Black Walnut Defoliation ???

Discussion in 'Lawn Mowing' started by EJK2352, Sep 7, 2003.

  1. EJK2352

    EJK2352 LawnSite Bronze Member
    Posts: 1,150

    I have a couple of properties w/ Black Walnut tree's. For about the last 3 weeks they have been dropping leaves like mad. They are almost completely defoliated now. I had one customer ask me why they are dropping so early and she thinks the tree is dying. She thinks the tree is getting drowned and it is causing the tree to die. We have had a ton of rain this summer and maybe she's right??? I don't know but I told her I think it's a disease problem brought on by the damp weather. I promised I would get her an answer ASAP. Anybody have any idea what I am looking at here???
  2. 1MajorTom

    1MajorTom Senior Moderator
    Posts: 6,074

  3. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Walnuts can lose their leaves very early, compared to other trees. I have one that I use as an indicator of how fall will progress. This tree starts to lose its leaves usually around the end of August, and is bare by the end of Sept, before any other leaves fall. One year it was bare by mid-Sept, and I knew fall would be early.

    This year this walnut was losing leaves in early August, actually had to rake leaves before mowing in 2nd and 3rd week of Aug. But then leaves stopped dropping. Still has about 40% of its foilage, but I expect them to drop soon. Because of the rains this year, it probably had brown leaf spot (didn't bother checking, because property was sold end of Aug).

    Brown leaf spot is characterized by irregularly circular dark brown or blackish spots. Also, walnuts are susceptable to yellow leaf blotch; looks like yellow blotching on upper side of leaf and snow white coating of fungal growth on underside. Main control for both is sanitation: clean up and dispose of fallen leaves. If client is attached to tree, have them contact a reputable tree service for treatment next year - will need 3 applications for most effective control.

    Your trees probably just had more infection than normal because of the wet spring and early summer. Most leaf spots infect leaves as soon as the buds open. Rains splatter the infection to other leaves. Leaves dropping now are just from that spring infection.

    And leaves dropping does not mean a great problem. Most trees can stand 2-3 complete defoliations in a season without fatal consequences. Defoliations from leaf infections like this are common - look at some old crabapples => seems they drop more leaves than they could have, LOL. Now, if leaves die and stay on the tree, you could have a real problem.

    PS, In Jodi's link the walnut anthracnose is the same as my brown leaf spot, and Microstroma white mold is same as yellow leaf blotch.
  4. EJK2352

    EJK2352 LawnSite Bronze Member
    Posts: 1,150

    Thanks for the info. Jodi and Jim. I am going to take a close look at the leaves and see if I can determine if it is a disease. That is a great link Jodi and should help me identify if it is indeed a disease problem.

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