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HELP! Phytophthora Root Rot Plum Trees

natschultz
14 years ago

Hello,

I am in DESPERATE need of help!!!

Last Spring I purchased 3 plum trees, a Nectarine and 3 Blueberry bushes from a reputable fruit tree nursery (I've never had problems before).

Everything seemed fine at first, but towards the end of summer all the plums started dying, and one of the blueberries as well. They did not need water, although they appeared to be suffering from drought. By the fall they were dead.

I left them all until this spring, hoping they might come back. The plums are all dead, as is the one blueberry; another blueberry appeared dead, although it now seems to have a bit of new growth coming from the roots.

The 3 blueberries were planted in one large 6'x6' raised bed, with a lot of OM and fresh topsoil. One of the blueberries is fine - all new growth on the entire plant (no obvious dieback).

The 3 plums were all planted separately - 2 in 20 gallon pots (temporarily) with fresh soil, the other one planted high on the ground (about 6-8" above grade, after I amended the soil beneath, mounding fresh topsoil mixed with the native soil approx. 3 ft x 3 ft wide mound. Nothing else is planted near that plum for at least 5 feet.

The plants in the ground have newspaper (starting ~9" from plants) and heavy cedar mulch to keep out weeds and hold moisture. I never had to water much at all after the first 2 weeks.

As I said, the plums started dying towards the end of summer, but they had plenty of moisture in the soil, so I just used some organic fertilizer to give them a boost, but by fall they were all dead. The one blueberry succumbed to the same fate.

This spring I just removed the potted plums, without much thought, but yesterday I dug up the planted plum and analyzed the roots. They were dead and had NO FEEDER ROOTS at all!!! There were two earthworms embedded near the crown in some remaining soil, as well as some of those tiny white wiggle worms. I think these guys were eating the dead roots - not the cause of death. I cut one bit of root and the inside was a redish-brown.

I thought it could be nematodes (root lesion), but now I really suspect Phytophthora Root Rot.

Beacuse they were all planted separately in fresh soil, and all succumbed to the same fate, and they were all shipped in one box, I believe this disease was sent to me from the nursery.

I plan to contact the nursery about this, but now I'm deathly afraid to accept anything from them.

Oddly, the dwarf nectarine seems fine.

My question is this: What do I do about the soil? I was going to plant a Black Mulberry in place of the plum in the ground (I was going to replace an invasive White Mulberry with the black one, but I read that the invasive (Asian) white mulberry roots carry a pathogen that kills Red Mulberries, so I'm not taking any chances).

At this point I am willing to drench the soil with chemicals to kill this evil root rot, because it can spread to my Rhodis, Azaleas, Pieris and Mountain Laurels - I have TONS of those in my yard, and I cannot allow this deadly pathogen to spread to them.

I was thinking of removing all the mulch and soil from the mound and cooking it in the oven, but this would take a very long time. What about a bleach solution? I cannot afford to buy all new soil. I will add some sand into the soil to speed up drainage though. My real fear is that I have carried this pathogen around my entire yard on my shoes. I can disinfect my tools, but I have no idea where else it has spread to by now.

Is there a good fungicide that I can get at Lowes / Home Depot that will kill this in the soil? I do not want to plant my Mulberry until I have treated the soil. I will add some fresh compost after treatment to get the good organisms back.

Honestly, I just want to die after this discovery! I am SO AFRAID that it will spread to my broad-leaved evergreens and my oak trees.

Any advice will be greatly appreciated! Thanks.

Comments (5)

  • natschultz
    Original Author
    14 years ago
    last modified: 9 years ago

    OK, after reading through TONS of info on Phytophthora treatments I finally found a solution (other than restricted fungicides I cannot buy) that should work on the soil!

    I found this in-depth research project done in the UK:
    http://randd.defra.gov.uk/Document.aspx?Document=ph0320_7378_FRP.pdf

    Essentially, the only thing that works on soils and composts is to fully saturate them with a 10% bleach solution for a minimum of one hour (best during cool temps). Anything less and the pathogens are not killed because the other organisms destroy the disinfectant.

    I guess I'll start shoveling the mulch and dirt into wheelbarrows and saturate it with the bleach solution and then lay it out on a tarp to dry. First I will take a soil sample to have tested by Cornell (along with the dead trees).

    Note: this only kills the pathogen in the soil - it does NOT kill the pathogen once a plant is infected!!!

    Here is a link that might be useful: Detection and decontamination of Phytophthora species

  • jean001
    14 years ago
    last modified: 9 years ago

    That article is about Sudden Oak Death, not about a root rot. Two very *different* Phytophthora species.

  • jean001
    14 years ago
    last modified: 9 years ago

    Oops.
    I meant to add that, if the problem is root rot, the only "treatment" in a garden or landscape is to plant something that is resistant to the disease.

    That said, overly wet soil kills trees. The end result is the same as for root rot -- no viable roots and those roots that do exist are black.

  • frank1965
    14 years ago
    last modified: 9 years ago

    I'm glad you are getting them tested- without a test it is pure speculation as to what killed them. Also, if they died last year it is possible that the feeder roots have decayed by now. Feeder roots are small and delicate and wouldn't take long to rot away. Please let us know what the test said.

  • natschultz
    Original Author
    14 years ago
    last modified: 9 years ago

    Hi again,

    Ok, I contacted my local Cornell Extension, and they cannot do the test (they don't have that equipment) - it must be mailed to the Cornell Plant Disease Diagnostic clinic.

    I explained what happened, and she does not think it is Phytophthora, because according to her the soil would have to be excessively wet "almost like a bog." She does not think it is worth having tested because they have been dead too long and other organisms may screw up the test.

    Now, everything I have read says it spreads in "wet" soil (not just "almost like a bog"), and that one of the main ways it is spread to new areas is through nursery stock.

    She thinks the trees "Just didn't take." Very odd, in my opinion.

    The fee for each test is $40, and each test (mold, fungus, nematodes) is a separate fee. I don't think it is worth it, since it has been too long.

    I'm going to call the nursery and explain what happened and ask them if they have certification proving they do not have Phytophthora.

    I already removed the mulch and soaked it in a 10% bleach solution, and when I removed the soil from the hole there were at least 100 earthworms in it, so I picked them all out and relocated them to another area of my yard that is pure clay that I've been amending with leaves and pine needles (nothing planted there yet). I'll soak the soil that was immediately around the tree in bleach, and then till the rest of the area and add a lot of compost and some sand for drainage. The plum was already planted above-grade, but I'll plant the mulberry even higher. I figure better safe than sorry and bleaching it is the safe way to go (my book on diseases says to throw the soil out - but that will only spread it to a new area!).

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