Anthracnose Avocado (forum)

Araich starts with ...
I'm almost certain that my 1 yr old Hass avocado has an anthracnose fungus attacking the leaves. Anyway, I have a copper spray but notice that the droplets just sheet off the leaves, and this seems ineffective.

Does anyone add a detergent or other to break the surface tension? What is safe to use.

This fungal attack is a result of rain + heat + shade-cloth enclosure and the reduced airflow resulting from a giant tomato plant along one side of the enclosure. It began with a yellowing between the veins of the leaves and progressed to curling, tip browning and dead brown spots between the veins. Diagnosis was by exact match with this description http://www.ipm.ucdavis.edu/PMG/r8100711.html#SYMPTOMS

Time: 25th December 2009 11:33am

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About the Author Araich
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Wayne says...
You certainly need a wetting agent Araich, 60mls to 5L water approximately, Agral is a good one. I use an unscented liquid pure soap, most detergents do more harm than good so be carefull there. Lux flakes are also a pretty good wetting agent but I always have trouble dissolving them.

Good luck and Merry Christmas to you

Time: 25th December 2009 5:09pm

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Araich says...
Thanks Wayne, I tried a ph balanced hand soap and it seemed to work great. A bit hard to tell however as the avocado is now throwing all it's leaves, down to 4 or 5.

Here is a picture from 10 days ago that showed something was wrong. It looked a bit like a nutrient problem or water... so be warned anyone whose tree looks like this, it could have fungus!
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Time: 31st December 2009 3:05pm

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About the Author Araich
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Araich says...
Here's an image of the tree today, 11 days after the image above.

The roots are still white and healthy but as a precaution I added more gypsum and altered the mound shape a little.

I would have once thought that this defolitation was the end of the plant but learnt from another hass that they can spring right back (in that case is was a water stress thing I believe).
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Picture: 2

Time: 1st January 2010 3:40pm

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Wayne says...
"Veins of the leaf are yellow it is over watering -Turn off the tap and apply Gypsum under the canopy and a dark pink solution of CONDYS CRYSTALS out to the drip line.
Veins green and the rest of the leaf yellow - Apply Magnesium sulphate(EPSOM SALTS) hand full per sq/m

That is an old rule of thumb Araich, however, looking at the difference in 11 days I must agree with you that it is an over watering problem. I think it needs some loving care and some fertiliser? now. The leaves in pic 1 certainly look like they are breaking down.

I certainly hope you can get it going again, once you do can you plant it out

Time: 1st January 2010 4:57pm

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amanda says...
Hi Araich, for what it's worth - I reckon your tree is suffering from a bad burn (either via sprays or fertilisers). In your first pic the plant shows a mild deficiency of an immobile element (youngest leaves yellowing) and a hooking under of the leaf tips.
Your next pic (2 leaves) shows the damage done (was this before or after the copper spray?) and the final pic the typical death of the margins. What have you been putting on it or in the planting hole? Maybe it was the copper/soap - did you stick exactly to the instructions or put in a bit extra/or more frequently spray?
I would be tempted not to stick anything more on it - just dilute seaweed solution until it re-shoots. Just my thoughts tho'.

Interesting about the yellow veins and overwatering Wayne! Didn't know that one. I have only ever found references to herbicide damage with vein clearing.



Time: 1st January 2010 10:51pm

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About the Author amanda19
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Wayne says...
We have a local gardening expert who has a show on ABC radio, he is responsible for the magnificent gardens around Rockhampton. He probably has forgotten much more than many of us know.

His name is Tom Wyatt, google his name with a question and see what you come up with.

http://www2b.abc.net.au/guestbookcentral/list.asp?GuestbookID=322&view=&numtoview=&start=&sort=&filter1=&filter1val=&filter2=&filter2val=&filter3=&filter3val=&advanced=&pagestart=8

That tree is still in a pot by the looks of it Amanda, so it would be easy to over anything if you are not carefull.

Keep us up to date Araich

Time: 2nd January 2010 8:10am

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Araich says...
You know I am fairly sure that it did not get over-watered as it would get just 1-2 litres during dry spells. It had a heavy mulch and was always damp beneath. Airflow was very restricted though and it would have been very humid in that enclosure on a hot day.

We are on dense silty clay and the hole was prepared down about 60cm (and 2m wide), then mounded up about another 40cm. Free-draining organic rich mix.

As far as I can remember I did not fertilise it. Having said that, tomatoes grow all around it, and I do remember casting about a cheap slow release and some tomato starter powder - but only up to that redish plastic tree ring in the first picture (which contained the last 15cm of the mound).

The roots still appear very healthy.

Reading that anthracnose description again I now wonder if I got it wrong.

Fertiliser burn? Could I have have done this!

The copper spray went on long after the leaves began to die.

BTW the yellowing between the veins was evenly spread across older and younger leaves, I thought. Which reminds me, I did give it a dose of iron chelates (after the yellowing was noticed).

What does the epsom salt do?

Time: 2nd January 2010 8:28am

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Araich says...
I should add that I have since removed the tree ring and brought the surrounding soil level up, with a compost/plain potting mix/gypsum mixture - as seen in the last shot.

And also, the rolling (hooking up) up of the leaves was one of the first symptoms along with the yellowing pattern. Then a darkening on the leaf along end, edge and in towards the center between the veins. Some reddish fine spots appeared. The leaves then began to brown only after some very hot days.

The dieback was different than the common browning of the leaf margins.

Time: 2nd January 2010 8:36am

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About the Author Araich
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Wayne says...
http://www.planetnatural.com/site/epsom-salts.html

Have a google around for epsom salts Araich

My apologies, I thought that ring was a pot. I don't think it is a fertiliser burn, just to much loving.

Do you happen to know your soil PH by any chance. I'm afraid I am not an avo specialist Araich

Time: 2nd January 2010 8:41am

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Araich says...
Oh dear. I decided to investigate the root system a bit more, as I'd only seen healthy white outer roots. I washed away the soil from the trunk back and you can see a reddish/brown colour around the crown - natural?

Digging around I could find dying roots, as pictured, though rare. The reddish fine roots broke away easily.

Anyone want to diagnose?

I rarely watered but it has had doses of heavy rain and would never have been on the dry side of moist.

PH is 6.5
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Time: 2nd January 2010 1:05pm

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amanda says...
Hi Araich, the white roots could be a sign that the plant is recovering (unless they are yet to die too) Try nicking a little bit of bark with your finger nail right down where the dark ring around the trunk is - just above the roots.
If it flakes off easily and is brown underneath then you could have collar rot or a stem canker.
It may also be due to overwatering like Wayne said - in that you may have poor drainage into the clay soil at the bottom - thereby creating bowl in which the plant gets too soggy?

There is also the possibility of Phytophora (dieback) in this situation :-(

Any other thoughts out there?

Time: 2nd January 2010 8:34pm

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amanda says...
PS Ariach..I hope u don't mind me being honest - but that soil looks really awful - it's a bit stagnant looking. Here is a pic I took of mine to capture good healthy wood eating fungal development. I had lousy soil - but this is 2yrs later and it's beautiful. Just a thought.
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Time: 3rd January 2010 2:08am

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Brendan says...
Hi Araich,
If it were mine, I'd add lots of gypsum around your tree, gently scratch it in, put the ring back, but have it sitting ON the ground, then mulch with a coarse mulch from the circumference of the ring, out as far as you can go, then give it a little drink of weak seasol (white bottle). By the way, the ring is there to stop the mulch touching the tree, therefore stopping root /collar rot. I noticed in one photo you had the mulch inside the ring, not good. Only thing to put inside the ring is, gypsum, composted cow manure (eg moo poo), and some potting mix.

Yates make a product called 'Anti-Rot', which is supposed to stop Phytophthora root rot. I don't think I'd try that just yet, as your tree is stressing. Wait untill it picks up, then try a weak solution of Anti-Rot, as a preventative measure.

Time: 3rd January 2010 7:56am

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About the Author Brendan
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Araich says...
Thanks guys.

Hi Amanda, the soil is actually more or less perfect for avocados. Free draining OM rich. It probably looks worse as the washing to clear the roots for inspection has left behind mostly the sand and woody pieces. It is far and away the best soil any of my pants have been given!

Brendan, that is good advice. The rings function for me was to support the last bit of the mound, I've since been able to bring up the surrounding soil to that level, in a steep mound shape. It worked really well with the plant filling it with healthy roots, like a pot with no bottom, and warm for the first winter. But that lucerne mulch should have been pulled back from the stem.

I've attached a photo of the bed a few weeks after planting (and another from spring). That corner spot was excavated (old tee stump) and filled with 2 trailer loads of free-draining top soil, with a deep point below the avocado.

I'm off the get some anti-rot now. I have a sick kiwifruit that looks like it may have fallen to the same heavy rains (and clay subsoil)...

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Time: 3rd January 2010 11:56am

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Brendan says...
Hi Araich,
Here's a photo of my avo tree planted in clay. As you can see, it's planted above the ground, with the ring. That coarse mulch is coco mulch from bunnings. (This photo was taken about 1 year ago.)

The mound was made up of gypsum, composted cow manure & cheap potting mix. What I did first, was dig a hole beneath where I planned to plant it, mix in lots of gypsum with the soil / clay, then put all this back into the hole :-)

You can see the 'soil' inside the ring is white with gypsum. The land is on ~ 15
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Time: 4th January 2010 7:34am

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amanda says...
Hi Araich - I just got my favourite book out from the library (Plant Nutrient Disorders - NSW Ag Dept) and am transcribing nitroge burn info for you - just in case. The pic is not so good as i took a pic from the pic in the book.


"Symptoms of fertiliser burn develop suddenly, often within a few days of application but, when fertiliser is not watered in injury may no be seen until after the first shower of rain. Leaf curl, defoliation, diebck and fruit drop are themost obvious effects. Sometimes leves develop translucent dark green damaged areas which later becom brown and dead. The lower leaves of young trees are usually shed first. Injury to roos... brown discoloured areas can be seen in the root fibre.."

In some ways it would be good if it's this - at least it will recover :-)
Anti-rot is not a nasty chemical - so it would be good to use as a preventative in your soil.

PS just added a pic of foliar applied spray burn. It really looks like nothing else..that's why i am convinced that's the prblem with your tree..time will tell I guess...good luck with it! :)
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Time: 5th January 2010 8:07pm

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About the Author amanda19
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Araich says...
Hey Amanda, thanks for doing that, the description is a good match. Is the second picture the nitrogen burn?

However there were no translucent patches on mine...

And, my young female Hayward kiwifruits have developed root-rot during the same period. I can pin it to rain as a neighbour who does nothing (no fertiliser or watering [been away] etc) has had their kiwifruit go exactly the same way.

One thing I have gotten wrong is not keeping the mulch away from the stem enough. I feel I have let the crown/collar stay wet too long. Adding iron chelates (more water) and seasol (more water) thinking it was an element deficiency, during a period of heavy rain has compounded this.

Add to that poor airflow and high humidity (thanks to a giant tomato and sunflowers on either side) and I've set myself up for fungi.

I am now even more wary of fertiliser but in this case I'm accept that over-watering (inc natural) and less than perfect drainage is the culprit.

The mulch is pulled way back, lots of gypsum added and I'm letting the mount dry out somewhat to kill any fungus. The shade/wind frame is now more open and I've cut back the tomato.

And encouragingly I can see new buds forming.

Time: 6th January 2010 8:33am

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Brendan says...
Hi Araich,
Have a look at this link that Brad from WA has posted:
http://www.agric.wa.gov.au/objtwr/imported_assets/content/hort/fn/cp/avocados/bulletin4484.pdf

There's a good photo of 'leaf-tip-burn' on an avocado tree. The 'guru' up here tells us to 'turn the ground white' with gypsum, if you have leaf-tip-burn, then apply lots of mulch.

Good to hear yours has new buds forming.

Time: 6th January 2010 10:21am

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amanda says...
Great Plant disease website:
http://www.ipmimages.org/
I use this one a lot (pic's are not downloading at moment tho')
It is free to join and has loads of pics and info on all sorts of things.

Here is a cupla pics of anthracnose on my grevillia. These are both misty pinks but the young one is unaffected at present. (As it doesn't bother them I don't worry about treating them).

The Abiotic damage has pics on drowning too Araich.

The stems, petioles and buds are all looking good on your avo' so if it's a fungus it's in the roots. I would be surprised myself tho' - they don't just go away without treatment (including root rot). As it's happening to your neighbour - then I agree with drowning too. The silt in soil is a bigger offender than the clay itself :-(
Let us know how you get on hey - it's all educational :)


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Time: 6th January 2010 1:12pm

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About the Author amanda19
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Araich says...
Hey all, despite the numerous 40C days here in Melbourne's west, my 1 year old Hass is slowly making a comeback.

As predicted it dropped all it's leaves.

I incorporated a large amount (perhaps 5-6 handfuls) of gypsum into the top 100mm of the mound soil, concentrated around the stem. Let it dry out, and have been slowly introducing water again to the mulched area + a mere splash around the stem. Dilute seasol once.

I'm 100% that it was a root-rot (too wet for too long) but also wonder if poor airflow and high humidity didn't add another fungi to the leaves.

Here's a few pictures from today.

[edit]On checking the ph again it came up as 6.5. It seems avocado like it slightly acid and root-rot likes it alkaline, so I sprinkled some Iron Sulphate around the mound, maybe 10 grams. I'm aiming for 5.8-6.
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Time: 1st February 2010 1:12pm

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Araich says...
The saga continues...

Well, those lovely new leaves started to darken at the edges and roll-up like the earlier mature leaves and shortly after all growth stopped. The leaves dropped.

I knew then that this was probably terminal and so after another month of it impersonating a stick, I've pulled it.

Washing the roots completely revealed that the root rot had continued, despite all my best efforts. Most of the fine roots detached while washing and I pruned the rest hard. The photo shows the result.

The branch tips have slowly been dying back, likely water loss and disease. I've pruned them back hard.

My plan is to leave the roots out over night to let them dry out completely. Pretty severe right?

Plant it in entirely new potting mix, with gypsum, in a pot and place it in a shaded corner.

I should probably just bin it, but I'm curious about the odds of it making a comeback from such a dire state.

Not a very happy tale so far I'm afraid.
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Time: 28th February 2010 10:05pm

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Mon says...
I also have a "sickish" avocado plant and am wondering if your plant eventually came good.
Cheers, Mon.

Time: 3rd August 2010 12:02am

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Jason says...
This entire thread just seems to be a case of death by over caring. Mon, they don't need anything special, just leave them alone, water when the ground gets dry and throw a bit of fertiiser on them if they have small leaves. If it's a very young tree it probably just has some winter blues.

But really all these copper sprays and gypsum and rararrar rubbish :). They are a big strong tree, they will look after themselves, especially here in a cooler climate that isn't able to host tropical soil diseases, almost all of Queensland is more out of an Avocados natural climate than Victoria is

Time: 3rd August 2010 2:45am

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