How to Identify Dahlia Viruses and Prevent Virus Infection from Destroying Your Plants

Dahlias provide a welcome splash of colour in your allotment or garden border, but frustratingly they can become infected with a number of different plant viruses.
You can tell if your dahlia has a virus infection by looking at the symptoms on your dahlia plant. Dahlias which are infected with a virus often have yellow leaf veins or yellow mosaic, mottled, or circular markings on their leaves. Infected dahlias have distorted or twisted leaves, and the dahlia plants have stunted or poor growth. In this video I show you what dahlia virus infection looks like and I explain how to diagnose virus infection on your dahlias.
Symptoms of dahlia viruses can be confused with other common dahlia problems such as nutrient deficiency and insect feeding damage from leafhoppers and thrips. I show you how to distinguish dahlia virus infection from nutrient deficiency and insect feeding damage on the leaves.
I show you three different methods you can use to prevent dahlia viruses from spreading and killing your plants. By following these simple treatment strategies you can keep your dahlia plants healthy!
If you want to identify exactly which virus is infecting your dahlia then you can buy test kits, but the control methods which I describe remain useful, no matter which virus your dahlia plant has. The most common dahlia viruses in the UK are Tobacco Streak Virus, Tomato Spotted Wilt Virus, Impatiens Necrotic Spot Virus, Cucumber Mosaic Virus.
⏱️Timestamps
00:31 Dahlia leaf colour - virus symptoms
01:15 Dahlia leaf shape - virus symptoms
02:09 Dahlia plant growth - virus symptoms
02:30 Virus infection vs Nutrient deficiency
03:06 Virus infection vs Insect damage
03:32 Common dahlia viruses and should you test for infection?
04:07 Remove virus infected Dahlias
05:30 How to prevent spread of Dahlia viruses
07:29 You now know about Dahlia viruses!
🔬 Science links:
1️⃣ Presentation of commonly seen viruses in dahlias in the US, Hanu R. Pappu (PDF): dahlia.org/wp-...
2️⃣Uneven distribution of dahlia virus in the plant makes careful sampling important for accurate use of test kits. Asano S, Hirayama Y, Matsushita Y. Distribution of Tomato spotted wilt virus in dahlia plants. Lett Appl Microbiol. 2017 Apr;64(4):297-303. doi: 10.1111/lam.12720. PMID: 28129432. academic.oup.c...
3️⃣Dahlia virus testing: www.agdia.com/...
🎵Music attribution:
"Divertissement - Pizzicato (from the ballet Sylvia)" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
creativecommons...
"Brandenburg Concerto No. 4 in G, Movement I (Allegro), BWV 1049" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
creativecommons...

[@rebekahtheukplantdoctor]

Do you have trouble knowing whether your Dahlias have a virus infection, or another problem such as nutrient deficiency? Hopefully this video helps! 🌸

[@richellerudinski2004]

Well it helped. But now I think I have several dahlias with virus. So bummed. Guess I should find a horticulturist.

[@richellerudinski2004]

Still you didn’t answer my question. Do ALL dahlias have the same leaves? No mater the variety.

[@rebekahtheukplantdoctor]

​@@richellerudinski2004 This may answer your question: Most of the garden dahlias we grow are the same species - the common garden Dahlia, or in Latin, the Dahlia pinnata. The colour of the leaf can vary from bright green to dark red, but yes, Dahlia pinnata leaf shape remains broadly the same across this species. Other dahlia species, like the imperial tree dahlia (Dahlia imperialis), have slightly different leaves. Dahlia imperialis has much larger, more divided leaves compared to the common garden dahlia. 🌸

[@richellerudinski2004]

Thank you for your video. I’ve got a question. ALL Dahlia leaves are the same? All varieties.

[@rebekahtheukplantdoctor]

Good question. Virus symptoms will vary slightly depending on the cultivar and depending on the virus causing the infection. Dark leaved dahlias for example may show different leaf colouration. However, if you see distorted leaves, different colours on the leaves (often yellow and sometimes ring shapes), and stunted growth of the plant, then virus is the likely cause. 🌸

[@Mindy-s-channel]

I grew mine from seed, and I think a few of them have this virus. Was the seed infected? Or did they become infected after germination?

[@rebekahtheukplantdoctor]

Good question! A few of the common dahlia viruses can be transmitted via seed. So infected seed is certainly a possibility, particularly if you saw symptoms in very young plants. However, the plants are loved by aphids and other insects which can transmit viruses, so they may also have become infected as seedlings. 🌸

[@Mindy-s-channel]

If my dahlias do have this virus, could it possibly infect my roses or hydrangeas? Or possibly salvia or garden Flox? Or possibly daylilies?

[@rebekahtheukplantdoctor]

Dahlias unfortunately get a few different viruses. The dahlia mosaic virus is specific to dahlias, so will not infect other flowers in your garden. But some other dahlia viruses are more general, such as cucumber mosaic virus (which despite its name will infect hundreds of other plants including lily and phlox). This means it’s always wise to remove symptomatic dahlias quickly to reduce the chance of the virus spreading. 🌸

[@Emgee78]

I think I have diseased dahlias, but since they're in their own individual containers and not a threat to my other flowers, I'm going to keep them for now and see how the flowers turn out in all their mutant glory.

[@rebekahtheukplantdoctor]

That sounds like a good balance of caution and experimentation, Emgee! There are so many different viruses and diseases, if we threw out every infected plant we wouldn’t have any flowers left! Just remember that insects and tools can spread diseases between plants, so if you do have other healthy dahlias keep them at a distance and clean your tools. Good luck with your dahlias 🌸

[@Emgee78]

​@rebekahtheukplantdoctor Thank you. The dahlia plant is already hip-tall and has buds, and I'm excited to see the color despite how questionable some of the leaves look.

[@catie8604]

Despite being in individual containers, diseases can still spread to other plants.

[@joliecastro6768]

My delhia has a dust like substance in it leaves does it mean it has a virus?

[@rebekahtheukplantdoctor]

Hi Jolie, if the powdery substance is white, then it's most likely powdery mildew fungus. Powdery mildew fungus is quite common on dahlias and they are often able to tolerate it and carry on growing, so no need to remove the plants. You can help the infected plants cutting out the worst of the infected branches, by spacing the plants a bit more widely and allowing more airflow through the plants, and watering at the base rather than overhead. If you want to use a fungicide then its best to check what's available in a garden centre near you. I hope this helps, 🌸

[@muhammedsalimmsl4322]

👌

[@organicgardenmamavictoriab2768]

Oh no my Dahlias have a viral infection because they are short

[@rebekahtheukplantdoctor]

@@organicgardenmamavictoriab2768 There are lots of other reason dahlias can be small, lack of nutrients, drought, shade, or they may have been eaten by slugs or snails! My dahlias this year are also small because the slugs keep eating their growing tips. Virus infection will usually also have the other symptoms of yellow marks on the leaves and leaf distortion alongside the short growth. Happy gardening 🌸