CamperDown Elm Black spot?

Asked July 14, 2018, 2:29 PM EDT

Hello... We have a two year old Camperdown Elm tree. Last year we did not have any issues with it. This year, however, is a different story. We are educating ourselves online, with the Elm tree diseases, but it seems we are just moving in circles without any real definitive direction. About 2 weeks ago we noticed what looked like aphids all over the tree...lots of them, curling the leaves, etc. I removed the heavily infested leaves, put them in a sealed container and through them away. I then sprayed our tree heavily with Neem Oil. We did that twice. Now, there is black spot all over the leaves...inner canopy mostly...but outer as well. There is new growth that doesn't have this black spot. The leaves with spots on them eventually turn yellow and fall off. I have pulled off all the yellow leaves. They just practically fall off. I have gathered all of these leaves, as well as the ones on the ground and sealed them and thrown them away as well. We have sprayed our tree with Neem Oil/horitcultural oil twice for this, a week apart. Holy Smokes...what is going on with our tree. We really love this tree and want to give it all the best chances of being happy here. Are we doing the right thing. We don't want to lose this tree...Please help...advice, diagnosis, etc!! Thank you, (P.S...we live 2 miles inland from the coast...plenty of warm weather) Heidi and Doug

Lincoln County Oregon

3 Responses

You are doing all the right things now. Our warm temperatures and higher humidity could be providing fungi like Black Spot a more favorable growing environment. Your removal effected leaves from the tree and from the ground (and disposal of them in the garbage). removes some sources of potential reinfection by spores that might over winter in the leafy debris. That said, fungal spores are distributed by wind, rain, & insects so they could still could get on the tree leaves again from another source.
You could also improve air circulation and sunlight penetration by selectively pruning some branches. This could help minimize fungal spread in the interior part of the canopy. One important thing to do is to ensure the tree is adequately hydrated so it doesn't become stressed. Normally, healthy trees can withstand these fungal attacks.

Next spring, as the leaves open, you could also apply Neem oil or a fungicide to try to prevent a fungal outbreak from occurring. It needs to be done then because once fungi get going, it is difficult to control.

Thank you, thank you.

How often should we spray with neem oil? Our tree is only 2 years old. I am very good about watering but it is possible that it didnt get enough. When watering, should I keep from getting the leaves wet? Do you believe this is black spot?
Could the tree actually die? It is crazy, but we really do get attached to all of our trees and plants.

It appears that it might be some type of black spot (possiblly Gnomonia or Stephora). Normally, otherwise healthy trees can withstand this. Like I said, keep the tree from becoming stressed. Water (irrigate the ground) once per week during the growing season unless we get rain. Don't overwater it. Next spring when leaves start opening, consider spraying with Neem Oil a couple times 10 days to two weeks apart. Hopefully, next year's conditions will be less conducive to fungal growth.