Aroids (the family Araceae)

[Maggi Young]

Disturbing news about the loss of the Utrecht Arisaema candidissimum , Pascal.

Janis is away in Turkey at the moment, so do not be dismayed by  his lack of reply meantime!

[Pascal B]

Maggi,

Virus in Arisaema is a major but yet little known threat to collections, the most common infections are of mosaic virus and poty virus. Some growers mistake these infections with nutrient difficiency but it seems most present in sections Sinarisaema (ciliatum, consanguineum, concinnum, erubescens) and Franchetiana (franchetianum/fargesii, lichiangense and candidissimum). Common vectors for the spread of these virus are of course aphids but also those little leafhoppers (Hauptidia maroccana) that seem to be on the increase lately. Scale insects and mealybugs seem less of a threat. I try to keep my collection virus free but the tests to check for virus infections are quite expensive. I am pretty confident I have no virus in my collection but I know with well over 2000 Arisaema tubers that is a bold statement....

The worrying sign seems to be that propagation by seed is no guarantee the offspring will be virus free so education is key. Good pictures to illustrate virus infection can be found here:

http://botgard.bio.uu.nl/temperate/?gal=default&genus=Arisaema%20virus&all=#current

All pictures are from species of section Franchetiana but the signs for the other sections are similar. It should be noted that virus infection is visible from the moment the leaf unfurls, lighter spots that appear later in the season are generally not virus caused.

Pascal

[ArneM]

Nicole, I will try that tomorrow.

Thanks for correcting me, Pascal.

[Ezeiza]

Pascal, thanks for the great info. You say virus can be transmitted in Arisaema seed?

[Pascal B]

Yes, it seems some types of viruses are also transmitted through seeds, something that was also remarked by A J Halstead, Principal Entomologist of the RHS in a personal communication to me. It is certainly not my intention to make everyone paranoid now but just like with every other plantdisease we simply need to keep an eye on it and be aware it exists. Arum and Dracunculus can also be infected with viruses but because Arisaema are getting increasingly popular, with that popularity also comes the risk of spread. But it is not confined to cultivated plants, during a trip to Nepal I have seen hundreds of infected Arisaema erubescens and in West Bengal I even saw a few infected Arisaema galeatum.
Underneath a picture of an infected erubescens. To be honest, it does look quite attractive but ultimately the plant will weaken and die. As I have not been able to take a fresh leaf sample I can not tell which virus this type of leaves causes.

[Ezeiza]

Viruses in Iridaceae are transmitted through seed but have no idea of this in aroids as well. We have several species from Utrecht seed so this is distressing news.

Those you saw in Nepal, were near tobacco or taro/dasheen fields?

These virused plants images are invaluable.

Leafhoppers are a problem here too and transmit viruses very rapidly from weeds to garden plants. The attack salvias first.

[Pascal B]

Those you saw in Nepal, were near tobacco or taro/dasheen fields?

I can understand what you are aiming at for the symptoms but no, it was in the middle of nowhere with no crop fields in a 5 km range. Taro is cultivated at much lower elevations and they don't grow tobacco in Nepal as far as I know. There is something else they grow that you can smoke in tobacco but that is another story...
Dasheen mosaic virus generally causes lighter leaf areas, particularly in Colocasia (Taro) but tobacco mosaic virus or a related virus could be a possibility.

[Ezeiza]

The only wild plant we ever saw infected with virus was Talinum paniculatum but in the area people had squash sown everywhere. With a machete it is very easy to infect wild species while "weeding". This scenario is what I had imagined for Nepal.

[Lesley Cox]

You can pour a spoonful of water into the flower to stop the bad smell  and keep your plant indoors 

Really? Does that work?

[WimB]

You can see one of my pictures in that link Pascal gave. That A. candidissimum was diagnosed with Dasheen mosaic potyvirus. The plant itself did not seem to suffer from the virus. I had seen that pattern in the leaves since I bought the plant (one corm) and it took 10 years before someone pointed out it might be a virus. In the mean time the plant had multiplied to more then 50 corms which were all flowering.
The seedlings had the virus too.

[K-D Keller]

Two aroids with no bad smell are in flower now 

I have got another question:

Biarum marmarisense is a spring or an autumn flowering species? It flowers after the leaves, before the leaves are growing or with the leaves? Regular dormancy is in summer or winter? 
My plant is growing very well in winter but there is no flower. 

K-D

[Johan Nilson]

Pascal,

Thanks for all the valuable information concerning virus given here. Sadly I am now suspecting that maybe some of my own plants are infected. I guess that the only thing to do is to get rid of them?  

I noticed that my A. fargesii had this lighter pattern on its leaf and I am guessing now that it most be this virus. Besides that species I am now suspecting that a friends bulbs of Arisaema consanguineum may be infected.
He has been growing a great number of this species in pots end in fishboxes for a couple of years. The last two years a lot of them have died back, but without having any obvious lighter patterns on their leaves. Earlier years the bulbs has always been perfectly good looking, but at time for repoting last year I noticed that a lot of the bulbs had strange looking cracks in them. Sorry, but I don't have any pictures of this to share but maybe you are aware of what I am talking about.
Have you come across this before and if so, do you thing this could be caused by this virus?

I saw a specimen of Arisaema galeatum growing wild in the West Bengal which I think look suspicious?



Picture 1 - Arisaema galeatum
Picture 2 - Arisaema fargesii

Johan

[Johan Nilson]

Some Aroids from the greenhouses at Gothenburg Botanical garden. All very fascinating!
The first Arisaema to flower this year, Arisaema fimbriatum (pic 1 &2) and Arisaema taiwanense (pic 3).
Dracontium sp (pic 4)
Helicodiceros_muscivorus (pic 5,6,7)

[Johan Nilson]

Some more..

Amorphophallus paeoniifolius, Amorphophallus variabilis & Amorphophallus levallei.

all a bit smelly but still fantastic creations!!

[Johan Nilson]

guess I uploaded wrong pic.

Here's the second picture of A. paeoniifolius