root rot- identification, control and iradication

[Jamie]

hey people,

while we continue through our progression of pests a disease we come across a very common problem many beginners have, root rot, it is generally cause by overwatering and having the soil to moist all the time which allows fungi to grow, yes root rot is a form of fungi, not just because the roots are constantly kept to moist. there are heaps of different forms of root rot fungi so instead of covering all of them i will give a basic rundown as it is mostly treated the same way.
other causes are poor drainage (which in turns keeps the soil to moist and cool allowing for fungi growth), inadequate light and overcrowding all make perfect conditions for fungi to grow.


root rot fungi first enters the tree via the small fine feeder roots, if the conditions are kept constant in that the fungi can thrive it will generally take over the whole root system in 7-10 days, causing death of the tree/plant. infected roots will become brown and mushy due to the excessive tissue decay and the wet environment, where as healthy roots are an off white colour and firm. infected roots will no longer function properly with the passage of water and nutrients to the tree, this shortage of nutrients and poor intake will effect the plant/tree by signs of yellowing leaves, poor or unhealthy looking growth, deformed growth, wilting, premature leaf drop. these general symptos can also be accompanied by others but these are the main ones, you will also notice that the symptoms will go from the base up.

a couple of pictures of root rot below. (these are just two pictures of two different forms of rot, there are many others)

root rot.jpg

rootrot1.jpg

control

so how do we control such problems like root rot and fungi, the best way to stop it is to not allow it to begin in the first place, now being a beginner in this fine art of ours this is obviously a common problem as they generally overwater in fear of not watering enough, good watering practices is a good lesson to learn straight away, if you avoid overwatering and allow sufficent time for the soil medium to "dry" out (which is just moist as we dont want them to dry out completely for to long either as that can be hazardous aswell).

if you do have a root rot problem what is the best way to stop it, first it has to be identified as root rot quickly, the quicker the better, it can call for out of season repotting but if not attended to could be the difference between a dead tree or a live one.
once the tree is out of the pot inspect the roots and soil, it will probably be quite moist and most likely very poor drainage.
any roots found to be infected are to be pruned off and destroyed, not chucked into a compost bin as this could spread the fungi.
once all infected roots are pruned it is vital to repot into a free draining soil/potting medium, if using an organic medium add some sharp sand, grit or similar to allow it to be free draining, if using an inorganic medium you most likely will have a very free draining medium anyways, i like using diatomite as a base for my mix with a small amount of organics.
lastly remove any effected foliage as this will just waste energy the tree needs to recover.

if this process has been done out of season then after care is crucial, keep in a shady spot until new growth appears and it starts picking up again.
keeping an eye on the tree is vital in the coming weeks after the procedures as the tree will be quite stressed after the ordeal. keep a very close eye out for any other problems especially insects and bugs, a stressed tree will be more prone to pest attacks, they seem to know a tree is stressed.
the only other thing to do would be to give it a dose of seasol and superthrive or similar, this will help perk the tree up a bit and hopefully bring it back on track.

if anyone has anything to add to this thread please feel free, if we can build up a section of help threads it will make it a lot easier for the beginners and experienced alike to jump straight to it.
personal experiences, thoughts or discussions welcome, same with all the other threads i have posted on pests and diseases.

jamie

pictures sourced from various sites.

[Ron]

Timely article for me, Jamie, not because I've noticed any root rot but because it's rained, often quite heavily, here for the past three weeks. On the 3 or 4 days of sun recently it was maximum humidity (and the lawn grew about 6 inches in a day!) and now yesterday it rained heavily again. So the pots have probably had very little chance to "dry" out. I have been worried about the negative effects of too much rain.

Also with the first potted bonsais I bought (mid January this year), the seller repotted one of them as a demo for me when I picked them up and used the cheapest generic brand of potting mix without anything added. As I've learned a bit more about bonsai this has caused me some worry. I didn't want to repot it so soon after buying it for fear of killing it (a small-leafed Syzygium).

[Jamie]

gday ron,

what i would be doing if you have had heavy rains for so long and you are worried about problems arising from this bring the trees under shelter for a few days until the rain ceases, it shouldnt be a major problem as it will atleast give the trees some drying time instead of being drenched constantly.
repotting now after it has only just been repotted could possibly cause problems but in my mind the with the right after care it shouldnt be a major issue, if you can do it without disturbing the roots to much even better, i cant see that happening though if you are adding a grit medium to the soil. i highly recommend the use of diatomite with some organic matter mixed in, a standard store bought bonsai soil will do, this mic is incredibly free drain but will hold moisture and nutrients at he same time, there are others that will swear by straight diatomite as well, it is great stuff, and it can be washed and reused.

so i would just bring the trees under cover until the rain finishes up and if you get a break where it is sunny for a day or two take them out and if it starts raining heavy again bring them in, i do this myself if it is torrential rains that dont stop for weeks which we can get up here.
i do leave my growing on stock out in the conditions though and they havent had any problems.


jamie

[Ron]

Thanks, Jamie.

During the first few days of rain I actually made sure they all got plenty of that rain believing it's beneficial to them after using hose water (chlorine, fluoride etc). I think this is good practice?

Any more rain and I'll move them in under the eaves where they'll get very little of the rain.

Ron ...

[Jamie]

yes ron, the rain is excellent for them, if you can use rain water at all i would recommend that, i have a ten thousand litre tank and thats all i use for my trees, and they are a lot happier then when i was at my old place just getting tap water. the rain is good as though because it helps to unlock nutrients that the plant can then take up.
and as you have said about the chlorines and all the other chemicals put in tap water, i dont like it and that is why i use my tank water thats collected rain water.


jamie

[craigw60]

Hi Jamie,
You are so right on the issue of over watering. The best advice I have ever had on this issue came from Shinichi Nakajima who told me keep your trees dry, By that he meant do not keep your trees constantly wet. It is so important to allow the plants to dry out between watering and allow the spaces in the potting mix to fill with air so the roots can breathe.
Craig

[Jamie]

spot on craig, it is also a matter of oxygen transfer when we water as we water to fill the pot and then some as to push old air out and replace with fresh, it is always a good idea to allow the trees to have a breathing space of not being to dry but moist as such without drenching. i think proper watering can be one of the hardest things to learn as it is always different for everyone, it even changes depending on where you are if you move, i moved a couple of years ago and the watering regime here is completly different to the what it was at my old house. it comes down to peoples micro climates and it is something we all have to learn for ourselves and learn what our trees need. as one trees requirements may call for more water than the tree next to it, thats why i dont like auto watering systems either, if we spend the times with our trees watering them and checking over them while doing so then half the battle is won right there because if you check your trees while you are watering it covers any look out for pest or disease aswell and also other things like wiring biting in for instance.


jamie

[Glenda]

One of the biggest things I had to learn when I started Bonsai is to water ENOUGH. I had never had great success with any plants living long - and I think it was because I underwatered them. When I first started I read everything on the Bonsai4me site, and a few others, which said water until the water runs out the bottom, give it 10 minutes or so, then water again. In hot weather, plants may need two or more waterings every day. This is when I switched to diatomite, as these sites also said it was virtually impossible to overwater when using kitty litter or diatomite.

I went to Tasmania for 11 days over Christmas. I left an automatic sprinkler system on during that time, and (you guessed it) we had torrential rain at home the whole time I was away. Came home expecting my plants to be keeling over with root rot, but not one single plant suffered because the diatomite is free-draining. Not all my plants are in diatomite, however, but most of them had been repotted recently, and none of them suffered either. We have had almost constant rain since, and none are unhappy.

While I hear what you are saying Jamie, I guess I am just saying we need balance, and perhaps the problem of root rot is more about the soil being free-draining rather than about overwatering.

Glenda

[Ron]

One of the first I read about in bonsai was the use of diatomite. Google AU came up with Maidenwell brand which only seems to be available in Qld.

I asked my three local general nurseries about Maidenwell and they had not heard of the brand. Then again they also said they'd never heard of diatomite!

[Glenda]

One of the first I read about in bonsai was the use of diatomite. Google AU came up with Maidenwell brand which only seems to be available in Qld.

I asked my three local general nurseries about Maidenwell and they had not heard of the brand. Then again they also said they'd never heard of diatomite!

I have had the same problem, Ron. I eventually managed to get some "Septone Dry-up" - an industrial chemical-spill cleanup agent. It is diatomite, but also has a lot of clay mixed in which has to be washed out. I get it from a local hydroponics supplier which is very small, part-time, home-based business. Perhaps some of the chemical suppliers may have it? It isn't the quality of Maidenwell, but it suffices. Have been trying to talk the local Bonsai club into getting an order from Maidenwell between us, but most of them have been bonsaing for years, are rather set in their ways and the thought of inorganic soils makes them shudder.

There is another brand of diatomite mined in NSW, too.

Glenda

[Glenda]

Mt Sylvia Diatomite is mined in Gatton. It is sold under the brand Purasil.
Glenda

[Grant Bowie]

It is raining solidly in Canberra today and for the last two days. Yeah, my tanks are full again.

If you are worried about root problems and you can't move trees under cover I remember reading a book from Taiwan where they put a chock under one side of the pot to help drainage during the wet season.

Grant