Strange white fungus/mold on magnolia stems

3 years ago

last modified: 3 years ago

We have a large magnolia bush near our driveway. It's somewhere between 20-30 years old (can't remember exactly how old it is) and in all the years we've had it I've never seen anything like this. Not sure if this is related, but there are lots of wasps/hornets (some kind of bee) flying around this shrub constantly even though it's not blooming right now. I was looking for a hive/nest today in the bush but did not see one (although it's possible I just didn't see it). There also appears to be some sort of sticky substance on our driveway near the bush. Does anyone have any idea what's going on? Also, does this need to be treated or is this a cosmetic issue of some sort?

Forgot to say I don't know exactly what kind of magnolia this is, but it has pink flowers on it.

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Comments (13)

floral_uk z.8/9 SW UK
3 years ago
Pix are really needed but in the meantime look at images of Magnolia scale. The sticky substance would be honeydew, the excrement of aphids, scale insects etc.
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gardengal48 (PNW Z8/9)
3 years ago
Even without photos, I'd bet money on it being magnolia scale!! It is very common on various species of deciduous magnolia and seems to be rampant this year.....we have already had several recent posts reporting the same thing.

The wasps are going after the honeydew.
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I'm afraid I disagree with pretty much everyone. I would say its fungal (sclerotinia maybe), caused by too much moisture and not enough ventilation (and of course spores). The thinner diameter is indicative of the cell walls breaking. Is it harder there than in the green areas? Woody, I mean? As the plant grows the stem will get thicker. It looks to me that the plant persevered over the sclero rot. It's unbelievably common in greenhouses and it's commonly overcome. No chemical treatment will stop an established infestation as far as I know. Rockwool is good for sclero and pythium. It maintains a constant humidity around the base. Using perlite and coco seems to work better for me. Sclerotinia can cause the stem to become woody and thus reduce water flow. This can reduce yields or even lead to further complications down the road. Obviously reduced water intake is going to cause problems. I had a few plants that suffered this when young, but they pulled out of it. But, they produced less and smaller fruit. Still enough for us, so it wasn't a big deal. The stems stayed thinner at the base and I'm guessing the bottle neck is what caused the reduced yield. Those plants were in rockwool. In fact, I have a bunch of rockwool starter cubes here if anyone lives near New Whiteland, IN. I won't use them because of this problem and the higher rate of damping off. There are cheaper, superior alternatives. If I were you, I would keep these plants going, but consider an alternative method later to see the difference. If it weren't for the thin section, I would then have also said it was salt buildup. I get that a lot, but not with the thinning, scabbing issue.
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If it's that's infested, yes cut it back. Unfortunately I know of no fast scale predators. There are excellent controls, but they can take some time to work, and with a heavy infestation you may not have that time. A large enough release to try and make up for the size of the infestation would be expensive, and might not be successful if you don't get the right predator for the type of scale you have. What I would do: Cut back tree Get a definite ID on the type of scale you have - this may require some very close-up macro shots on what is a pretty tiny insect. If you don't have a camera that can get a small enough depth of field, see if you can find an entomology school near you, or check Bug Guide for people who may take a specimen for ID. Once you know what you're dealing with, buy the best predator for it and make multiple releases in your yard over the growing season. It may take several years to build up enough of a stable enough population that you could relax your guard a little. You may be able to do without the definite ID, but because its scale and the predators for scale can be specifically selective sometimes, I would get one. #1 predator - Ladybeetles! Some good species to try (commonly used in horticulture around the US): Cryptolaemus montrouzieri (primarily a mealybug predator, but they like scale too). aka Crypts Rhyzobius lophanthae, aka Singular Black Ladybeetle Cybocephalus nipponicus - not really a Ladybeetle, but in the same Superfamily And a parasitic micro-wasp: Metaphycus helvolus All of these things will take time to take hold and take a population down, as I said. They are preventatives and maintenance once the main infestation is gone and you need to keep up with them once scale starts in your yard. It's a tough pest to deal with. Oh, whatever you do use, don't use common Asian Spotted Ladybeetles - Harmonia axyridis. They fly away from your yard after you release them, so do little good in the end. They're great to have in the environment in general, so are good to release as a general environment beneficial, and eventually you may see them and their larvae come visit a problem area you have, but that's it.
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That is definitely not blossom end rot. It looks like a fungal organism that produces sclerotia. Is there a fuzzy white "mold" around/before the grains develop? Also, check the base of the affected plant right at the soil line. If you have mulch, move it aside so you can see clearly. Is there any fuzzy white material there? Any little round grains about the size of mustard seeds?
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Hi and welcome to the forum :) I'm making an assumption here but it looks like you used pure bagged mix for those plants? I don't know if that's the case, but it's most likely the root cause of the plants dying. (no pun intended) The pure mix will drain very fast and become hydrophobic (meaning it won't hold water anymore) in our summers. That white stuff is fungus that has grown from the excessive watering that that type of soil would need to keep even a little moisture in it. Plus the surrounding soil would become very bog-like and contribute to the fungus. Some types of fungus in the soil aren't bad for plants, but with that much fungus the conditions were probably ideal for lots of bacteria to thrive too. You want to mix that bagged stuff with native soil when you plant something, even in raised beds (not containers though, but that's a different topic). The *most* I will add to soil is about 50% compost (depending on how fine it is), and that's for something that needs very fast draining soil (not fruit trees), and the soil will be shaded by something, and the ground will have lots of mulch applied to it. Usually annuals like Pumpkins or root vegetables will grow well in this type of mix. Otherwise I use around 10-25% compost or none at all. You may still be able to save the trees. I would wash all the roots off, remake the soil for the planting area with lots of native soil and very little compost added. You don't need to do this, but if I had extra time I would bake that mix (put it under a clear plastic sheet out in the sun for a few weeks) before I used it again, otherwise I'd just buy new mix.
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ken_adrian Adrian MI cold Z5
3 years ago
could also be lichens .... but that wouldnt explain the wasps ... or some of both ....

lichens are entirely harmless .. and usually an indicator of good air quality ....

https://duckduckgo.com/?t=ffcm&q=lichens&iax=images&ia=images

ken
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gardengal48 (PNW Z8/9)
3 years ago
Lichens do not create honeydew nor do they attract wasps. Lichens may well be present but they are NOT the issue.
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ken_adrian Adrian MI cold Z5
3 years ago
pretty sure thats what i said ... but they shouldnt bother trying to kill the lichens .. if any
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Smivies (Ontario - 5b)
3 years ago
Lichens also don't pop when you squeeze them...be careful, that stuff will stain clothing.
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perennialfan275
Original Author
3 years ago
If it is this magnolia scale you guys are talking about, what should be done about it, if anything?
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bellarosa
3 years ago
It sounds like insect scale. The scales secrete a sweet substance that attracts bees and wasps, so be careful. My magnolia has the same thing - see pics below. My tree is at least 20 years old and over 20 feet tall.

I had a company come out today that specializes in the treatment of insect scale. They promised a quote next week. They recommended 4x treatments - 3 applications this year in the Fall (I think it's of a systemic insecticide) and 1 application in the Spring of dormant oil. I hope other folks who have had this similar issue can chime in on this. I'm curious to know what the success rate is. It's definitely not going to be cheap to eradicate this.
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ken_adrian Adrian MI cold Z5
3 years ago
absolutely scale .... with some little lichens.. hard to confuse them.. when you get down to it ...

i dont understand why you would need repeated applications of a systemic ... any chance they gave you something in writing???

are you able to get a coupe more quotes???

ken
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Smivies (Ontario - 5b)
3 years ago
"They recommended 4x treatments - 3 applications this year in the Fall (I think it's of a systemic insecticide) and 1 application in the Spring of dormant oil."

We had one trunk injection of systemic late June last year and remain scale free this year. I expect we'll have to repeat ~2-3 years from now when birds drop off new crawlers and the scale numbers build up again.
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Marie Tulin
3 years ago
My beautiful yellow magnolia was heavily infested with scale last year. The arborists sprayed last fall and again this spring.when the insects were at the "crawling" stage. I just noticed a part of the tree is still affected and I'm about to call again.

They didn't mention injections.....I'm going to ask about that....
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perennialfan275
Original Author
3 years ago
So I googled magnolia scale, and after comparing it with my shrub this indeed appears to be the issue. I also read about people using neem oil to treat this. Has anyone used neem oil for this in the past and if so how effective was it?
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bellarosa
3 years ago
Ken, no, I did get another quote. There was another company that I had in mind, but their review on yelp was awful! The company I'm considering going with has great reviews and feedback for multiple folks.
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Strange white fungus/mold on magnolia stems

Comments (13)

floral_uk z.8/9 SW UK

gardengal48 (PNW Z8/9)

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Strange white fungus/mold on magnolia stems

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