Treating Phytophthora citricola in avocado

Phytophthora Canker (Fusarium????) and Crown Rot (Citricola Canker) in avocado tree trunks

1/28/2016: I have taken several samples of this tissue to the University of Florida Plant Clinic in Homestead trying to confirm what I suspected: Phytophthora Citricola. The first set of samples nothing grew in the phytophthora media. A new set of samples checked in a broader media indicate this disease is fusarium. Not sure the type since it has to grow more to get DNA to be able to identify. Now I'm really not sure how to treat.
2/4/2016: A few days ago Randy C. Ploetz Ph. D. came by the grove and he obtained samples from 4 different trees with this canker. He notified today that preliminary indications is that it is Phytophthora cinnamoni. Which is more in line with the symptoms. At this point I can continue to treat with Phos Acid

Reminder to everyone. This pages are for my own research, it is simple for me to place and organize research in a web format. Treat it as such. I do not endorse any treatment or product. Treat it for what it is, you are a visitor in my grove and this is what I'm doing. I would welcome any comment on the subject specially from growers. Use the contact form in this pages.

Crown rot in avocado tree 52-4, click to enlarge

I'm going to document in this page my handling of various types of crown rot in my avocado trees. I'm beginning to observe that about 10 percent of my trees have some form of it. From looking at what I have, seems like I have a combination of types from the very clear "Phytophthora canker with regions of dark bark that often exudes red resin", as shown in the picture to the left, clear red spot in the center of picture.
I do have others no so clear to identify. I will start by posting an album of pictures with the different variation. (at the bottom of the page) Each tree has been identify and I propose to do something about it in the next few months. here is a very good article from UC Davis on this: Click here to see it. Another good article form UC click here. There is not a lot of research on the subject.

Planning on how to proceed I'm inclined to do 3 different protocols.

Clean the outside of the area, remove dead tissue and do a localized spray of 8.0 oz of Phosphorous Acid 8.0 oz and .5 oz on Pentra Bark. Referred to as PAS (phosphorous Acid solution)
Do the cleaning as 1. and apply Tree Bandage product to the area.
Do no 1. and after a week or so apply the Tree Bandage product..

Good articles and research

November 28, 2015 Today I stared to do the first step I wanted to do. To remove as much of the dead tissue as possible. I did two trees, No. 52-4 and 52-7. I was very surprised at the amount of disease that is inside the trunk. It is like an iceberg, what you see outside is a small part of what is inside the tree. I will separate each tree in its own section. The image to the left is go give an idea of the location and depth of the lesions. In these two trees, the damage gets into the sapwood of the tree and moves in the areas between the growth rings and inner bark. Tree 52-4 was not too bad but 52.7 was really bad. There is no way to clean the canker without damaging or killing the tree. There has to be another way. I applied PAS to both trees in the exposed areas and lower trunk. Will probably try Alliette in some trees as well with less debridement. Let's see if these two trees survive

Tree 52-4 Phytophthora, Crown Canker

Clearly the tree has the red resin associated with this disease. This particular tree has a clear red spot visible from the outside, more on the inside, it did not look like much but when I started to remove dead bark and try to clean the sick tissue realized it is far reaching inside the tree and to areas not visible from the outside. I also dug the soil around the base of the tree to be able to work. Did not see disease bellow 1.5-2.0 inches bellow ground level. I was not comfortable continuing to remove sick tissue I left it as shown in the picture to far right. Some of the dark spots you still see are over 2" inside. Applied PAS. Click on the pictures to expand.

Tree 52-4 before clean up process

Tree 52-4 Early process of cleaning sick tissue, the dark part in the center is resin.

Tree 52-4 after clean up before applying the PAS solution

Tree 52-7 Phytophthora, Crown Canker

Tree 52-7 has canker damage in about 75% of the circumference. I did as much clean up as possible and applied the PAS. Seems to me that if I cleaned all that I could have I would have killed the tree. There is more to find out about this disease since it does not seem to affect the tree's health so far. Both of today's trees looked in very good shape. I need to regroup and change the protocol to a less invasive one. (Click on the pictures to enlarge) a second application of PAS was done on November 30, 2015

Tree 52-7 before clean up process

Tree 52-7 after clean up

November 30, 2015: time to regroup. It is clear to me that cleaning up or debridement I did in the above two trees. Seems to me that I need to check if minor debridement and basal application of fungicide can be a good control method. Thinking about this I realized that over the last 3 years I have injected some trees with phosphorous acid, I set out to find some of these trees with Collar Canker to see the effect of the injection on the collar canker. I located two trees

Tree 75-17 Avocado Donie Phytophthora, Injected with Phosphorous Acid on December 2014

This tree had quite a bid of dead tissue but the canker seemed to be under control I did not see any exuding red fluids typical of active canker. Eleven months post injection and the canker seemed under control. I did a very minor debridement and spray some PAS to see if that would extend the sanitation of the wound. The video shows the clean up process and condition post injection.

Tree 75-17 Phytophthora Citricola canker. Nov 30, 2015 prior to debridement of dead tissue

Tree 75-17 video of light debridement process and application of PAS

Tree 3-14 Avocado Dupuis Phytophthora, Injected with Phosphorous acid September 2013

This tree is about 27 months post injection. The tree looks wonderful and the collar canker is moderately active, you can see some healed areas but in other looks like it is coming back not with force or never went totally away. The tree was cleaned and some PAS applied. What I gather so far is that the injection works for at least a year but will loose effectiveness on collar rot after 24 months. This is where basal control applications can come in handy.

Tree 3-14 Collar canker injury on November 30, 2015. Prior to debridement. Click on picture to enlarge

In this video I show how a collar canker looks 27 month post phosphorous Acid injection.

December 2, 2015: Today I will do a few trees with Collar Canker that have not been injected before. Just some minor debridement and a PAS made of of 1/3 PA, 2/3 water and 1.5% Pentra Bark or 2 qt. PA (Kphite7) 1 gal of water and 3 oz Pentra Bark. This will give me an idea of how many trees I can treat with this solution. For now this is what I will be doing.
I was able to treat 30 trees with the above solution, not only basal but 2-3 ft up the trunk. 1 1/2 gallons very cheap to do under $7.00 for the products and can be done in one 1/2 hour or less. I did checked 4 trees with clear collar canker visible by removing some of the dead bark and looks very encouraging. Only a couple of small wet spots, clearly that ground application of phosphorous acid via the irrigation system have been working.
Summary: All 30 Donie Avocado trees in section 19 treated with the spray. Trees 3, 9, 11 and 17 dead tissue removed and inspected. Video taken of 3 and 9. Trees 18,20,21,22,26 and 29 showed evidence of having collar canker. Some issues of precipitation with Kphite7, white semi solid matter, appears not too compatible with Pentra Bark. They do not have a label for basal application so I would discontinue to use it. Rampart Fungicide has injection but not basal application. I may do a jar test with Rampart but I'm expecting some Reliant Fungicide in a few days. (not done got some Reliant Fungicide)

VideoTree 19-3 examination and debridement December 3, 2015

Video tree 19-7 examination and debridement December 3, 2015

December 3, 2015: I will wait for the Reliant to arrive and in the mean time I will pick 10-15 trees with a bad case of canker to do just basal applications with Reliant Fungicide. Rampart is out of the local CPS.

RECORD OF BASAL SPRAYS PER SECTION AND DATES

DECEMBER 3, 2015: Donie Section 19 done Kphite basal spray
DECEMBER 12, 2015: Arue Section 7 and Dupuis Section 1, 1-9 Reliant Basal Spray
DECEMBER 16, 2015: Dupuis Section 1, 9-30 and Donie Section 21-22 all 60 trees. Reliant Basal Spray
DECEMBER 18, 2015: Donie section 23 all trees Reliant Plus Im 1/2 ml per gal Basal Spray
December 20, 2015: Donie section 24, Arue section 8 and Dupuis 2 all trees Reliant Plus Im. Basal Spray
DECEMBER 23, 2015: Arue section 9, Dupuis Section 3 all trees Reliant Plus Im. Basal Spray

January 19, 2016: The two videos below are of tree 54-3 This tree was cleaned up and a sample of the dark part with the red exudate taken to TREC's Plant Clinic to see if they can determine the actual pathogen causing this. The tree was treated with two application of Phos Acid spray with Pentrabark to the affected areas.

January 19, 2016: Section Donie 96 Phos Acid Basal Spray
February 2, 2016: Arue Section 10 and Dupuis Section 4 Basal phos acid Spray