Spinach Genes, Ladybugs, and Pesticides: The Cocktail That Might Save Orange Juice

“People are either going to drink transgenic orange juice or they’re going to drink apple juice,” a pessimistic University of Florida scientist was quoted saying in The New York Times. It’s not that the farmers are pushing for higher yields or glowing fields; it’s just that there’s a bacteria spreading through Florida that is killing orange trees, and nothing on the orange family tree is equipped to fight it.

Since showing up in the US in 2005, the citrus greening disease huanglongbing—often referred to as HLB—has infected about half of trees in every citrus orchard in Florida. The disease causes the fruit on the tree to develop unevenly, stay green, drop from limbs and rot. According to Erik Mirkov, a Texas plant pathologist who has studied the disease, “Citrus greening is a bacterial disease that affects the vascular system of the tree, or phloem. It basically shuts off the tree’s ability to take up and use water and nutrients, causing the tree to die.”

As there’s no cure—and in all of citrus, no immunity—HLB is a threat to the survival of Florida’s $9 billion citrus industry, the source of 80 percent of America’s orange juice. So the US Department of Agriculture, along with juice growers, are funding research to do what nature couldn’t: genetically modify their way to an HLB resistant plant.

The early front-runner for the role of viable gene donor is the humble spinach plant. Plant pathologist Mirkov has been working on a hardier orange tree since the last orange blight—citrus canker—was threatening America’s juice supply back in 2005.

Mirkov wanted to limit himself to taking only proteins that people were already eating, and noticed that spinach proteins were resistant to a broad spectrum of bacteria and fungi, and he transferred two genes from spinach to citrus trees, creating a transgenic, resistant plant.

“We injected canker into the leaves of transgenic plants with one spinach gene and found that the bacterial lesions didn’t spread,” he said. “But we also showed that transgenic plants infected in the rootstock with citrus greening disease flourished and produced lots of leaves, while the non-transgenic trees produced just one leaf.”

The process for testing out the safety of a transgenic tree is long and expensive, so don't start eyeing the juice aisle suspiciously just yet. When covering HLB, both the Times and The Washington Post noted that consumers, and by extension farmers, are uneasy with drinking a big glass of GMO. But if the disease is incurable, what other options are there?

You can always try to hit it right in the vector.

The invasive HLB bacteria are transferred from tree to tree via the also-invasive Asian citrus psyllid, a small insect from the family of “jumping plant lice,” which was first detected in America in 1998. When the psyllid feeds on the leaves of infected trees, it acquires the bacteria, which is then transmitted to healthy trees when the psyllid flies over and feeds on them afterwards.

While some bacteria feel unstoppable, we have lots of options for killing bugs. In India, farmers have somewhat slowed the psyllid, and therefore HLB, by spraying insecticides, which American farmers are also trying.

The other option is fighting one invasive species by bringing in another. A type of small wasp, Tamarixia radiata, from India was deliberately introduced to Florida groves. The wasp is an ectoparasitoid, which means it’s one of those wasps that lays its eggs on a psyllid, so when the larvae hatch, they have a nice meal waiting for them. It’s grim (videos of the process are utterly disgusting and cannot be unseen), but it’s also been proven effective. When the wasp was introduced to the HLB-stricken groves of Reunion Island in 1978, it revived the citrus industry there. For whatever reason the wasps aren’t as parasitic in Florida, and part of the problem is that there is actually adorable competition to eat the invasive psyllids.

Ladybugs are one of everyone’s favorite bugs, but coccinellids like the ladybug, are actually vicious predators on a tiny, tiny scale. Gardeners love them because they eat aphids, and fortunately for orange farmers, they also eat the aphids’ close relative, the psyllid. Unfortunately, they eat them fairly indiscriminately, including when the psyllid is still being eaten from inside by a wasp larvae.

It’s sort of a perfect metaphor for the clusterfuck of modern agriculture that’s happening in Florida: an invasive species is killing the plants, so another invasive species is brought in, and insecticides that are used to kill the former also kill the latter, on top of which, you’ve got ladybugs killing them all.

So that’s why that scientist thinks it's coming down to GMOs to save orange juice.