AskScience AMA Series: I'm a plant virologist from the University of Maryland! I study how we can use plant viruses to combat citrus greening, a lethal disease that attacks citrus trees. No cure means citrus will disappear from supermarkets in a decade! AMA about citrus greening and plant virology!

https://www.reddit.com/r/askscience/comments/1j81y3z/askscience_ama_series_im_a_plant_virologist_from/

created by AskScienceModerator on 10/03/2025 at 15:57 UTC*

316 upvotes, 21 top-level comments (showing 21)

Hi Reddit! I am a professor in the University of Maryland’s Cell Biology and Molecular Genetics Department. I study plant viruses and examine how we can use them to help stop citrus greening disease, which has wiped out hundreds of millions of citrus trees in the U.S. and worldwide. Citrus greening is spread by tiny insects called psyllids, which inject disease-causing bacteria into a tree’s vascular system. My lab along with the company that I co-founded, Silvec Biologics, have developed an approach to combat this disease by infecting trees with a virus that delivers antibiotic agents to the location where the bacteria live.

Ask me all your questions about plant virology and citrus greening! I’ll be on from **1:30 to 3:30 p.m. ET (17:30--19:30 UT) on Wednesday, March 12**.

Anne Simon is a professor of cell biology and molecular genetics at the University of Maryland. Her lab uses small plus-strand RNA viruses to study how viruses move and infect plants. She is trying to understand how infection by some viruses makes the plants more receptive to infection by other pathogens.

Anne's work has attracted the attention and financial support of leading institutions, including the NIH, USDA and NSF, and her expertise was tapped by Chris Carter, creator of the cult favorite television series "The X-Files.” Anne served as science adviser for the series and received story writing credit for the popular episode, “My Struggle II,” which aired in 2016 and allowed her to share her knowledge and passion for virology with millions of fans. She is also the author of the book “The Real Science Behind The X-Files”.

Anne received a B.A. in biology from the University of California, San Diego, and a Ph.D. in genetics from Indiana University. She was elected fellow of the American Academy of Microbiology in 2014.

Comments

Comment by DeliciousPumpkinPie at 10/03/2025 at 16:26 UTC

15 upvotes, 1 direct replies

Not specifically about citrus greening, but how common is it for plant viruses to “jump” hosts? Like if there’s a virus that specifically infects, say, brassicas, is it possible or likely that it could also start infecting, say, nightshades? What would have to happen for that to be a thing?

Comment by SubstantialPressure3 at 10/03/2025 at 16:34 UTC

21 upvotes, 1 direct replies

Several articles I've read say that planting marigolds in the same area as other plants will disrupt certain plant viruses that spread through roots/soil.

What is it about the marigolds that disrupt those viruses and how does that work?

How can home gardeners prevent citrus greening on our trees?

Comment by GaySasquatch at 10/03/2025 at 17:02 UTC

9 upvotes, 1 direct replies

If we are to start using genetically modified viruses for plant cellular and gene therapy, we will need to find a suitable virus that offers infectivity through a wide range of species. Which plant virus is currently seen or used as the best candidate? Is there something analogous to AAV for cell and gene therapy in humans? What considerations are needed for plant and cellular gene therapy across species, or plants that have different physiological pathways, such as conifers vs. Deciduous trees?

Comment by alpacalypse-llama at 10/03/2025 at 17:14 UTC

6 upvotes, 1 direct replies

Do plants/trees have something analogous to an immune system? If so, how does it compare to our immune systems? Aside from disease-carrying insects, how else do viruses spread? Is there something analogous to norovirus for plants where they can catch an infection from how the virus affects the plant (ie norovirus can cause diarrhea which can further spread the virus)?

Thank you in advance!

Comment by Roguewolfe at 10/03/2025 at 20:14 UTC*

6 upvotes, 1 direct replies

Is there a concern that the pathogenic bacteria within the tree's vasculature will develop resistance to the virally-produced antibiotic?

Are you designing viruses that produce multiple types of antibiotic particles at once (or multiple viruses variants to that same end)?

Lastly, are the viruses using the host plant's ribosomes or the invasive bacteria's ribosomes to manufacture the antibiotic?

Comment by teridon at 10/03/2025 at 16:41 UTC

4 upvotes, 1 direct replies

To what extent does the size and variation of plant genome affect your work? I've read that some plants are polyploidy, and that the DNA in the nucleus is different than that of organelles and chloroplasts. Which part of the plant cell does the virus you use infect?

Comment by ElMondoH at 10/03/2025 at 17:06 UTC

5 upvotes, 1 direct replies

The Wikipedia article on HLB notes:

"Further expansion of medically important antibiotics (to combat HLB) is proposed by the EPA but opposed by the FDA and CDC, primarily as antibiotic resistance can be expected to develop and affect human health."

... and the two linked articles - NYTimes[1], biologicaldiversity.org[2] - go into further detail.

1: https://www.nytimes.com/2019/05/17/health/antibiotics-oranges-florida.html

2: https://www.biologicaldiversity.org/news/press_releases/2018/oxytetracycline-12-10-2018.php

Is the reason you're studying virus-delivered antibiotics related to the concerns over broader antibiotics use resulting in bacterial resistance issues in humans? Or is there another reason for it?

Comment by I_AMA_giant_squid at 10/03/2025 at 17:32 UTC

4 upvotes, 1 direct replies

Are there actions that everyday people can take to help prevent the spread of these citrus (and other ) plant viruses?

Comment by ArrowsOfFate at 10/03/2025 at 19:17 UTC*

4 upvotes, 1 direct replies

Why did your lab focus on making an antibiotic virus to already sick trees, rather than targeting the psyllids with something like neutered males as is done with the screwworm in Central America? It doesn’t seem like an antibiotic virus would be a permanent solution but one that needs repeated forever as the pysllids will inevitably evolve to fight your virus off and are even quite likely to become stronger and do even more damage from the evolution..

Seems like it would be a losing game to try to immunize millions of hectares of trees and wouldn’t that need to be done tree by tree, thus making the cost insanely high and impractical for mostly poorer farmers, let alone natural citrus.

With the screwworms they are airdropped to create a defensive perimeter so they can’t advance back into America. I imagine it would still be expensive to clear all of South America though, seeing as it hasn’t been done.

Comment by ConfidentFlorida at 11/03/2025 at 11:37 UTC

3 upvotes, 1 direct replies

There are abandoned orange groves all over Florida and when I drive through them there appear to be a fair amount of trees with healthy looking oranges.

Why can’t we study the trees that are doing well and see what kind of resistance they have?

Comment by _Guron_ at 10/03/2025 at 17:59 UTC

2 upvotes, 1 direct replies

So you combat bacteria using viruses, how interesting! What these viruses does to the plant? Does it harm it?

Comment by onionsaredumb at 11/03/2025 at 02:59 UTC

2 upvotes, 0 direct replies

No questions, but thanks for sharing. I went down a bit of a rabbit hole in Wikipedia regarding plant viruses as a result, haha.

Comment by Level9TraumaCenter at 10/03/2025 at 16:42 UTC

2 upvotes, 1 direct replies

Are there any data showing which, if any, consumer products with nicotine such as vapes contain viable particles of tobacco mosaic virus?

Comment by Dasheek at 10/03/2025 at 19:15 UTC

1 upvotes, 1 direct replies

have developed an approach to combat this disease by infecting trees with a virus that delivers antibiotic agents to the location where the bacteria live

So it is like with covid vaccine? Employ existing tree cells with custom virus to produce antibiotic agent? Or is it tailored bacteriophage?

Comment by Komaitho at 10/03/2025 at 21:27 UTC

1 upvotes, 1 direct replies

Is it possible to develop viruses that adapt to antibiotic resistance in the pathogenic bacteria while in the host? Or is something along the lines of a decision tree of different antibiotics more feasible that get activated when another one fails? Is antibiotic resistance in plant pathogens even a big concern?

Comment by StabithaStevens at 10/03/2025 at 22:20 UTC

1 upvotes, 1 direct replies

How easy is it to infect massive numbers of trees with a plant virus? How many viruses are most citrus plants already infected with generally? Will Silvec Biologics have to devise a new vector for different geographic areas? Will there have to be a new antibacterial viral vector every season??

Comment by HeWhoisNosy at 11/03/2025 at 02:18 UTC

1 upvotes, 1 direct replies

Is selective breeding of citrus a main reason why they are so vulnerable to disease?

Comment by goldtrainkappa at 11/03/2025 at 10:40 UTC

1 upvotes, 1 direct replies

What genetic pipelines do you use in your work and do you work with microbial communities as part of your work? As in addressing the wider microbiome

Comment by ThinNeighborhood2276 at 11/03/2025 at 13:33 UTC

1 upvotes, 1 direct replies

How effective is the virus-based approach in field trials, and are there any potential risks to non-target plants or the environment?

Comment by Yaver_Mbizi at 11/03/2025 at 16:45 UTC

1 upvotes, 1 direct replies

If the worst comes to pass, would it be possible to just switch our citrus cultivars like happened with Gros Michel -> Cavendish for bananas?

Comment by vaynefox at 12/03/2025 at 14:35 UTC

1 upvotes, 1 direct replies

So far, what are the viral pathways you observed in your research, and how does it affect the speed in which the virus infects a plant cell?