Help with my JM! Can't figure out what is wrong. PIC

[Alex W.]

Hi Everyone,

I have a 17 year old japanese maple that I got from a local bonsai nursery back in February. The tree has shown steady growth and was constantly sprouting new leaves, however I've recently discovered some leaves falling off more than usual. Upon cleaning up the fallen leaves, I noticed some black spots on the undersides. My initial thought was black aphids, but the spots resemble a TAR like substance that is a little sticky. Also, up close, these spots do not look like black aphids at all. Again, they look like tar spots.

Has anyone seen this before and what kind of treatments should I try?

I live in Los Angeles (about 1 mile from the ocean) where temperatures are 75-80 in the day and mid 60s at night. (Zone 5??)

 

[StarGazer]

looks like a fungus, or soothy mold from scale insect excretions. I've seen soothe mold in wild Quercus (oak) in cloud mountain forests, not JMs. Can you zoom in on a leaf, it's hard to see the details of the black dots.

have you been watering the tree? The leaves also look dry.
it's possible the recent heat wave and ashes from the fires are affecting its health.

 

[Alex W.]

Thank you for your quick reply! Yep! Watering once a day.
Here are some closeups. The last pic is after I scraped some off with my fingernail.
I know, it looks like aphids on the stem, but scrapes off like crust

 

[StarGazer]

It does look like sooty mold from insect excretion. In Quercus, the scale insect will feed on sap of a tree and excrete a sugary waste (honeydew), leading eventually to the sooty mold which uses the sugars from the honeydew for growth.
Aphid infestation can also lead to sooty mold.
You could try rinsing the tree (keeping it away from all other trees) to remove all the mold and aphids, which will affect photosynthesis, and eventually the health of the tree if left unchecked.
Clean any tools used in this tree with alcohol to prevent contamination to other trees, in case its a fungus, bacteria or viral disease.
There are oil sprays, such as neem oil, sold for treatment of aphids, the wild basically prevents the insect from breathing, so it need to get in contact with the insect. I also use oils for treating scale insects when they are in the non-scale stage.
In addition, I proactively treat my trees by maintaining colonies of praying mantis and ladybugs, predatory insect that feed on aphids, worms, caterpillars etc.

 

[Shibui]

Could these be scale insects? It is not a scale I am familiar with but appears to have all the hallmarks of scale infestation. Check to see in the crusts have soft, squishy things underneath. Scale insects make an armor plated shell to hide under as protection from predators while they enjoy sucking the juices from your plant.
Horticultural oils or the older 'white oil' are usually recommended for scale. Newer oil based sprays seem to be safer and more effective. As @StarGazer mentions oil based insecticides cover the insects and suffocate them but rely on thorough coverage of ALL surfaces to be effective. You usually need to repeat treatment several times to get all the bugs and to get any newly hatched ones. Check warnings on the container. Oils can damage leaves if used in hot weather.
Some of the newer systemic insecticides also deal with some scales and as they move right through the plant any insect that sucks or bites it dies so thorough coverage is not so important but there is concern over non target species being affected.

 

[sorce]

Is there any uniformity or growth?

I had some pots sitting well away from plants on my table and they were getting spots like this.

It looked like iron spotting, I thought, "I don't remember that dot", then it wiped off.



Sorce

 

[Mapleminx]

Hows it doing now?

 

[Mike Corazzi]

Jeez, I hate to harp on this but....

Bayer Tree & Shrub Protect & Feed.



SYSTEMICALLY ....ends... ALL aphid and scale problems.

While..... feeding the tree.

 

[Flowerhouse]

Jeez, I hate to harp on this but....

Bayer Tree & Shrub Protect & Feed.

View attachment 331490

SYSTEMICALLY ....ends... ALL aphid and scale problems.

While..... feeding the tree.

The active ingredient in Bayer (imidacloprid) doesn't work on all scale insects.

"Soil Applied Systemic Insecticides: Although soil treatments with common products containing imidacloprid will control some tree and shrub pests, such as soft scales, aphids and white flies, these products do little to control armored scales. In fact, treatments with imidacloprid may very well increase populations of spider mites on the plants in the summer."

Armored Scale Insects & Control

Learn how to identify armored scale infestations and protect your plants.

hgic.clemson.edu

I realize that what Alex W is dealing with isn't an armored scale. Still, ALL generally means all.

 

[Mike Corazzi]

The active ingredient in Bayer (imidacloprid) doesn't work on all scale insects.

"Soil Applied Systemic Insecticides: Although soil treatments with common products containing imidacloprid will control some tree and shrub pests, such as soft scales, aphids and white flies, these products do little to control armored scales. In fact, treatments with imidacloprid may very well increase populations of spider mites on the plants in the summer."

Armored Scale Insects & Control

Learn how to identify armored scale infestations and protect your plants.

hgic.clemson.edu

I realize that what Alex W is dealing with isn't an armored scale. Still, ALL generally means all.

The scale I ....WAS... getting on my olives was hard, scrapey-offey hard blisters of scale.
I have had none since using that stuff.

 

[Leo in N E Illinois]

I would have said you have tar spot fungus. Any of the generic fungicides will help with new infections, but old infections, the damage will last as long as the leaf does. Mancozeb, Daconil, Cleary's 3336, or its Bonide equivalent, all 3 are useful. The timing of fungicides should be to applied about 3 to 6 weeks you first saw these black spots appear. Make a note and apply a prophylactic dose next year. Tar spot is rarely fatal, it winters over in the dead leaves. Collect and destroy the dead leaves with tar spot. The fungus usually does not overwinter in the maple itself, mainly in the dead leaves. Spores released in late spring or early summer. Fungicide treatment should be about the time of spore release. You may need to do some digging, internet searching to get the timing down for your micro-climate.

If it is scale insects, then the Bayer Tree & Shrub will work. Note it works on insects. Spider mites are not insects, they are arachnids, spiders, and one needs to use a product labelled for spider mites. The Bayer product is fairly effective. They have been adding adjuvants to help prevent insect resistance. It should still work pretty well.

No pesticide is totally safe, or totally harmless. As always read the label and apply according to directions.

 

[Bonsai Nut]

I would have said you have tar spot fungus.

My vote.

My anti-fungal mix is Heritage, Cleary's 3336, Mancozeb. I would apply during the rainy season, 10 days between application, prophylactically.

 

[Alex W.]

Update!
took it to my local bonsai nursery for some extra eyes and the conclusion was that it was a fungus (probably tar spot ) that built up due to excess heat and moisture. After a detailed search, no pests were found anywhere. I decided to cut off all leaves, spray fungicide and let it all grow back. Hopefully this episode is over and she comes back!

 

[ConorDash]

Its not too late in your climate, to fully defoliate a tree?

 

[PA_Penjing]

@ConorDash California is a weird place, i don't know if that guy even has a winter haha. The coldest winter nights there hit 4 or 5 degrees celsius