What are these tiny green lumps on my tree?

[Tina_z]

Hi guys, I am new to this forum and also to gardening in general. Have a question about one of our trees in the backyard.

As circled in the photos, there are a lot of tiny green lumps clustered around the base of the branches on our flowering plum tree. (I think it is plum according to the flowers, though it has never had fruits for 3 years.) The tree was having issues with aphid and ant infestation before, and not very healthy, but this year it looks improved, and we are hoping it will be able to bear fruits. But I am really concerned about these lumps, as we have another healthy plum tree nearby, and it doesn't have it. Is it related to aphids or is it something else? What should I do to treat it?

Thanks for your help!

 

[Chuck]

Hi guys, I am new to this forum and also to gardening in general. Have a question about one of our trees in the backyard.

As circled in the photos, there are a lot of tiny green lumps clustered around the base of the branches on our flowering plum tree. (I think it is plum according to the flowers, though it has never had fruits for 3 years.) The tree was having issues with aphid and ant infestation before, and not very healthy, but this year it looks improved, and we are hoping it will be able to bear fruits. But I am really concerned about these lumps, as we have another healthy plum tree nearby, and it doesn't have it. Is it related to aphids or is it something else? What should I do to treat it?

Thanks for your help!

I am not positive about this but it looks like the beginning stages of Black Knot Disease. It starts with a greenish gall like structure at the base of twigs and even on the actual limbs and trunk as shown in the second picture. I didn't think BKD was in Calif. It is prevalent in the east and fairly common there. This disease if left untreated can cause serious loss of fruit production. To make sure of what is happening to your tree I would contact your extension agent or some other local expert. Some varieties of plum trees are resistant to this disease which is why your other tree is not showing symptoms. This is a fungal disease and is spread by wind and rain.

 

[Marck]

Greetings, welcome to the Forums.

Please take a sharp, close-up shot of the bumps in good light. Use the Macro setting on your camera.

 

[Tina_z]

I am not positive about this but it looks like the beginning stages of Black Knot Disease. It starts with a greenish gall like structure at the base of twigs and even on the actual limbs and trunk as shown in the second picture. I didn't think BKD was in Calif. It is prevalent in the east and fairly common there. This disease if left untreated can cause serious loss of fruit production. To make sure of what is happening to your tree I would contact your extension agent or some other local expert. Some varieties of plum trees are resistant to this disease which is why your other tree is not showing symptoms. This is a fungal disease and is spread by wind and rain.

Thanks Chuck! I think you are right. I was not sure because the photos online for BKD are black while mine is green and way smaller.
Looks like the best way to treat it is just to cut off all infected branches and spray fungicide. Our tree is heavily infected so I don't know if there will be enough branches left for it to survive. At least we caught it early before it becomes wrose. Hope the tree will recover...

 

[Tina_z]

Greetings, welcome to the Forums.

Please take a sharp, close-up shot of the bumps in good light. Use the Macro setting on your camera.

Hi Marck is this photo better? It is from a branch we cut off.

 

[Marck]

This is Plum Bud Gall Mite (Acalitus phloeocoptes), an emerging pest problem in California. Read all about it.
https://mgsantaclara.ucanr.edu/files/300211.pdf

Treatment options include predacious mites, sulfur, and pesticide use, but it sounds like the efficacy of these treatments is still being determined.

Amazingly, one can still get a healthy crop from an infested tree, though yield and vigor may be affected.

 

[Tina_z]

This is Plum Bud Gall Mite (Acalitus phloeocoptes), an emerging pest problem in California. Read all about it.
https://mgsantaclara.ucanr.edu/files/300211.pdf

Treatment options include predacious mites, sulfur, and pesticides use, but it sounds like the efficacy of these treatments is still being determined.

Amazingly, one can still get a healthy crop from an infested tree, though yield and vigor may be affected.

Wow. I read this article and also searched online. I think it is more likely Plum Bud Gall Mite than BKD. Can't believe it is only discovered in 2019 in California. How did you know about this?

I will follow the recommendation and call our local department to see what they suggest. Thanks Marck.

 

[Tina_z]

Updates:
Called local department, they directed me to the same website. I used Sulfur treatment on the tree twice, looks like the Plum Bud Gall Mite didn't get wrose, and the fruits are growing ok.