Being in a tropical country, we are blessed to have our garden watered naturally by the occasional and seasonal rainfall. But this sometimes poses a problem to roses when they are left too long or too often under the wet weather condition.
Sometimes you will see the canes or branches of your roses turned black and rot, and within days the infection turns serious and moves downward. If it is not treated properly, it can severely infect the entire plant and soon your rose will die.
What is that black and moldy thing on the cane?
It’s called rose canker or stem canker. It happens when fungi enter the plant tissue through open wounds. It usually happens within few days after you deadhead (potong bunga tua) or prune (pemangkasan batang) your roses. Sometimes it happens for no reason at all due to open wounds on the bark or stems that you know nothing about. It also can happen to old established canes that have lost their vigor.
When this most likely to happen?
It most likely to happen during rainy season, the fungi love wet condition, because that’s when they can germinate and spread. It also happens when your roses are too wet for too long, under stress, sick or defoliated.
The fungi are not high level pathogens so they won't spread when conditions are favorable for plant growth.
What to do with roses with canker?
For canes that are already infected with canker, just cut the canes down to a healthy level and place the sealant on the wound.
If canker is affecting one of your main stems, rest assured that the other main stems will not be affected once the infected cane is treated. Keep the tree healthy, well watered and fed however. But, if your rose has only one main cane and it’s infected, my advice is to without delay, save some cuttings for propagation. That tree and that rose you like, will be gone in few short days.
How to avoid rose canker?
- Don’t let your roses stay wet for too long. Place your rose where it can have enough sunshine. The sun will ensure the plant is dry.
- Make it a habit to put sealant after making any big wounds on the trees.
- It helps by keeping your pruners clean; which can be done by dipping it into a bleach solution before use.
- Make sure your deadheading routine is done correctly.
- You may want to spray fungicide to kill off the fungi spores and protect the rest of the tree.
- Importantly (and I know many people make this mistake!) is to keep the tree well foliated! That means keeping the leaves on the tree and not off the tree. A lot of people resorted to ‘togel’ling (defoliate) the tree whenever it has troubles, for whatever troubles there might be. I can tell you it is so wrong! It’s like stripping off your skin whenever you catch a cold.
So, treat that canker and best of luck to you and your roses!