****June 2013 Edit – Important Information****
The cause of the rot shown here is not fungus. After a long process of elimination, some plant pathologist colleagues determined the cause is most likely fertiliser burn. While fertilisers (I used slow release fertiliser here) are useful for getting seedlings up to size, overdoing the dosage can induce symptoms similar to a plant affected by rhizome rotting fungi – wilting pitchers, dead rhizome tissue and death shortly afterwards. These symptoms are caused by the roots being burned by the fertiliser and reducing water flow through the plant. In plants infected with fungi, the infection kills the tissues transporting water through the plant, producing much the same outcome.
For reference – this case involved a mature Sarracenia flava var. cuprea in a 140 mm pot. I had fertilised it with around 12 pellets of slow release fertiliser the previous spring.
The recommended dose of slow release is 4 pellets or less per 100 mm/4” pot.
Aside from the different cause, the information below is correct for the symptoms, and applies equally to fungal rots and, obviously, fertiliser burn.
****Amended original post****
I had a very nasty surprise last week – several of my best Sarracenia flava clones started wilting, even though they were sitting in trays of water. I have seen this before in Sarracenia that have not been divided often enough. You should dread this type of symptom, because it means you are on the verge of losing your plant and must act immediately.
You will need the following:
- Garden hose with a trigger spray (preferably with a gentle rose-type spray)
- Sharp knife
- >5% bleach solution (you don’t need to be precise – a good splash of bleach topped up with water. I like to have this in an old detergent squirt bottle for ease of application.)
- Disposable gloves
- Broad-spectrum, systemic fungicide and pesticide (I use Yate's Rose Gun concentrate. See http://www.yates.com.au/products/disease-control/ready-to-use/yates-rose-gun-ready-to-use/ for the active ingredients. This link is for the ready-to-use, as I can’t find a web listing for the concentrate – its the same actives, though. Always follow label directions).
- New pot and potting media
The first step in dealing with this is to immediately de-pot the plant. Wearing gloves, wash off as much of the soil media as possible with the hose and sprayer. Here is one of my plants after being depotted. I have split it into two to show the infected area. Note the wilted pitchers.
Once the plant is depotted, examine the rhizome for dead growth. Start at the end furtherst away from the growth point and gently flex it. The rotten, dead portions should break away easily. Here is a close-up of what rotten rhizome looks like.
This infection is a fungal one – bacterial infections tend to be more slimy. Using the knife, you need to chop off as much of the dead rhizome as possible, being careful to preserve as many roots as possible. But make sure you remove every sign of dead rhizome. In between cuts, wash off your hands with the hose, then squirt on some bleach and rub hands together to sterilise (important if you are dealing with fertiliser burn too – pathogenic fungi love damaged and stressed tissues and are likely to infect them). Also sterilise the knife in this way. Infecting good tissue will only cause new problems.
This is where you need to be careful, as it is just so easy to miss
diseased dead tissue. The photo above may look like clean rhizome, but it is not. There is still a layer of fungus infected tissue around the top. This needs to be carefully removed. Also, Sarrcenia rhizome turns brown on exposure to the air – the brown ring in the middle of the rhizome and the spots around it are perfectly normal.
Sarracenia trivia # 1: the dark tissues in this photo show the division of this plant’s vascular tissues. The outer layer is water-transporting xylem, while the inner layer is the nutrient-transporting phloem. These tissues run lengthways down the rhizome and are arranged in bundles – think of them as water pipes or fibre-optic bundles. The dark spots mark dense areas of cells at the centre of each xylem bundles.
If you are lucky, there will be enough intact tissue and roots left to save your plant. But sometimes it comes right down to the proverbial knife-edge. This photo shows one piece of rhizome where the difference between dead and live tissue is very slight indeed:
I was very lucky – the root at left allowed me to save this division. Always try to save as many pieces of rhizome as possible – you’ll be surprised at how little tissue (and how few roots!) you need to be successful. And sometimes that little, insignificant looking piece of rhizome may just save that really special plant from oblivion…
But sometimes, there is no chance whatsoever. This plant was rotted right up to the growing tip…
As was this plant. This is why recognising and responding to rhizome rot quickly is important – a few days earlier and this piece may have be salvageable.
Before repotting any rot-affected plants, be sure to spray the divisions - before potting - thoroughly with the fungicide-pesticide, and again as per label directions until the plant is back up to strength. Some growers suggest soaking the plant in the solution, but it usually goes against label directions to do this. Remember, label directions are your protection. Using a chemical in any other way leaves you entirely liable for any damage it causes (including to your health!). This also applies to fertiliser burned plants!
See also my suggestions for emergency repotting for how to get your plant back into action.
Merry Christmas, Happy New Year and Good Growing.