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Author Topic: twig dieback with gum at branch crooks  (Read 273 times)

brian

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twig dieback with gum at branch crooks
« on: November 03, 2018, 10:19:39 AM »
One of my fukushu kumquats has experienced signficant twig dieback in the past month or two.   This is the largest one I have, and the only kumquat I've planted in-ground in my greenhouse.  I noticed when cutting off the dead branches and inspecting the damage that there are blobs of gum at joints of the dead branches.  I've never seen this before, does this indicate anything out of the ordinary or is thjis common with twig dieback issues?

Now, I suspected the cause for the dieback was a rather severe cottony cushion scale infestation that I let go on too long while I fiddled with hose-end sprayers (I ultumately gave up and went back to a pre-mixed pump sprayer).   Its also possible that this is somehow related to the clay soil the tree is planted in, or the high humidity of the greenhouse.  However none of my other 40+ trees have this symptom, and many of them were infested with the same scale and sprayed for it at the same times. 

The kumquat is from Fourwinds, not sure which rootstock they used for kumquats.


« Last Edit: November 03, 2018, 10:26:43 AM by brian »

Citradia

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Re: twig dieback with gum at branch crooks
« Reply #1 on: November 04, 2018, 08:16:57 AM »
Iím trying to copy you a link: http://www.plantwise.org/KnowledgeBank/FactsheetForFarmers.aspx?pan=20147801443
Itís gummosis. From insect, mechanical damage, or disease. Most of what I see on internet about citrus gummosis is concerning phytophthora.

Citradia

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Re: twig dieback with gum at branch crooks
« Reply #2 on: November 04, 2018, 08:26:44 AM »
http://ipm.ucanr.edu/PMG/r107100411.html
Another link about treatment of phytophthora.

Sylvain

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Re: twig dieback with gum at branch crooks
« Reply #3 on: November 04, 2018, 11:44:00 AM »
Yes indeed, it is gummosis.It is a form of phytophthora attack.
You must treat your plant with Aliette (Fosetyl-Al), scrape clean the cancres and put copper sulfate (Bordeaux mix) on it.
If you do it now, it's OK. If you wait too long you plant will die.
http://citrusgrowersstatic.chez.com/web/viewtopic8295.php
 Or Google "gummosis site:http://citrusgrowersstatic.chez.com".


« Last Edit: November 04, 2018, 12:00:20 PM by Sylvain »

lebmung

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Re: twig dieback with gum at branch crooks
« Reply #4 on: November 04, 2018, 05:50:53 PM »
If you spray Fosetyl-Al on the plant, don't spray also with copper products, the are not compatible.
Drenching with Aliette (2.5 g/l) is effective in controlling the disease.
« Last Edit: November 04, 2018, 06:00:09 PM by lebmung »

lebmung

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Re: twig dieback with gum at branch crooks
« Reply #5 on: November 12, 2018, 07:15:02 PM »
Just one note more if you use Aliette or potassium phosphonate, both will turn into phosphonate acid with is effective to kill the patogen.
Bear in mind residues accumulate in plants even after many years. In Europe is was recently regulated it's use.

Millet

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Re: twig dieback with gum at branch crooks
« Reply #6 on: November 12, 2018, 09:18:09 PM »
It seems that everything that actually works is regulated in Europe
« Last Edit: November 13, 2018, 07:54:04 AM by Millet »

Ilya11

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Re: twig dieback with gum at branch crooks
« Reply #7 on: November 13, 2018, 03:41:31 AM »
Just one note more if you use Aliette or potassium phosphonate, both will turn into phosphonate acid with is effective to kill the patogen.
Bear in mind residues accumulate in plants even after many years. In Europe is was recently regulated it's use.
Where you got this information? Aliette (Al-fosetyl) is a very simple molecule that is  rapidly and completely eliminated both in plants as well as in environment.
« Last Edit: November 13, 2018, 03:53:25 AM by Ilya11 »
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lebmung

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Re: twig dieback with gum at branch crooks
« Reply #8 on: November 13, 2018, 04:29:15 AM »
Al-fosetyl indeed is a simple molecule which is absorbed fast by plants. Once inside it transforms into the phosphorous acid. This is the active ingredient which triggers plant release of chemicals to strengthen the plant. Also PO3 ions disturb the cell membrane of some fungi, including Phytophthora.
High values of residue were found in plants even after 2 years after the last spray which made the EU forbid the sale and use of potassium phosphonate as unregulated substance. In US it is used in organic farming. That was also the case in EU before 2013.
Phosphorous acid doesn't disintegrate into nature easily, and has no nutritional value to the plant.  But don't confuse with phosphoric acid which is used to regulate ph and its salts are used as fertilizer.
Here is the review.
https://www.efsa.europa.eu/en/efsajournal/pub/2963

Here is a research on apple
http://orgprints.org/13644/1/059-061.pdf
Just a note, potassium phosphonate yields the same results as Al-fosetyl. The later is a registered fungicide so it is presumed you know the risks and residues levels as with any other fungicide. While potassium phosphonate was sold as a plant strengthener and fertilizer.

https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2018.5161

https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2006.54r

« Last Edit: November 13, 2018, 06:09:33 AM by lebmung »

Ilya11

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Re: twig dieback with gum at branch crooks
« Reply #9 on: November 13, 2018, 09:02:08 AM »
//efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2006.54r[/url]
"Feeding studies carried out at similar exposure
levels demonstrate that residues of fosetyl and phosphonic acid in milk and other animal commodities
are below the LOQ of the method of analysis validated for enforcement (0.1 and 0.5 mg/kg for milk
and other animal commodities respectively)."
Also:
"Therefore no dietary risk was identified due to residues resulting from the use of fosetyl-Al according
to the representative uses in citrus, grapes and cucumbers supported by the applicant."

https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2018.5161
"Adequate analytical methods for enforcement are
available to control the residues of fosetyl-Al and phosphonic acid in plant matrices under consideration.
EFSA concluded that the proposed use of fosetyl-Al on potatoes and the proposed uses of potassium
phosphonates on pome fruits and peaches and the authorised use of potassium phosphonates on tree
nuts in the United States are unlikely to result in a consumer exposure exceeding the toxicological
reference values for phosphonic acid and fosetyl and therefore are unlikely to pose a risk to consumers
í
health."
« Last Edit: November 13, 2018, 09:29:08 AM by Ilya11 »
Best regards,
                       Ilya

lebmung

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Re: twig dieback with gum at branch crooks
« Reply #10 on: November 13, 2018, 11:50:19 AM »
You didn't add everything.
"However, the risk assessment is considered to be tentative and has to be updated as soon as the approval of the renewal of fosetyl and the review of existing uses of potassium phosphonates and disodium phosphonate is finalised"

Anyway fosetyl-al is not forbidden, I just say that they found that it leaves residues especially in the leaves and wood of the plants many years after exposure. I think this substance need more studies.

For me I would use it with caution especially after flowering and while bearing fruit.

Ilya11

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Re: twig dieback with gum at branch crooks
« Reply #11 on: November 13, 2018, 01:28:33 PM »
It is probably the safest of all imaginable fungicides. Phosphorous acid is a natural compound occurring in the environment.   
Best regards,
                       Ilya

brian

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Re: twig dieback with gum at branch crooks
« Reply #12 on: November 13, 2018, 02:30:20 PM »
I just noticed all the replies to this thread.  I discovered I actaully have a few other trees that have the same symptoms.  I have some Agri-Fos that is probably four years old - does it go bad? 

brian

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Re: twig dieback with gum at branch crooks
« Reply #13 on: November 13, 2018, 02:44:50 PM »
I ordered some more.   FYI its now called "Garden Phos" and no longer Agri-Fos

 

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