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Avocado Disease Identification

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Justin starts with ...
I have just noticed that two of my avocado trees (about 4 years old) have lots of branches with splits in them - it's like the outer layer of the branch has split, and all around it is a white powdery substance a bit like chalk dust. Inside the split, the branch has a brown patch.
Otherwise the trees have been healthy up until now, and one is just starting to produce fruit.

Any idea what this is, how serious it is, and how to treat it?

Thanks.
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Justin
Melbourne
20th January 2012 2:47pm
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Peter says...
Justin,
can you do a fresh cut just underneath the split area and take a picture? Also have a smell, if there is a fruity odor. Lets go from there...
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Peter36
Perth
20th January 2012 11:59pm
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Brendan says...
Hi Peter & Justin, for what it's worth, I had an avo branch twice as bad as in the photo. I showed it to Jerry Colby-Williams (from ABC Gardening Aus.) when he was in Mackay. He said, 'your tree has a cold.(?) Spray with Fungus Fighter until it clears up.'
Fungus Fighter is copper hydroxide. I use copper oxychloride.
Try making a paste with either of these and cover the affected area. It should clear it up. If not, cut it off and burn it, or bin it.
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Brendan
Mackay, Q
22nd January 2012 9:15am
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Original Post was last edited: 23rd January 2012 8:01am
Mike says...
The white powdery substance like sugar is just dry sap and mine have spots with it also.I have seen something similar before that did not cause any asting problem.Brendans treatment sounds pretty good and mancozeb also might work.
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Cairns
22nd January 2012 2:27pm
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Peter says...
Still it would be very interesting to see the area underneath the splits...
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Peter36
Perth
24th January 2012 6:24pm
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Brendan says...
Have to agree Peter, it would be very interesting under the bark.
It looks like either Dothiorella Canker or Phytophthora Stem Canker, mine was the latter I suspect. Because we had a ship-load of rain when my seed-grown 35 year old avocado tree had this, it ended up dying :-(
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Brendan
Mackay, Q
25th January 2012 10:08am
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Original Post was last edited: 25th January 2012 10:26am
Peter says...
Yeah, if we can distinguish between Dothiorella and Phytophthora it would be very good. Both require different treatments. Even Phytophthora is often called a fungus, this is not the case (more related to a group of algae) and will therefore not respond to fungicides. But it will to Phosphite. Application of both at the same time is not recommended.
I straight away believe that Mike have seen the same, but it did not cause problems for him - soils in Queensland are in general very suppressive to Phytophthora (if soils are not waterlogged during warm weather). However, the same disease can be more severe in Melbourne soils - they certainly are more in WA compared to Queensland!
So still we need to establish if Dothiorella or Phytophthora.
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Peter36
Perth
25th January 2012 11:08am
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Robert says...
I have a Haas tree and the leaves are turning brown and crispy I was told that maybe it had to much salt. So I repotted it today and found the soil was very wet. While repotting I tore half the roots getting it out of the plastic pot that it came in. How much did I hurt this tree or do they bounce back. Thanks for any help
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Robert12
Corpus Christi Tx
25th January 2012 1:42pm
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amanda says...
Gee Robert - that doesn't look too good :( One of the Avocado folk here may have some good advice. Dilute Seasol is useful to help with any transplant shock? I wouldn't give it any other fert's just yet - maybe wait till u see some new shoots and then try a little blood and bone.

Hopefully it will recover. It might just be a waiting game now.

Avocados hate salt - so ask the guys here what they use for fertilising in pots?

(ps - have u been overwatering it? It may also have developed a root rot.. :(
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amanda19
Geraldton, 400km North of Perth
25th January 2012 3:41pm
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Original Post was last edited: 25th January 2012 3:42pm
Mike says...
I didn't want to use the P word.It often manifests as yellowing,loss of turgor and dying of limbs in avos with trunk cankers sometimes forming.In NQ avos in wet areas are pretty prone and it can be an absolute shipfight every wet season.All the same I have seen that condition and just assumed it was not P.The response to fungicide may have been coincidental in cases I've seen.
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Cairns
25th January 2012 7:21pm
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Peter says...
I am not sure what you mean, Mike.
Anyway, at this stage it would be good to have Justin back. Are you there, Justin?
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Peter36
Perth
25th January 2012 7:33pm
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Mike says...
Peter,by P I mean Phytophthora and avos struggle here every wet season on the coast.The similar problem on my avos which cleared after coppy oxy/mancozeb coincided with the end of the wet season.Perhaps it was phytophthora with different symptoms to that of avo trees that I have seen die of the affliction.If there is any doubt pretty regular phosphite application might be one of the only courses of action.
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Cairns
25th January 2012 8:00pm
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Peter says...
Thanks, Mike.
Could be that you cleared up only the secondary invaders feeding on the dead tissue caused by Phytophthora (which as a primary invader moves on to more intact tissue) and the end of the wet season was certainly better to get rid of these fungi.
Maybe though it was Dothiorella.
I was thinking of P. citricola, which has different symptoms to P. cinnamomi and does not necessarily cause tree death.
One of the weird things of this forum when it gets to diseases is that the original enquirer disappears, whilst contributors entertain themselves.
By the way: thanks Brendan for the pictures.
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Peter36
Perth
25th January 2012 9:25pm
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Original Post was last edited: 25th January 2012 9:26pm
Mike says...
That could be the case Peter and the Phytophthora may have been cleared by subsequent and repeated doses of yates ant-rot.There could be a low level of 'infestation'in many trees waiting for a trigger.In the absence of the original enquirer giving more info. it isn't such a bad thing to speculate and share relevant experiences.
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Cairns
25th January 2012 9:40pm
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Peter says...
Yes, overall a good share of experiences on a daily (daleys) basis...

It feels a bit risky sometimes to speculate though, some just wait out there to get you, if you're wrong.
For Robert: Amanda summed it up well - and hopefully it was just salt stress. Just keep an eye on it and keep it less exposed to direct full sun while the plant adapts with being transplanted
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Peter36
Perth
26th January 2012 12:18am
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amanda says...
Hey Peter..I'm glad u said that - the first thing I always do with a sick plant (if in a pot) is get it out of direct sun (if summer) - stressed plants just don't need the extra stress of even more fert's and hot/direct sun?

I would be interested to see if this plant survives actually....(if it were something more robust maybe) do u think Peter?

I agree tho - sometimes it just a waiting game. It can be really hard to speculate on just a photo too..so many variables. I am not sure that people should expect definitive advice here, myself.
The forum has become a bit of a "problem solver" over the last cupla' years...I am not sure that was it's original intention?

I am very loathe to offer advice on mature trees, for eg, myself. I am not a professional by any means (and don't carry indemnity insurance! lol..)

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amanda19
Geraldton, 400km North of Perth
26th January 2012 12:48am
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Original Post was last edited: 26th January 2012 6:55am
Brendan says...
Hi Robert, our garden guru here was asked a similar question as yours not long back, here's the Q & A's.

Q. Avocado tree lost leaves & was dying but recovered after a few heavy doses of copper oxychloride solution. Now new leaves are beginning to brown & burn at the tips, what could be the problem?

A. Apply Claybreaker to the soil, this is a liquid. 250mls to 4.5 litres of water apply three times seven days apart. This will displace any toxins.

(She then explained it was growing in sandy soil) So Tom replied:
Most likely salt injury, apply Gypsum four clenched handfuls per sq metre around the area, this will be required twice per year.



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Brendan
Mackay, Q
26th January 2012 11:40am
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Justin says...
Here are some more pictures.
So far I have treated with Bicarbonate of Soda and Manuka honey - until I can get the chance to get some Copper hydroxide. There has been a little improvement, but not major as you can see.

We also had a hailstorm on Christmas day - not sure if the splits were caused by the hailstones and this is an infection of those injuries, or whether the splits were caused by disease.
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Picture: 2

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Justin
Melbourne
28th January 2012 3:31pm
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amanda says...
Justin - did u take the pics b4 or after the bicarb applications?

(sorry - I know that sounds dumb - but just wanted to check..)

Also - would not consider pruning those branches off b4 the pathogen spreads?
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amanda19
Geraldton, 400km North of Perth
29th January 2012 12:06am
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Original Post was last edited: 29th January 2012 12:10am
Peter says...
Hi Justin,
I think is looks more like a mechanical damage (and you mentioned the hailstorm)with then some fungi takeing advantage of that, but it seems very restricted to the area. So fungicide application what Brendan recommends would be good.
Overall your tree looks in good health.
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Peter36
Perth
29th January 2012 1:18am
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amanda says...
hey Peter - will the damaged areas just get re-infected though?
I was always under the impression that diseased, damaged and dead branches should always be pruned on any trees...? (not disagreeing with u guys - just curious :)

(pic 2 looks particularly nasty - will the tree be able to heal a wound like that..?)
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amanda19
Geraldton, 400km North of Perth
29th January 2012 11:52am
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Original Post was last edited: 29th January 2012 11:54am
Justin says...
Thanks for the advice, all. My second lot of pics were taken after the bicarb and honey.

I considered pruning off the affected branches, but almost all branches are affected to a certain extent, and the trunk as well, so I'd have no tree left if I did that.
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Justin
Melbourne
29th January 2012 1:11pm
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Bunya Paul says...
My Haas fruited heavily last season so this season has not. I have taken the opportunity to do some major pruning in this off year to fix the fact that I let the main lateral branches grow too low on the tree, meaning the fruit hangs to the ground. Pruning included sawing off some branches that were several inches in diameter. Straight after sawing I brushed the wounds with that black pruning paint but soon after it had dried I notices sap from the plant was getting through the paint. This wet sap was soon replaced by a white powdery looking substance that I had assumed was some sort of fungus - bringing me to this thread when Googling for what I should do (which was apt given I have bought all my Avo plants from Daleys. The white powdery stuff is on the big and small prunings all over the tree. After reading the above thread I came across the below youtube link which I am pretty sure explains my particular issue - worth others taking a look at. https://www.youtube.com/watch?v=OgvD7tzorKM
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Bunya Paul
Bunya
20th December 2015 8:44am
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Original Post was last edited: 20th December 2015 9:03am
Justin1 says...
Thanks, all. And thanks for the video, Bunya Paul - it seems to explain the origin of the white stuff. Here are some more pictures 4 years on - the wounds haven't healed over as I would have expected, but the tree itself doesn't seem to be affected (and is bearing well).
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Justin
COBURG,3058,VIC
22nd December 2015 10:59am
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Silent Bob says...
HI,

Does anyone know what is happening to my avocado tree and how should I treat it
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Silent Bob
Rochedale
12th December 2017 10:22pm
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Fruitylicious1 says...
Hi Bob

Where is the picture and or description of your ailing avocado tree?

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Fruitylicious1
TAMWORTH,2340,NSW
13th December 2017 8:59pm
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Original Post was last edited: 14th December 2017 6:37am
Silent Bob says...
Hi , for some reason this pictures didn't upload with my post. I'm worried about my only tree. I've only had it for 5 months and it doesn't look too healthy. My local nursery suggest I treat it with Searles Root Rot. Any advice would be great. Thanks
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Silent Bob
Rochedale
14th December 2017 10:14am
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Justin says...
Looks similar to what happened to mine (sunburn). Are the damaged bits facing the sun or is the damage all the way around? The stems are very sensitive to the sun - high UV-index days can do it, even when the temp isn't that hot. Mine recovered but were already quite big and the lesions were not around the whole branch. If the wounds totally encircle the trunk of your tree then it may cause ring-barking which is going to have a pretty poor outlook.
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Justin
Brisbane
15th December 2017 11:00am
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Bryantree says...
I hope I’m not hijacking this thread. I just noticed this happening to my pit grown tree. This leaf was stuck to the trunk and underneath was this.
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Bryantree
Raleigh
8th January 2018 1:39am
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Fruitylicious1 says...
Hi Bryan

Did you by any chance forgot to upload a picture of your pith grown avo tree for disease I.D.?

Happy Gardening :-)
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Fruitylicious1
TAMWORTH,2340,NSW
8th January 2018 3:51pm
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Bryantree says...
Here are the photos again
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Bryantree
Raleigh
9th January 2018 5:41am
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Bryantree says...
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Bryantree
Raleigh
9th January 2018 5:42am
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Fruitylicious1 says...
Hi Bryan

Your avo tree might have caught P.Citricola infection. which is the most common fungal disease among avos (around 90%). Unlike the more sinister pathogen P. Cinnamomi where death is imminent if left untreated. The most common symptoms are: often there is sugary exudate (bleeding) with a distinct pocket of wet dead tissue below the damage bark. This white exudate often dries up to form a white crystalline deposit on the bark.

Moderately affected trees often appears quite healthy like yours and may persist this way for several years until the canker progresses to a stage where it may start killing the cambium tissues around the trunk accelerating the eventual demise of the tree.

I can see from the picture that there was a decapitated branch scar where the infection started. It might have been shielded by a leaf and didn't have the chance to properly dry up and heal and might have been unwittingly rewetted hence aggravating the infection.

Treatment of this disease starts with scraping of cankerous tissues to remove active cankers and painting the area with copper bordeaux. But this treatment has limited success among growers. The most preffered treatment among growers recently is the immediate treatment of Aliette systemic fungicide from Bayer, or neutralised (buffered) phosphorus is more likely to reduce potential infection than using copper bordeaux after tree surgery. Another effective treatment is the application of Ridomil Gold 480 SL by Syngenta. As always follow manufacturers recommendations and always protect yourself with appropriate PPE when handling chemicals.

Happy Gardening :-)
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Fruitylicious1
TAMWORTH,2340,NSW
9th January 2018 10:18pm
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Original Post was last edited: 11th January 2018 9:12am

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