Friday, May 13, 2011

Canna virus in Malaysia

Cannas in Malaysia are susceptible to what looks like a viral disease. The symptoms in Malaysia are stunting of plants, patches of dead tissue on young leaves, reduction of flower-size to half the normal size, and progressive stunting and weakening of the clump or bed until no more shoots appear. Separating out the rhizomes and cleaning them before transplanting does not help unless the disease is detected before it has spread to all the rhizomes.

At the early stage of infection, the bed should be dug out and the pieces of rhizome bearing swollen buds separated out for replanting. When new shoots emerge, the plants that are infected can be recognized by dead patches of tissue on their leaves. Such plants should be eliminated immediately, leaving healthy plants for starting new colonies. The virus takes several weeks to spread through a bed of cannas so there is time for such corrective action if one is alert to the symptoms of infection.

The virus does not travel in the air or soil. Plants in the next bed a short distance away may remain free of infection. I think the best way to prevent infection is to remove all canna shoots as soon as they have finished flowering. Such spent shoots should be cut off at their base. A regular once-a-week pruning programme will improve ventilation of the canna bed and deter white flies from settling on the leaves. White flies suck sap and are probably the agents spreading the virus in Malaysia.

In temperate countries, where cannas are sold as rhizomes, the canna virus has been disastrous for the canna trade because it is impossible to tell whether a rhizome is infected until it is grown out. In Malaysia and elsewhere in SE Asia, cannas are sold as full-grown plants, usually flowering, so it is immediately apparent from the condition of the plant whether it is infected.


DAR said...

Dr, I need to communicate with you regarding a project. Can I have your email. Thanks..

Architecture Fun said...

Hi, Dr,
Thanks to you and the help from Nirzam, I had managed to get the avocado plant and also the copy of your autographed book.

I had planted the tree in my garden and hopefully it will grow well.

Jeanne said...

Dear Dr Ng
So fasinated with your work and interest.
Do you have a workshop of sorts... that one can attend??

Am building our own home with garden both on the ground and on concrete roof.
Needs lots of education on prep work etc to make sure the garden works and ready to take the trees and plants.
Would really love to talk to you if at all possible

Dr Francis Ng said...

Jeanne, you will surely have a lot of fun starting your new garden. If you have any specific questions you can pose it in this blog and I will try to respond. It may also attract responses from other readers.