, nearly a quarter of households in Los Angeles County were food insecure.

The majority of residents dealing with this were 18 to 40 years old, low income, female, and Latinos.

To cope with rising prices, many of them bought less or different lower-quality foods.

But local organizations are determined to make sure that no food goes to waste, even in HLB-stricken areas.

In places where HLB is a risk of becoming a permanent strain on the area like Southern California, organizations like the California Department of Food and Agriculture, or CDFA, give recommendations to citrus growers and backyard farmers on how to harvest and distribute citrus.

This includes strategies like removing the leaves and stems from plants to prevent the spread of both the insects and the bacteria they carry.

(Ally) We try to keep all of the produce that we collect, primarily fruits, in the communities that we're harvesting them from, from the Backyard Harvest Program.

So it really works well with HLB, because if we're harvesting an area that is kind of more prone to it, it's not leaving the area and going through an area that's less prone to it.

(Christopher) They're able to distribute all of these citruses within this quarantine zone to make sure that this pathogen doesn't spread to other plants, but we don't have to worry about it spreading to people.

This bacteria would-- does nothing to humans, doesn't affect us at all.

(Ally) It's really inspiring, addressing climate change and food insecurity.

And we're doing it in a way that's really simple.

We're taking stuff that would otherwise get thrown out and giving it to people who would otherwise not have it.

So it's it's a win-win on everyone's part.

There's so much negativity in the world, and doing this kind of work, you're interacting with people who are really motivated to help people and to reduce waste.

And I'm really grateful to be able to work in such a great community.

(Niba) Volunteers at places like Food Forward help reduce the food waste that HLB can create.

While scientists like Christopher work on solutions that target the disease itself.

Just like humans, trees are covered in bacteria, forming their own natural microbiome that helps keep them healthy.

Christopher hopes to find good bacteria that can help protect trees from HLB.

(Christopher) Previous research from our lab has shown that certain microbiome members are associated with less severe symptoms, even when the tree has been infected for a long period of time.

And so this motivates us to better understand the tree microbiome and to understand what each member might contribute to overall tree health.

(Niba) Scientists found that trees with different microbiomes may be differently affected by HLB infection.

So researchers like Christopher are working to figure out which parts of that microbiome are protective against HLB.

Because if they find protective bacteria, they could use them to fight the disease.

The bacteria that's associated with this disease is nearly impossible to grow in the lab.

So we have to use a close relative that is able to grow in a Petri dish environment to understand how other bacteria might interact with it.

This is where we test whether or not the bacteria that we isolate from the environment can antagonize the closest culturable relative to the pathogen associated with HLB.

So you're testing how the bacteria interacts with the HLB to see if it's doing nothing or if it's slowing the growth of HLB?

Exactly, yeah.

And so we can see it through the clearing of growth.

So when we want to test whether or not other bacteria can inhibit this bacteria's growth, and hopefully the one that causes HLB, we'll look at plates like this.

And we'll look for these zones of clearing.

It's very clear right here-- you can see that these four bacteria have these little halos where they are either producing a chemical, or taking up some sort of nutrients that are preventing the other bacteria from growing.

One of the things that we do in our lab is we try to understand what molecules might be responsible for that interaction to try and develop new tools that aren't, you know, potentially medically important antibiotics.

We look for these other molecules that we can identify and develop.

(Niba) So eventually, once you've figured out which bacterium in which molecules are inhibiting the growth of HLB, what's going to happen then?

(Christopher) Hopefully, an agrochemical company would pick it up and sort of develop it for use in the field.

Another alternative is to just inoculate the bacteria directly into the trees, and the tree would have an organism then producing this molecule.

Or if this molecule isn't too intense and complex, labs can actually engineer the tree to produce the molecule naturally.

Even if it is something growers would have to apply, it's better than you know, the one tool we have now, which is the antibiotic.

HLB is a huge threat, and the only way to win these kinds of fights is to work together.

This means cooperation between lots of different groups-- scientists, backyard gardeners, farmers, policymakers, and maybe even some good bacteria.

(Christopher) It's definitely really urgent.

This isn't like just some problem we've had forever that, you know, we knock around and fix with all these different ways, but this is kind of a new problem that needs new solutions.

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