Root rot and Phosacid

[GavinG]

I have had root rot problems when old Japanese maples are put into bonsai pots - larger containers for growing on are no problem. I've had some success with preventative applications of Fongarid in winter and summer (root soaks) but Fongarid is now not available.

The replacement Phosacid is a foliar spray, and instructions suggest not to spray when trees are dormant, or in extreme heat. Have other growers used this product preventatively, and and if so, how and when?

I also have root rot problems with Banksias and Grevilleas - those who grow them successfully often have them on wire mesh shelves with good air circulation. I'm thinking of trying out Phosacid on these species as well. Any thoughts?


Gavin

[Pearcy001]

What sort of mix are you using Gavin?

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[treeman]

Phosphorus acid works ok on phytophthora but not on pythium so it's hit or miss. More importantly you need to discover why the rot is happening in the first place. With maples, you should wash the roots clear of any old soil and replant in a mix with particles no smaller than 3mm. Also use an aeration layer of 5 or 6mm particles and use a pot just big enough to allow about 5cm of room for the roots. You should not have any further problems.
With the banskias do the same but don't wash the roots. The wire mesh won't make much difference. Good luck.....

[Grant Bowie]

Hi Gavin,

I found Fongarid drench very useful for stopping rot in Banksia etc and allowing the tree to recover and thrive. Retail wise it is going to be hard to replace.

I have used Phosacid in the past(many years ago) as a preventative spray but can't really say if it is effective or not on trees that are already suffering with rot.

Timing of repotting Banksia (during warmer weather) is critical as well as potting mix. A root bound tree doesn't tend to get root rot so don't repot too often and don't repot in or going into cooler months.

Japanese Maples are usually safe to grow in Canberra but old Japanese Maples lose vigour and small pots don't help. I have seen a number of old Japanese maple that are just not worth persevering with (here and in Japan) as they just won't bud back etc.

Grant

[treeman]

old Japanese Maples lose vigour and small pots don't help.

Grant

Only if they are not grown correctly.

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[bodhidharma]

Japanese Maples are usually safe to grow in Canberra but old Japanese Maples lose vigour and small pots don't help. I have seen a number of old Japanese maple that are just not worth persevering with (here and in Japan) as they just won't bud back etc.

Grant

Hi Grant,
Can you define "Old" for me please. We all have different concepts of old, in Japan a 300 year old tree is classified as old but in Aus it would be 50 years?

[Grant Bowie]

Japanese Maples are usually safe to grow in Canberra but old Japanese Maples lose vigour and small pots don't help. I have seen a number of old Japanese maple that are just not worth persevering with (here and in Japan) as they just won't bud back etc.

Grant

Hi Grant,
Can you define "Old" for me please. We all have different concepts of old, in Japan a 300 year old tree is classified as old but in Aus it would be 50 years?

Old is a flexible concept. Japanese maples are mountain trees and would live a slow, long natural life of whatever timespan in their natural climate. Grow them nearer the coast and they grow quicker and exhaust quicker and die/senesce or fail to proceed in a shorter period.

I can't quote for maples precise years but for the Lebanese Cedar I have heard something like 1,000 years in their native climate, about 400 years in England and about 150 to 200 years in Sydney.

A lot of japanese maples are poorly grown initially unfortunately and it is is hard to correct later. Treemans maple looks like an example of a very well grown tree over a long period.

Grant

[GavinG]

Pearcy: My usual mix is 50/50 native potting mix and coarse grit (pumice or diatomite). I have potted maples in 80/20 pumice/coco peat, and even 100% pumice, and still lost them mix seems to make little difference with this problem.

Mike: what works with pythium rot? Any search I've done just comes up with seed treatments for crops.

Grant: I've never managed to save a tree once the symptoms appear, with anything, but preventative dosing seems to work for me.

Bodhi: "Old" always means older than you or me. We're not old. Yeah right.

Thanks for your input gentlemen.

Gavin