Arbutus seedling still wilted & spotty

Discussion in 'Garden Pest Management and Identification' started by fern2, Apr 26, 2006.

  1. fern2

    fern2 Active Member

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    Hi,

    I posted here last year about one of my arbutus seedlings that had started to wilt & get spotty leaves. Well, that poor little plant has never really perked back up and, despite some ups & downs over the past year, its leaves are getting more spots & holes than usual (apparently, spring is when many of these problems tend to worsen & spread).

    I know it has a low-level aphid infestation but I pick them off every couple days (& put ladybugs on to feast when I can), so they can't be having too much of an impact on the tree's health. And I can't see any other insects on it. The clay pot does have a small amount of white powdery mildew (I assume) on its outside, which I have to find a way to deal with - but then the other 100% healthy tree has that too, so I wouldn't think that that's the reason why the bigger tree is looking sicker than usual now.

    The leaves are probably the best source of info about what's wrong with the tree (its stem looks fine): many of them have small black spots (not raised or pitted), often in little clusters; some look like their edges have been chewed away; some have medium brown spots where it looks like someone/something ate all the fleshy part of the leaf & left only the skeletal structure; and many of the leaves, especially the larger &/or most afflicted ones are unusually brittle.

    I've read through 'The Decline of the Pacific Madrone' book, particularly the chapter on diseases, and have looked at various other online sources, but I can't find any fungi or bacteria that produce the symptoms I'm seeing here. Part of the problem is that most books etc don't have enough photos or descriptions. So I'm hoping someone here can look at the attached photos and help me diagnose what's ailing my tree.

    What's so weird is that, at the same time that it's looking so poorly again, this tree is also happily producing new buds and is about to pop open some new leaves at the top of its central stem. I've been told that it wouldn't be making new leaves if it was really sick, but I'm still concerned.

    Does anyone recognise the fungi or bacteria (or insect) that's having such a negative effect on my seedling? And if so, do you have any suggestions for how to kill the pest (or at least minimise its damage) without killing the tree? I know that Arbutus are VERY susceptible to fungal & bacterial infections, and that there isn't a lot you can do about most of them, but I'm crossing my fingers that my tree is infected (or infested) with something I can fight.
    I'd be very grateful for any help you can offer. Thanks.

    (and yes, the other smaller seedling is doing fantastically well: it's budding, thriving, and doesn't seem afflicted by anything at all, thank god)
     

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  2. fern2

    fern2 Active Member

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    Doesn't anybody have any ideas about my poor little arbutus?

    I assume its got some kind of leaf spot fungus (& maybe a few shield bearers thrown in for good luck) and, if that's what it really is, I know that it probably won't be lethal. But I'd like a second opinion, just in case I'm wrong.

    I'd also be grateful for any ideas you guys might have for curing the fungus, even if you can't identify which species it is. Should I put an anti-fungal agent on the leaves (not soil)? Spritz some compost tea on the leaves? Add healthier arbutoid mycorrhizae from the dirt around my happy seedling? Or do I just cross my fingers & hope that the fungus dies back over the summer?

    HELP!
     
  3. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

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    The person at the garden who is most likely able to answer this question is on vacation. I'll forward the link to his attention for when he returns.
     
  4. fern2

    fern2 Active Member

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    Thanks!!
     
  5. Stansgig

    Stansgig Member

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    Has anyone provided a solution to the initial question on how to treat insect infestation and fungus on the arbutus tree?

    It's April 2007 and I spotted an over-infestation of aphids on my two mature 7' tall arbutus marina. Every leaf is infected, new buds are covered with aphids. I am seriously tempted to spray my trees with chemicals. Please help, how do I save my trees?

    (We only live in this home in Northern CA since the early fall 2006, thus I do not know if this is common spring occurance.) These trees were healthy, had magnificant blooms and berries in the fall, now this.

    We had far less rain this winter and more than usual amount of rain last winter. I cut off tips of several branches which were blocking the path to our entrance in the late fall and I watered a little during winter's dry periods.
     
  6. fern2

    fern2 Active Member

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    Hey,

    No, I don't think anyone ever did. Both of my arbutus seedlings are STILL struggling with various infestations & infections: aphids (of course), a bit of scale & the occasional whitefly, probably some unseen soil-based fungi, and most recently what seems to be a complete lack of nutrient flow to the top branch & leaves of one of the plants.

    For the 'invisible' pests (=fungi etc), the best suggestion I've read has been to use compost tea on the leaves & even the soil to overpower any bad fungi/bacteria with a whole lot of good ones. Unfortunately I don't have the time/supplies to make my own tea (& don't know where to buy it) so I haven' t been able to test out that theory.

    My solution to the 'visible' attackers (=insects) has simply been to physically remove them from the plants by hand every 3-20 days, depending on their numbers - I use a kleenex & just wipe/squish'em off the plants. It's a pain but I don't want to risk using chemicals (even soapy water) since arbutus roots are so reliant on arbutoid mycorrhizae (='good' fungus) and any pesticides or fungicides, even on the leaves, could seriously impact the plants themselves.

    But I guess that if you're dealing with 7' trees & a really serious infestation like the one you described, it won't be very easy to pick off all the aphids by hand. You might want to put up sheets of sticky tape (to catch the flying aphids). Or plant some marigolds, dill, angelica, morning glory or fennel nearby to attract their predators - or basil to repel the aphids themselves. However, I think your very best solution, especially for such a big infestation, would be to get yourself some 'beneficial insects' like ladybugs & lacewings: http://tfpg.cas.psu.edu/349.htm. You can order them online or find them in a local garden supply store. I think I'll probably do the same, especially for my patch of lupins which ALWAYS gets covered in the most disgustingly huge aphids all summer long... you can practically hear them munching & vibrating from across the garden. Yuck!!

    Good luck!

    PS: if anyone out there has an idea why my once happy arbutus looks like it's not getting any nutrients to its leaves, please let me know!! It's really painful to watch it decline like this...
    Thx.
     
  7. Arbcoll

    Arbcoll Member

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    Hi,
    No promises on success, what works for one doesn't always work for another, but a few suggestions from good (and bad) experience.
    If the leaves are bad the seedlings ability to draw up nutrients will be impaired anyway so good and bad fungus cancels out, and a weakened tree is then more susceptible to bad than good (cause and effect), it gets worse and will almost inevitably be beaten. For leaf spot, which Arbutus are prone to, you could try one of the leaf sprays for rose black spot - not a systemic "water in" (in UK we have Rose Clear - this does seem to help). If the seedlings are big enough and have healthy leaf buds formed you could defoliate (and burn what you remove) - it may seem drastic but it can be a case of "being cruel to be kind" and the seedling should be pushed into new, hopefully healthier growth, and it is at least the right time of year. For aphids, surround the seedling with some bright tasty flowering annuals that will attract hover-flys, wasps, ladybirds etc. Some aphids will relocate and the predators drawn in should help control the rest. Have you checked the soil and root system for weevils? Lack of roots could be a problem if you have these nasties. Lastly is the compost that they are in healthy? Add some lime-free grit (20%) to help drainage and root formation and a little charcoal to keep it sweet. Good luck.
     
  8. Stansgig

    Stansgig Member

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    Thank you both for the information. I'll check the soil for any clues. And add few more containers with flowers to attract predators.

    I border to a Sibley regional park where I volunteer. I definitely noticed a lot of lady bugs in the park land this morning, where we removed non-native blooming french broom.

    I sought an advice from our park ranger. He suggested to spray the trees with a safer soap due to the massive infestation. In less of an infestation he would prefer that I hose down with water to discourage the aphids.

    However, the nursery owner from just down the hill, suggested a Paraffinic oil spray.

    Any of you have experience with either of the products?
     
  9. growest

    growest Active Member 10 Years

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    The safer's soap works well on aphids...these are pretty easy to kill.

    The tip of plant that seems to get no nutrients...you may be seeing winter injury. I had one of my seedlings do this thanks to the Nov. quick and early cold snap, the new growth will have to start again from beneath this dead portion of stem. You could cut back to good healthy stem if you like.

    The spotted, ragged leaves are common with these, generally I just hope to grow the plants as quickly as possible to outgrow the bad guys. The other trick is to keep potted plants out of the rain, at least in the winter. Microbes have a hard time establishing if the foliage stays dry. This is not usually an issue during the spring and summer, but our continual winter rains do encourage the leaf spots.

    These are difficult plants to grow, esp. in containers, maybe that will be encouraging!?
     
  10. Stansgig

    Stansgig Member

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    Thank you for your response. Getting ready to spray the trees this morning. The winds have calmed down by us.
     
  11. Arbcoll

    Arbcoll Member

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    Like Growest's comments on the safer's soap. the parafinnic oil spray would also help to clear the adult aphids and any scale insect (also good for woolly aphid or meally bug) and I have used it on pines to clear heavy aphid infestations - If the tree is small enough I use a water or soap spray first to clean up the tree a bit and remove "soot" caused by the aphid secretions. The soap or oil are two good ways to the same goal, if one doesn't work, try the other.

    Growest also makes a good point about winter damage, in the UK my Arbutus menziesii suffer badly each winter from late cold snaps with up to 50% of the leaves being burned brown, and some loss of late growth. And there is a valley that funnels the winter winds across the garden so 100% of the leaves get torn, but they bounce back each year once the new growth gets going.
    Looking at the pics again, one or two of the leaves look like they could be the work of bees removing sections for nests?
     
  12. Stansgig

    Stansgig Member

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    Thank you for the info on paraffinic oil spray. My local nursery supplier sold me Master Nursery brand. I sprayed the larger of the trees with the paraffinic oil and just hosed down the smaller ones. The nursery guy instructed me to repeat the spray 2 more times 7 days apart. Is that necessary?

    Also, is it OK to hose off the tree sprayed with paraffinic oil with water in between the oil applications? Master Nursery website does not offer much help on the product.
     
  13. Arbcoll

    Arbcoll Member

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    The oil works physically and directly on the adult aphids, it coats them, so will hit the ones that are active when you spray, but it is unlikely to catch them all. Any that are left will lay more which is why they recommend a couple of repeat spray at 5-7 day intervals. Hosing off after a day or two shouldn't make much difference and will help keep the foliage clean. Paraffinic oil and the soap have been around a long, long time.
     
  14. Stansgig

    Stansgig Member

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    Thanks, again.
     

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